Asthma
Encyclopedia
Asthma is the common chronic
inflammatory disease
of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm
. Symptoms include wheezing, coughing, chest tightness, and shortness of breath. Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in 1 second (FEV1
), and peak expiratory flow rate. Asthma may also be classified as atopic
(extrinsic) or non-atopic (intrinsic).
It is thought to be caused by a combination of genetic
and environmental factors. Treatment of acute symptoms is usually with an inhaled short-acting beta-2 agonist (such as salbutamol
). Symptoms can be prevented by avoiding triggers, such as allergens and irritants
, and by inhaling corticosteroids. Leukotriene antagonist
s are less effective than corticosteroids and thus less preferred.
Its diagnosis is usually made based on the pattern of symptoms and/or response to therapy over time. The prevalence of asthma has increased significantly since the 1970s. As of 2010, 300 million people were affected worldwide. In 2009 asthma caused 250,000 deaths globally. Despite this, with proper control of asthma with step down therapy, prognosis is generally good.
as "a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. The chronic inflammation is associated with airway hyperresponsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness and coughing particularly at night or in the early morning. These episodes are usually associated with widespread, but variable airflow obstruction within the lung that is often reversible either spontaneously or with treatment".
Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in 1 second (FEV1
), and peak expiratory flow rate. Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic).
While asthma is classified based on severity, at the moment there is no clear method for classifying different subgroups of asthma beyond this system. Within the classifications described above, although the cases of asthma respond to the same treatment differs, thus it is clear that the cases within a classification have significant differences. Finding ways to identify subgroups that respond well to different types of treatments is a current critical goal of asthma research.
Although asthma is a chronic
obstructive
condition, it is not considered as a part of chronic obstructive pulmonary disease
as this term refers specifically to combinations of disease that are irreversible such as bronchiectasis
, chronic bronchitis
, and emphysema
. Unlike these diseases, the airway obstruction in asthma is usually reversible; however, if left untreated, the chronic inflammation of the lungs during asthma can become irreversible obstruction due to airway remodeling. In contrast to emphysema
, asthma affects the bronchi, not the alveoli.
.
, and chest tightness. While these are the primary symptoms of asthma, some people present primarily with cough
ing, and in severe cases, air motion may be significantly impaired such that no wheezing is heard.
Signs which occur during an asthma attack include the use of accessory muscle
s of respiration (sternocleidomastoid and scalene muscles
of the neck), there may be a paradoxical pulse
(a pulse that is weaker during inhalation and stronger during exhalation), and over-inflation of the chest. A blue color
of the skin and nails may occur from lack of oxygen.
In a mild exacerbation the peak expiratory flow rate (PEFR) is ≥200 L/min or ≥50% of the predicted best. Moderate is defined as between 80 and 200 L/min or 25% and 50% of the predicted best while severe is defined as ≤ 80 L/min or ≤25% of the predicted best.
Insufficient levels of vitamin D are linked with severe asthma attacks.
, in Atlanta, Georgia, U.S., showed that 15% had been diagnosed with asthma, and that 10% were on asthma medication.
There appears to be a relatively high incidence of asthma in sports such as cycling
, mountain biking, and long-distance running
, and a relatively lower incidence in weightlifting and diving. It is unclear how much of these disparities are from the effects of training in the sport.
Exercise induced asthma can be treated with the use of a short-acting beta2 agonist.
(2004) suggest that 15–23% of new-onset asthma cases in adults are work related. In one study monitoring workplace asthma by occupation, the highest percentage of cases occurred among operators
, fabricators, and laborers (32.9%), followed by managerial and professional specialists (20.2%), and in technical, sales, and administrative support jobs (19.2%). Most cases were associated with the manufacturing
(41.4%) and services (34.2%) industries. Animal proteins, enzymes, flour
, natural rubber latex
, and certain reactive chemicals are commonly associated with work-related asthma. When recognized, these hazards can be mitigated, dropping the risk of disease.
ing, and use of accessory muscle. Symptoms are often worse at night or in the early morning, or in response to exercise or cold air. Some people with asthma only rarely experience symptoms, usually in response to triggers, whereas other may have marked persistent airflow obstruction.
Studying the prevalence of asthma and related diseases such as eczema
and hay fever
have yielded important clues about some key risk factors. The strongest risk factor for developing asthma is a history of atopic disease
; this increases one's risk of hay fever by up to 5× and the risk
of asthma by 3–4×. In children between the ages of 3–14, a positive skin test for allergies
and an increase in immunoglobulin E
increases the chance of having asthma. In adults, the more allergens one reacts positively to in a skin test, the higher the odds of having asthma.
Because much allergic asthma is associated with sensitivity to indoor allergens and because Western styles of housing favor greater exposure to indoor allergens, much attention has focused on increased exposure to these allergens in infancy and early childhood as a primary cause of the rise in asthma. Primary prevention studies aimed at the aggressive reduction of airborne allergens in a home with infants have shown mixed findings. Strict reduction of dust mite allergens, for example, reduces the risk of allergic sensitization to dust mites, and modestly reduces the risk of developing asthma up until the age of 8 years old. However, studies also showed that the effects of exposure to cat and dog allergens worked in the converse fashion; exposure during the first year of life was found to reduce the risk of allergic sensitization and of developing asthma later in life.
The inconsistency of this data has inspired research into other facets of Western society and their impact upon the prevalence of asthma. One subject that appears to show a strong correlation is the development of asthma and obesity
. In the United Kingdom and United States, the rise in asthma prevalence has echoed an almost epidemic rise in the prevalence of obesity. In Taiwan, symptoms of allergies and airway hyper-reactivity increased in correlation with each 20% increase in body-mass index. Several factors associated with obesity may play a role in the pathogenesis of asthma, including decreased respiratory function due to a buildup of adipose tissue (fat) and the fact that adipose tissue leads to a pro-inflammatory state, which has been associated with non-eosinophilic asthma.
Asthma has been associated with Churg–Strauss syndrome, and individuals with immunologically mediated urticaria may also experience systemic symptoms with generalized urticaria, rhino-conjunctivitis, orolaryngeal and gastrointestinal symptoms, asthma, and, at worst, anaphylaxis. Additionally, adult-onset asthma has been associated with periocular xanthogranulomas.
s have been associated with asthma development and morbidity in children. Recent studies show a relationship between exposure to air pollutants (e.g. from traffic) and childhood asthma. This research finds that both the occurrence of the disease and exacerbation of childhood asthma are affected by outdoor air pollutants. High levels of endotoxin
exposure may contribute to asthma risk.
Viral respiratory infections are not only one of the leading triggers of an exacerbation but may increase one's risk of developing asthma especially in young children.
Respiratory infections such as rhinovirus
, Chlamydia pneumoniae and Bordetella pertussis
are correlated with asthma exacerbations.
Psychological stress has long been suspected of being an asthma trigger, but only in recent decades has convincing scientific evidence substantiated this hypothesis. Rather than stress directly causing the asthma symptoms, it is thought that stress modulates the immune system to increase the magnitude of the airway inflammatory response to allergens and irritants.
Beta blocker
medications such as metoprolol may trigger asthma in those who are susceptible.
, from traffic pollution or high ozone
levels, has been repeatedly associated with increased asthma morbidity and has a suggested association with asthma development that needs further research.
use early in life has been linked to development of asthma in several examples; it is thought that antibiotics make children who are predisposed to atopic immune responses susceptible to development of asthma because they modify gut flora
, and thus the immune system (as described by the hygiene hypothesis). The hygiene hypothesis
(see below) is a hypothesis
about the cause of asthma and other allergic disease, and is supported by epidemiologic data for asthma. All of these things may negatively affect exposure to beneficial bacteria and other immune system modulators that are important during development, and thus may cause an increased risk for asthma and allergy.
Caesarean section
s have been associated with asthma, possibly because of modifications to the immune system (as described by the hygiene hypothesis).
. In another study "the indoor concentration of aliphatic compounds (C8-C11), butanols, and 2,2,4-trimethyl 1,3-pentanediol diisobutyrate (TXIB) was significantly elevated in newly painted dwellings. The total indoor VOC was about 100 micrograms/m3 higher in dwellings painted in the last year". The author concluded that some VOCs may cause inflammatory reactions in the airways and may be the reason for asthmatic symptoms.
, , , NO
, aldehydes, RSP, and other VOC’s. The exposure concentration of is 18–35 ppbv, These numbers are significantly high and can had adverse effects on asthma. The inhalation of has an increased risk of respiratory symptoms and can change the lung function in children. According to the United States Environmental Protection Agency it is significantly important to use the exhaust fan when cooking with gas stoves to eliminate as many compounds from the air as possible.
The effects of on the respiratory system can be detrimental to one's health in a range of ways. In patients who are already asthmatic, lung function can decrease but non-asthmatic patients see no effects with concentrations under 1000 ppb. This article states that there is a dose-response relationship between and lung function; significant decrease in lung function at higher levels. The effects of from gas stoves, according to this study, are inconsistent and this is because the actual amount of was not measured. However, in the indoor environment, with the use of gas stoves for cooking, children had a 20% increase of asthmatic symptoms.
s have been associated with asthma in at least one genetic association
study. However, such studies must be repeated to ensure the findings are not due to chance. Through the end of 2005, 25 genes had been associated with asthma in six or more separate populations:
Many of these genes are related to the immune system or to modulating inflammation. However, even among this list of highly replicated genes associated with asthma, the results have not been consistent among all of the populations that have been tested. This indicates that these genes are not associated with asthma under every condition, and that researchers need to do further investigation to figure out the complex interactions that cause asthma. One theory is that asthma is a collection of several diseases, and that genes might have a role in only subsets of asthma. For example, one group of genetic differences (single nucleotide polymorphism
s in 17q21
) was associated with asthma that develops in childhood.
Research suggests that some genetic variants may only cause asthma when they are combined with specific environmental exposures, and otherwise may not be risk factors for asthma.
The genetic trait, CD14 single nucleotide polymorphism
(SNP) C-159T and exposure to endotoxin
(a bacterial product) are a well-replicated example of a gene-environment interaction that is associated with asthma. Endotoxin exposure varies from person to person and can come from several environmental sources, including environmental tobacco smoke, dogs, and farms. Researchers have found that risk for asthma changes based on a person's genotype
at CD14 C-159T and level of endotoxin exposure.
Home factors that can lead to exacerbation include dust
, house mites
, animal dander
(especially cat and dog hair), cockroach allergen
s and mold
s at any given home. Perfume
s are a common cause of acute attacks in females and children. Both virus
and bacterial infection
s of the upper respiratory tract infection can worsen asthma.
" —that the rise in the prevalence of allergies and asthma is a direct and unintended result of reduced exposure to a wide variety of different bacteria and virus types in modern societies, or modern hygienic practices preventing childhood infections. Children living in less hygienic environments (East Germany vs. West Germany, families with many children, day care environments) tend to have lower incidences of asthma and allergic diseases. This seems to run counter to the logic that viruses are often causative agents in exacerbation of asthma. Additionally, other studies have shown that viral infections of the lower airway may in some cases induce asthma, as a history of bronchiolitis
or croup
in early childhood is a predictor of asthma risk in later life. Studies which show that upper respiratory tract infections are protective against asthma risk also tend to show that lower respiratory tract infections conversely tend to increase the risk of asthma.
es in living quarters; these insects are more likely to be found in those same neighborhoods.
Most likely due to income and geography, the incidence of and treatment quality for asthma varies among different racial groups. The prevalence of "severe persistent" asthma is also greater in low-income communities than those with better access to treatment.
There is currently not a precise physiologic, immunologic, or histologic test for diagnosing asthma. The diagnosis is usually made based on the pattern of symptoms (airways obstruction and hyperresponsiveness) and/or response to therapy (partial or complete reversibility) over time.
The British Thoracic Society
determines a diagnosis of asthma using a ‘response to therapy’ approach. If the patient responds to treatment, then this is considered to be a confirmation of the diagnosis of asthma. The response measured is the reversibility of airway obstruction after treatment. Airflow in the airways is measured with a peak flow meter
or spirometer
, and the following diagnostic criteria are used by the British Thoracic Society
:
In contrast, the US National Asthma Education and Prevention Program (NAEPP) uses a ‘symptom patterns’ approach. Their guidelines for the diagnosis and management of asthma state that a diagnosis of asthma begins by assessing if any of the following list of indicators is present. While the indicators are not sufficient to support a diagnosis of asthma, the presence of multiple key indicators increases the probability of a diagnosis of asthma. Spirometry
is needed to establish a diagnosis of asthma.
The latest guidelines from the U.S. National Asthma Education and Prevention Program (NAEPP) recommend spirometry
at the time of initial diagnosis, after treatment is initiated and symptoms are stabilized, whenever control of symptoms deteriorates, and every 1 or 2 years on a regular basis. The NAEPP guidelines do not recommend testing peak expiratory flow as a regular screening method because it is more variable than spirometry. However, testing peak flow at rest (or baseline) and after exercise can be helpful, especially in young patients who may experience only exercise-induced asthma
. It may also be useful for daily self-monitoring and for checking the effects of new medications. Peak flow readings can be charted together with a record of symptoms or use peak flow charting software. This allows patients to track their peak flow readings and pass information back to their doctor or respiratory therapist.
Before diagnosing asthma, alternative possibilities
should be considered such as the use of known bronchoconstrictors (substances that cause narrowing of the airways, e.g. certain anti-inflammatory
agents or beta-blockers
). Among elderly people, the presenting symptom may be fatigue, cough, or difficulty breathing, all of which may be erroneously attributed to Chronic obstructive pulmonary disease
(COPD), congestive heart failure
, or simple aging.
can coexist with asthma and can occur as a complication of chronic asthma. After the age of 65 most people with obstructive airway disease will have asthma and COPD. In this setting, COPD can be differentiated by increased airway neutrophils, abnormally increased wall thickness, and increased smooth muscle in the bronchi. However, this level of investigation is not performed due to COPD and asthma sharing similar principles of management: corticosteroids, long acting beta agonists, and smoking cessation. It closely resembles asthma in symptoms, is correlated with more exposure to cigarette smoke, an older age, less symptom reversibility after bronchodilator administration (as measured by spirometry
), and decreased likelihood of family history of atopy
.
and asthma.
Pulmonary aspiration
, whether direct due to dysphagia
(swallowing disorder) or indirect (due to acid reflux), can show similar symptoms to asthma. However, with aspiration, fevers might also indicate aspiration pneumonia
. Direct aspiration (dysphagia) can be diagnosed by performing a modified barium swallow
test. If the aspiration is indirect (from acid reflux), then treatment is directed at this is indicated.
and after delivery, breastfeeding
, increased exposure to respiratory infection per the hygiene hypothesis
(such as in those who attend daycare or are from large families).
The most effective treatment for asthma is identifying triggers, such as cigarette smoke
, pets, or aspirin
, and eliminating exposure to them. If trigger avoidance is insufficient, medical treatment is recommended. Medical treatments used depend on the severity of illness and the frequency of symptoms. Specific medications for asthma are broadly classified into fast-acting and long-acting categories.
Bronchodilators are recommended for short-term relief of symptoms. In those with occasional attacks, no other medication is needed. If mild persistent disease is present (more than two attacks a week), low-dose inhaled glucocorticoids or alternatively, an oral leukotriene antagonist
or a mast cell stabilizer
is recommended. For those who suffer daily attacks, a higher dose of inhaled glucocorticoid is used. In a severe asthma exacerbation, oral glucocorticoids are added to these treatments.
s, smoke (tobacco and other), air pollution, non selective beta-blockers, and sulfite-containing foods.
Cigarette smoking and second hand smoke (passive smoke) in regard to people with asthma causes problems in effectiveness of management medications such as steroid/corticosteroid therapies.
Fast acting
Long term control
Delivery methods
Medications are typically provided as metered-dose inhalers (MDIs) in combination with an asthma spacer
or as a dry powder inhaler
. The spacer is a plastic cylinder that mixes the medication with air, making it easier to receive a full dose of the drug. A nebulizer
may also be used. Nebulizers and spacers are equally effective in those with mild to moderate symptoms however insufficient evidence is available to determine whether or not a difference exists in those severe symptomatology.
Safety and adverse effects
Long-term use of glucocorticoids carries a significant potential for adverse effects. The incidence of cataract
s is increased in people undergoing treatment for asthma with corticosteroids, due to altered regulation of lens epithelial cells. The incidence of osteoporosis
is also increased, due to changes in bone remodeling
.
For those with severe persistent asthma not controlled by inhaled corticosteroids and LABAs bronchial thermoplasty
can lead to clinical improvements. It involves the delivery of controlled thermal energy to the airway wall during a series of bronchoscopies
and result in a prolonged reduction in airway smooth muscle
mass.
; surveys show that roughly 50% of asthma patients use some form of unconventional therapy. There is little data to support the effectiveness of most of these therapies. Evidence is insufficient to support the usage of Vitamin C. Acupuncture
is not recommended for the treatment as there is insufficient evidence to support its use. Air ioniser
s show no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators.
Dust mite control measures, including air filtration, chemicals to kill mites, vacuuming, mattress covers and others methods had no effect on asthma symptoms. However, a review of 30 studies found that "bedding encasement might be an effective asthma treatment under some conditions" (when the patient is highly allergic to dust mite and the intervention reduces the dust mite exposure level from high levels to low levels). Washing laundry/rugs in hot water was also found to improve control of allergens.
A study of "manual therapies" for asthma, including osteopathic
, chiropractic
, physiotherapeutic
and respiratory therapeutic
manoeuvres, found there is insufficient evidence to support their use in treating. The Buteyko breathing technique for controlling hyperventilation may result in a reduction in medications use however does not have any effect on lung function. Thus an expert panel felt that evidence was insufficient to support its use.
For those who continue to suffer from mild symptoms, corticosteroids can help most to live their lives with few disabilities
. It is more likely to consider immediate medication of inhaled corticosteroids as soon as asthma attacks occur. According to studies conducted, patients with relatively mild asthma who have received inhaled corticosteroids within 12 months of their first asthma symptoms achieved good functional control of asthma after 10 years of individualized therapy as compared to patients who received this medication after 2 years (or more) from their first attacks. Though they (delayed) also had good functional control of asthma, they were observed to exhibit slightly less optimal disease control and more signs of airway inflammation.
Asthma mortality has decreased over the last few decades due to better recognition and improvement in care.
As of 2009, 300 million people worldwide were affected by asthma leading to approximately 250,000 deaths per year.
It is estimated that asthma has a 7-10% prevalence worldwide. As of 1998, there was a great disparity in the prevalence
of asthma across the world, with a trend toward more developed
and westernized
countries having higher rates of asthma, with as high as a 20 to 60-fold difference. Westernization however does not explain the entire difference in asthma prevalence between countries, and the disparities may also be affected by differences in genetic, social and environmental risk factors. Mortality however is most common in low to middle income countries, while symptoms were most prevalent (as much as 20%) in the United Kingdom, Australia, New Zealand, and Republic of Ireland; they were lowest (as low as 2–3%) in Eastern Europe, Indonesia, Greece, Uzbekistan, India, and Ethiopia.
While asthma is more common in affluent countries, it is by no means a restricted problem; the WHO estimate that there are between 15 and 20 million people with asthma in India. In the U.S., urban residents, Hispanics, and African Americans are affected more than the population as a whole. Striking increases in asthma prevalence have been observed in populations migrating from a rural environment to an urban one, or from a third-world country to Westernized one.
Asthma affects approximately 7% of the population of the United States and 5% of people in the United Kingdom. Asthma causes 4,210 deaths per year in the United States. In 2005 in the United States asthma affected more than 22 million people including 6 million children. It accounted for nearly 1/2 million hospitalizations that same year. More boys have asthma than girls, but more women have it than men. Of all children, African Americans and Latinos who live in cities are more at risk for developing asthma. African American children in the U.S. are four times more likely to die of asthma and three times more likely to be hospitalized, compared to their white counterparts. In some Latino neighborhoods, as many as one in three children has been found to have asthma.
In England, an estimated 261,400 people were newly diagnosed with asthma in 2005; 5.7 million people had an asthma diagnosis and were prescribed 32.6 million asthma-related prescriptions.
The frequency of atopic dermatitis, asthma, urticaria and allergic contact dermatitis has been found to be lower in psoriatic
patients.
(WHO) reports that some 10% of the Swiss population suffers from asthma today, compared with just 2% some 25–30 years ago. In the United States specifically data from several national surveys in the United States reveal the age-adjusted prevalence of asthma increased from 7.3 to 8.2 percent during the years 2001 through 2009
. Previous analysis of data from 2001 to 2007 had suggested the prevalence of asthma was stable.
is lower in Puerto Ricans than in African Americans or Mexicans. As with worldwide asthma disparities, differences in asthma prevalence, mortality, and drug response in the US may be explained by differences in genetic, social and environmental risk factors.
Asthma prevalence also differs between populations of the same ethnicity who are born and live in different places. US-born Mexican populations, for example, have higher asthma rates than non-US born Mexican populations that are living in the US.
There is no correlation between asthma and gender in children. More adult women are diagnosed with asthma than adult men, but this does not necessarily mean that more adult women have asthma.
circa 450 BC. During the 1930s–50s, asthma was considered as being one of the 'holy seven' psychosomatic illness
es. Its aetiology
was considered to be psychological, with treatment often based on psychoanalysis and other 'talking cure
s'. As these psychoanalysts interpreted the asthmatic wheeze as the suppressed cry of the child for its mother, so they considered that the treatment of depression was especially important for individuals with asthma. among the first papers in modern medicine, is one that was published in 1873 and this paper tried to explain the pathophysiology
of the disease. And one of the first papers discussing treatment of asthma was released in 1872, the author concluded in his paper that asthma can be cured by rubbing the chest with chloroform liniment
.
Among the first times researchers referred to medical treatment was in 1880, when Dr. J. B. Berkart used IV therapy
to administer doses of a drug called pilocarpin. In 1886, F.H. Bosworth FH suspected a connection between asthma and hay fever
. Epinephrine
was first referred to in the treatment of asthma in 1905, and for acute asthma in 1910.
Chronic (medicine)
A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...
inflammatory disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm
Bronchospasm
Bronchospasm or a bronchial spasm is a sudden constriction of the muscles in the walls of the bronchioles. It is caused by the release of substances from mast cells or basophils under the influence of anaphylatoxins...
. Symptoms include wheezing, coughing, chest tightness, and shortness of breath. Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in 1 second (FEV1
Spirometry
Spirometry is the most common of the pulmonary function tests , measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled...
), and peak expiratory flow rate. Asthma may also be classified as atopic
Atopy
Atopy or atopic syndrome is a predisposition toward developing certain allergic hypersensitivity reactions.Atopy may have a hereditary component, although contact with the allergen must occur before the hypersensitivity reaction can develop ....
(extrinsic) or non-atopic (intrinsic).
It is thought to be caused by a combination of genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
and environmental factors. Treatment of acute symptoms is usually with an inhaled short-acting beta-2 agonist (such as salbutamol
Salbutamol
Salbutamol or albuterol is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. It is marketed as Ventolin among other brand names....
). Symptoms can be prevented by avoiding triggers, such as allergens and irritants
Irritation
Irritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
, and by inhaling corticosteroids. Leukotriene antagonist
Leukotriene antagonist
A leukotriene antagonist is a drug that inhibits leukotrienes, which are fatty compounds produced by the immune system that cause inflammation in asthma and bronchitis, and constrict airways....
s are less effective than corticosteroids and thus less preferred.
Its diagnosis is usually made based on the pattern of symptoms and/or response to therapy over time. The prevalence of asthma has increased significantly since the 1970s. As of 2010, 300 million people were affected worldwide. In 2009 asthma caused 250,000 deaths globally. Despite this, with proper control of asthma with step down therapy, prognosis is generally good.
Classification
Asthma is defined by the Global Initiative for AsthmaGlobal Initiative for Asthma
The Global Initiative for Asthma is a medical guidelines organisation which works with public health officials and health care professionals globally to reduce asthma prevalence, morbidity, and mortality....
as "a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. The chronic inflammation is associated with airway hyperresponsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness and coughing particularly at night or in the early morning. These episodes are usually associated with widespread, but variable airflow obstruction within the lung that is often reversible either spontaneously or with treatment".
| Severity in patients ≥ 12 years of age | Symptom frequency | Night time symptoms | %FEV1 of predicted | FEV1 Variability | Use of short-acting beta2 agonist for symptom control (not for prevention of EIB) |
|---|---|---|---|---|---|
| Intermittent | ≤2 per week | ≤2 per month | ≥80% | <20% | ≤2 days per week |
| Mild persistent | >2 per week but not daily |
3–4 per month | ≥80% | 20–30% | >2 days/week but not daily |
| Moderate persistent | Daily | >1 per week but not nightly | 60–80% | >30% | Daily |
| Severe persistent | Throughout the day | Frequent (often 7×/week) | <60% | >30% | Several times per day |
Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in 1 second (FEV1
Spirometry
Spirometry is the most common of the pulmonary function tests , measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled...
), and peak expiratory flow rate. Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic).
While asthma is classified based on severity, at the moment there is no clear method for classifying different subgroups of asthma beyond this system. Within the classifications described above, although the cases of asthma respond to the same treatment differs, thus it is clear that the cases within a classification have significant differences. Finding ways to identify subgroups that respond well to different types of treatments is a current critical goal of asthma research.
Although asthma is a chronic
Chronic (medicine)
A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...
obstructive
Obstructive lung disease
Obstructive lung disease is a category of respiratory disease characterized by airway obstruction. It is generally characterized by inflamed and easily collapsible airways, obstruction to airflow, and frequent office visits and hospitalizations. Types of obstructive lung disease include; Asthma,...
condition, it is not considered as a part of chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
as this term refers specifically to combinations of disease that are irreversible such as bronchiectasis
Bronchiectasis
Bronchiectasis is a disease state defined by localized, irreversible dilation of part of the bronchial tree caused by destruction of the muscle and elastic tissue. It is classified as an obstructive lung disease, along with emphysema, bronchitis, asthma, and cystic fibrosis...
, chronic bronchitis
Chronic bronchitis
Chronic bronchitis is a chronic inflammation of the bronchi in the lungs. It is generally considered one of the two forms of chronic obstructive pulmonary disease...
, and emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
. Unlike these diseases, the airway obstruction in asthma is usually reversible; however, if left untreated, the chronic inflammation of the lungs during asthma can become irreversible obstruction due to airway remodeling. In contrast to emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
, asthma affects the bronchi, not the alveoli.
Brittle asthma
Brittle asthma is a term used to describe two types of asthma, distinguishable by recurrent, severe attacks. Type 1 brittle asthma refers to disease with wide peak flow variability, despite intense medication. Type 2 brittle asthma describes background well-controlled asthma, with sudden severe exacerbationsIrritation
Irritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...
.
Asthma attack
An acute asthma exacerbation is commonly referred to as an asthma attack. The classic symptoms are shortness of breath, wheezingWheeze
A wheeze is a continuous, coarse, whistling sound produced in the respiratory airways during breathing. For wheezes to occur, some part of the respiratory tree must be narrowed or obstructed, or airflow velocity within the respiratory tree must be heightened...
, and chest tightness. While these are the primary symptoms of asthma, some people present primarily with cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
ing, and in severe cases, air motion may be significantly impaired such that no wheezing is heard.
Signs which occur during an asthma attack include the use of accessory muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s of respiration (sternocleidomastoid and scalene muscles
Scalene muscles
The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the scalenus anterior, scalenus medius, and scalenus posterior.They are innervated by the spinal nerves C4-C6....
of the neck), there may be a paradoxical pulse
Pulsus paradoxus
In medicine, a pulsus paradoxus , also paradoxic pulse or paradoxical pulse, is defined as an exaggeration of the normal variation during the inspiratory phase of respiration, in which the blood pressure declines as one inhales and increases as one exhales...
(a pulse that is weaker during inhalation and stronger during exhalation), and over-inflation of the chest. A blue color
Cyanosis
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...
of the skin and nails may occur from lack of oxygen.
In a mild exacerbation the peak expiratory flow rate (PEFR) is ≥200 L/min or ≥50% of the predicted best. Moderate is defined as between 80 and 200 L/min or 25% and 50% of the predicted best while severe is defined as ≤ 80 L/min or ≤25% of the predicted best.
Insufficient levels of vitamin D are linked with severe asthma attacks.
Status asthmaticus
Status asthmaticus is an acute exacerbation of asthma that does not respond to standard treatments of bronchodilators and steroids. Nonselective beta blockers (such as Timolol) have caused fatal status asthmaticus.Exercise induced
A diagnosis of asthma is common among top athletes. One survey of participants in the 1996 Summer Olympic GamesSummer Olympic Games
The Summer Olympic Games or the Games of the Olympiad are an international multi-sport event, occurring every four years, organized by the International Olympic Committee. Medals are awarded in each event, with gold medals for first place, silver for second and bronze for third, a tradition that...
, in Atlanta, Georgia, U.S., showed that 15% had been diagnosed with asthma, and that 10% were on asthma medication.
There appears to be a relatively high incidence of asthma in sports such as cycling
Cycling
Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, or for sport. Persons engaged in cycling are cyclists or bicyclists...
, mountain biking, and long-distance running
Running
Running is a means of terrestrial locomotion allowing humans and other animals to move rapidly on foot. It is simply defined in athletics terms as a gait in which at regular points during the running cycle both feet are off the ground...
, and a relatively lower incidence in weightlifting and diving. It is unclear how much of these disparities are from the effects of training in the sport.
Exercise induced asthma can be treated with the use of a short-acting beta2 agonist.
Occupational
Asthma as a result of (or worsened by) workplace exposures is a commonly reported occupational respiratory disease. Still most cases of occupational asthma are not reported or are not recognized as such. Estimates by the American Thoracic SocietyAmerican Thoracic Society
American Thoracic Society , established in 1905, is an independently incorporated, international, educational and scientific society, serving its 18,000 members worldwide who are dedicated in respiratory and critical care medicine...
(2004) suggest that 15–23% of new-onset asthma cases in adults are work related. In one study monitoring workplace asthma by occupation, the highest percentage of cases occurred among operators
Operator (profession)
An operator is a professional designation used in various industries, including broadcasting , computing, customer service, physics, and construction. Operators are day-to-day end users of systems, that may or may not be mission-critical, but are typically managed and maintained by technicians or...
, fabricators, and laborers (32.9%), followed by managerial and professional specialists (20.2%), and in technical, sales, and administrative support jobs (19.2%). Most cases were associated with the manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
(41.4%) and services (34.2%) industries. Animal proteins, enzymes, flour
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...
, natural rubber latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...
, and certain reactive chemicals are commonly associated with work-related asthma. When recognized, these hazards can be mitigated, dropping the risk of disease.
Signs and symptoms
Common symptoms of asthma include wheezing, shortness of breath, chest tightness and coughCough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
ing, and use of accessory muscle. Symptoms are often worse at night or in the early morning, or in response to exercise or cold air. Some people with asthma only rarely experience symptoms, usually in response to triggers, whereas other may have marked persistent airflow obstruction.
Gastro-esophageal reflux disease
Gastro-esophageal reflux disease coexists with asthma in 80% of people with asthma, with similar symptoms. Various theories say that asthma could facilitate GERD and/or viceversa. The first case could be due to the effect of change in thoracic pressures, use of antiasthma drugs, could facilitate the passage of the gastric content back into the oesophagus by increasing abdominal pressure or decreasing the lower esophageal sphincter. The second by promoting bronchoconstriction and irritation by chronic acid aspiration, vagally mediated reflexes and others factors that increase bronchial responsiveness and irritation.Sleep disorders
Due to altered anatomy of the respiratory tract: increased upper airway adipose deposition, altered pharynx skeletal morphology, and extension of the pharyngeal airway; leading to upper airway collapse.Causes
Asthma is caused by environmental and genetic factors. These factors influence how severe asthma is and how well it responds to medication. The interaction is complex and not fully understood.Studying the prevalence of asthma and related diseases such as eczema
Eczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
and hay fever
Rhinitis
Rhinitis , commonly known as a stuffy nose, is the medical term describing irritation and inflammation of some internal areas of the nose. The primary symptom of rhinitis is nasal dripping. It is caused by chronic or acute inflammation of the mucous membrane of the nose due to viruses, bacteria or...
have yielded important clues about some key risk factors. The strongest risk factor for developing asthma is a history of atopic disease
Atopy
Atopy or atopic syndrome is a predisposition toward developing certain allergic hypersensitivity reactions.Atopy may have a hereditary component, although contact with the allergen must occur before the hypersensitivity reaction can develop ....
; this increases one's risk of hay fever by up to 5× and the risk
Risk
Risk is the potential that a chosen action or activity will lead to a loss . The notion implies that a choice having an influence on the outcome exists . Potential losses themselves may also be called "risks"...
of asthma by 3–4×. In children between the ages of 3–14, a positive skin test for allergies
Allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...
and an increase in immunoglobulin E
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
increases the chance of having asthma. In adults, the more allergens one reacts positively to in a skin test, the higher the odds of having asthma.
Because much allergic asthma is associated with sensitivity to indoor allergens and because Western styles of housing favor greater exposure to indoor allergens, much attention has focused on increased exposure to these allergens in infancy and early childhood as a primary cause of the rise in asthma. Primary prevention studies aimed at the aggressive reduction of airborne allergens in a home with infants have shown mixed findings. Strict reduction of dust mite allergens, for example, reduces the risk of allergic sensitization to dust mites, and modestly reduces the risk of developing asthma up until the age of 8 years old. However, studies also showed that the effects of exposure to cat and dog allergens worked in the converse fashion; exposure during the first year of life was found to reduce the risk of allergic sensitization and of developing asthma later in life.
The inconsistency of this data has inspired research into other facets of Western society and their impact upon the prevalence of asthma. One subject that appears to show a strong correlation is the development of asthma and obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
. In the United Kingdom and United States, the rise in asthma prevalence has echoed an almost epidemic rise in the prevalence of obesity. In Taiwan, symptoms of allergies and airway hyper-reactivity increased in correlation with each 20% increase in body-mass index. Several factors associated with obesity may play a role in the pathogenesis of asthma, including decreased respiratory function due to a buildup of adipose tissue (fat) and the fact that adipose tissue leads to a pro-inflammatory state, which has been associated with non-eosinophilic asthma.
Asthma has been associated with Churg–Strauss syndrome, and individuals with immunologically mediated urticaria may also experience systemic symptoms with generalized urticaria, rhino-conjunctivitis, orolaryngeal and gastrointestinal symptoms, asthma, and, at worst, anaphylaxis. Additionally, adult-onset asthma has been associated with periocular xanthogranulomas.
Environmental
Many environmental risk factorRisk factor
In epidemiology, a risk factor is a variable associated with an increased risk of disease or infection. Sometimes, determinant is also used, being a variable associated with either increased or decreased risk.-Correlation vs causation:...
s have been associated with asthma development and morbidity in children. Recent studies show a relationship between exposure to air pollutants (e.g. from traffic) and childhood asthma. This research finds that both the occurrence of the disease and exacerbation of childhood asthma are affected by outdoor air pollutants. High levels of endotoxin
Endotoxin
Endotoxins are toxins associated with some Gram-negative bacteria. An "endotoxin" is a toxin that is a structural molecule of the bacteria that is recognized by the immune system.-Gram negative:...
exposure may contribute to asthma risk.
Viral respiratory infections are not only one of the leading triggers of an exacerbation but may increase one's risk of developing asthma especially in young children.
Respiratory infections such as rhinovirus
Rhinovirus
Human rhinoviruses are the most common viral infective agents in humans and are the predominant cause of the common cold. Rhinovirus infection proliferates in temperatures between 33–35 °C , and this may be why it occurs primarily in the nose...
, Chlamydia pneumoniae and Bordetella pertussis
Bordetella pertussis
Bordetella pertussis is a Gram-negative, aerobic coccobacillus of the genus Bordetella, and the causative agent of pertussis or whooping cough. Unlike B. bronchiseptica, B. pertussis is non-motile. Its virulence factors include pertussis toxin, filamentous hæmagglutinin, pertactin, fimbria, and...
are correlated with asthma exacerbations.
Psychological stress has long been suspected of being an asthma trigger, but only in recent decades has convincing scientific evidence substantiated this hypothesis. Rather than stress directly causing the asthma symptoms, it is thought that stress modulates the immune system to increase the magnitude of the airway inflammatory response to allergens and irritants.
Beta blocker
Beta blocker
Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...
medications such as metoprolol may trigger asthma in those who are susceptible.
Tobacco
Maternal tobacco smoking during pregnancy and after delivery is associated with a greater risk of asthma-like symptoms, wheezing, and respiratory infections during childhood. Low air qualityAir Quality Index
Air quality is defined as a measure of the condition of air relative to the requirements of one or more biotic species or to any human need or purpose. Air quality indices are numbers used by government agencies to characterize the quality of the air at a given location...
, from traffic pollution or high ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
levels, has been repeatedly associated with increased asthma morbidity and has a suggested association with asthma development that needs further research.
Hygiene hypothesis
AntibioticAntibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
use early in life has been linked to development of asthma in several examples; it is thought that antibiotics make children who are predisposed to atopic immune responses susceptible to development of asthma because they modify gut flora
Gut flora
Gut flora consists of microorganisms that live in the digestive tracts of animals and is the largest reservoir of human flora. In this context, gut is synonymous with intestinal, and flora with microbiota and microflora....
, and thus the immune system (as described by the hygiene hypothesis). The hygiene hypothesis
Hygiene hypothesis
In medicine, the Hygiene Hypothesis states that a lack of early childhood exposure to infectious agents, symbiotic microorganisms , and parasites increases susceptibility to allergic diseases by suppressing natural development of the immune system...
(see below) is a hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
about the cause of asthma and other allergic disease, and is supported by epidemiologic data for asthma. All of these things may negatively affect exposure to beneficial bacteria and other immune system modulators that are important during development, and thus may cause an increased risk for asthma and allergy.
Caesarean section
Caesarean section
A Caesarean section, is a surgical procedure in which one or more incisions are made through a mother's abdomen and uterus to deliver one or more babies, or, rarely, to remove a dead fetus...
s have been associated with asthma, possibly because of modifications to the immune system (as described by the hygiene hypothesis).
Volatile organic compounds
Observational studies have found that indoor exposure to volatile organic compounds (VOCs) may be one of the triggers of asthma, however experimental studies have not confirmed these observations. Even VOC exposure at low levels has been associated with an increase in the risk of pediatric asthma. Because there are so many VOCs in the air, measuring total VOC concentrations in the indoor environment may not represent the exposure of individual compounds. Exposure to VOCs is associated with an increase in the IL-4 producing Th2 cells and a reduction in IFN-γ producing Th1 cells. Thus the mechanism of action of VOC exposure may be allergic sensitization mediated by a Th2 cell phenotype. Different individual variations in discomfort, from no response to excessive response, were seen in one of the studies. These variations may be due to the development of tolerance during exposure. Another study has concluded that formaldehyde may cause asthma-like symptoms. Low VOC emitting materials should be used while doing repairs or renovations which decreases the symptoms related to asthma caused by VOCs and formaldehydeFormaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
. In another study "the indoor concentration of aliphatic compounds (C8-C11), butanols, and 2,2,4-trimethyl 1,3-pentanediol diisobutyrate (TXIB) was significantly elevated in newly painted dwellings. The total indoor VOC was about 100 micrograms/m3 higher in dwellings painted in the last year". The author concluded that some VOCs may cause inflammatory reactions in the airways and may be the reason for asthmatic symptoms.
Phthalates
There is a significant association between asthma-like symptoms (wheezing) among preschool children and the concentration of DEHP (phthalates) in indoor environment. DEHP (di-ethylhexyl phthalate) is a plasticizer that is commonly used in building material. The hydrolysis product of DEHP (di-ethylhexyl phthalate) is MEHP (Mono-ethylhexyl phthalate) which mimics the prostaglandins and thromboxanes in the airway leading to symptoms related to asthma. Another mechanism that has been studied regarding phthalates causation of asthma is that high phthalates level can "modulate the murine immune response to a coallergen". Asthma can develop in the adults who come in contact with heated PVC fumes. Two main type of phthalates, namely n-butyl benzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP), have been associated between the concentration of polyvinyl chloride (PVC) used as flooring and the dust concentrations. Water leakage were associated more with BBzP, and buildings construction were associated with high concentrations of DEHP. Asthma has been shown to have a relationship with plaster wall materials and wall-to wall carpeting. The onset of asthma was also related to the floor–leveling plaster at home. Therefore, it is important to understand the health aspect of these materials in the indoor surfaces.Nitrogen Dioxide
Gas cooking stoves have emissions of Carbon monoxideCarbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
, , , NO
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
, aldehydes, RSP, and other VOC’s. The exposure concentration of is 18–35 ppbv, These numbers are significantly high and can had adverse effects on asthma. The inhalation of has an increased risk of respiratory symptoms and can change the lung function in children. According to the United States Environmental Protection Agency it is significantly important to use the exhaust fan when cooking with gas stoves to eliminate as many compounds from the air as possible.
The effects of on the respiratory system can be detrimental to one's health in a range of ways. In patients who are already asthmatic, lung function can decrease but non-asthmatic patients see no effects with concentrations under 1000 ppb. This article states that there is a dose-response relationship between and lung function; significant decrease in lung function at higher levels. The effects of from gas stoves, according to this study, are inconsistent and this is because the actual amount of was not measured. However, in the indoor environment, with the use of gas stoves for cooking, children had a 20% increase of asthmatic symptoms.
Genetic
Over 100 geneGene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s have been associated with asthma in at least one genetic association
Genetic association
Genetic association is the occurrence, more often than can be readily explained by chance, of two or more traits in a population of individuals, of which at least one trait is known to be genetic....
study. However, such studies must be repeated to ensure the findings are not due to chance. Through the end of 2005, 25 genes had been associated with asthma in six or more separate populations:
- GSTM1Glutathione S-transferase Mu 1Glutathione S-transferase Mu 1 is a human glutathione S-transferase.-Further reading:...
- IL10Interleukin 10Interleukin-10 , also known as human cytokine synthesis inhibitory factor , is an anti-inflammatory cytokine. In humans IL-10 is encoded by the IL10 gene....
- CTLA-4CTLA-4CTLA4 also known as CD152 is a protein that plays an important regulatory role in the immune system...
- SPINK5SPINK5Lympho-epithelial Kazal-type-related inhibitor also known as serine protease inhibitor Kazal-type 5 is a protein that in humans is encoded by the SPINK5 gene.- Structure and function :...
- LTC4SLeukotriene C4 synthaseLeukotriene C4 synthase is an enzyme that in humans is encoded by the LTC4S gene.The protein encoded by this gene, LTC4S is an enzyme that converts leukotriene A4 and glutathione to create leukotriene C4. This is a member of MAPEG family of transmembrane proteins...
- LTALymphotoxin alphaLymphotoxin-alpha is a protein that in humans is encoded by the LTA gene.- Function :Lymphotoxin alpha, a member of the tumor necrosis factor family, is a cytokine produced by lymphocytes. LTA is highly inducible, secreted, and exists as homotrimeric molecule. LTA forms heterotrimers with...
- GRPA
- NOD1NOD1Nucleotide-binding oligomerization domain-containing protein 1 is a protein receptor that in humans is encoded by the NOD1 gene. It recognizes bacterial molecules and stimulates an immune reaction....
- CC16
- GSTP1GSTP1Glutathione S-transferase P is an enzyme that in humans is encoded by the GSTP1 gene.-Interactions:GSTP1 has been shown to interact with Fanconi anemia, complementation group C and MAPK8.-Further reading:...
- STAT6STAT6STAT6 is a human gene. The protein encoded by this gene is a member of the STAT family of transcription factors.In response to cytokines and growth factors, STAT family members are phosphorylated by the receptor associated kinases, and then form homo- or heterodimers that translocate to the cell...
- NOS1NOS1Nitric oxide synthase 1 , also known as NOS1, is an enzyme that in humans is encoded by the NOS1 gene.- Function :Nitric oxide is a messenger molecule with diverse functions throughout the body...
- CCL5
- TBXA2RThromboxane receptorThe thromboxane receptor is a protein on the surface of cells in the endothelium of blood vessels and in the placenta which interacts with the eicosanoid lipid thromboxane. It is a G-protein coupled receptor coupled to the G protein Gq.-Gene:...
- TGFB1
- IL4Interleukin 4Interleukin-4, abbreviated IL-4, is a cytokine that induces differentiation of naive helper T cells to Th2 cells. Upon activation by IL-4, Th2 cells subsequently produce additional IL-4. The cell that initially produces IL-4, thus inducing Th0 differentiation, has not been identified, but recent...
- IL13Interleukin 13Interleukin 13 is a protein that in humans is encoded by the IL13 gene. IL-13 is cytokine secreted by many cell types, but especially T helper type 2 cells, that is a mediator of allergic inflammation and disease.-Functions:...
- CD14CD14Cluster of differentiation 14 also known as CD14 is a human gene.The protein encoded by this gene is a component of the innate immune system. CD14 exists in two forms. Either it is anchored into the membrane by a glycosylphosphatidylinositol tail or it appears in a soluble form...
- ADRB2Beta-2 adrenergic receptorThe beta-2 adrenergic receptor , also known as ADRB2, is a beta-adrenergic receptor, and also denotes the human gene encoding it.-Gene:The gene is intronless...
(β-2 adrenergic receptor) - HLA-DRB1HLA-DRB1HLA class II histocompatibility antigen, DRB1-9 beta chain is a protein that in humans is encoded by the HLA-DRB1 gene. DRB1 encodes the most prevalent beta subunit of HLA-DR.- Function :...
- HLA-DQB1HLA-DQB1Major histocompatibility complex, class II, DQ beta 1, also known as HLA-DQB1, is a human gene and also denotes the genetic locus that contains this gene...
- TNFTumor necrosis factorsTumor necrosis factors refers to a group of cytokines family that can cause cell death . The first two members of the family to be identified were:...
- FCER1B
- IL4RInterleukin-4 receptorInterleukin 4 receptor is a type I cytokine receptor. IL4R is its human gene.-Interactions:Interleukin-4 receptor has been shown to interact with SHC1.-Further reading:-External links:...
- ADAM33ADAM33Disintegrin and metalloproteinase domain-containing protein 33 is an enzyme that in humans is encoded by the ADAM33 gene.-External links:* The MEROPS online database for peptidases and their inhibitors:...
Many of these genes are related to the immune system or to modulating inflammation. However, even among this list of highly replicated genes associated with asthma, the results have not been consistent among all of the populations that have been tested. This indicates that these genes are not associated with asthma under every condition, and that researchers need to do further investigation to figure out the complex interactions that cause asthma. One theory is that asthma is a collection of several diseases, and that genes might have a role in only subsets of asthma. For example, one group of genetic differences (single nucleotide polymorphism
Single nucleotide polymorphism
A single-nucleotide polymorphism is a DNA sequence variation occurring when a single nucleotide — A, T, C or G — in the genome differs between members of a biological species or paired chromosomes in an individual...
s in 17q21
Chromosome 17 (human)
125px|rightChromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 17 spans more than 81 million base pairs and represents between 2.5 and 3 % of the total DNA in cells.Identifying genes on each chromosome is an active area of...
) was associated with asthma that develops in childhood.
Gene–environment interactions
| Endotoxin levels | CC genotype | TT genotype |
|---|---|---|
| High exposure | Low risk | High risk |
| Low exposure | High risk | Low risk |
Research suggests that some genetic variants may only cause asthma when they are combined with specific environmental exposures, and otherwise may not be risk factors for asthma.
The genetic trait, CD14 single nucleotide polymorphism
Single nucleotide polymorphism
A single-nucleotide polymorphism is a DNA sequence variation occurring when a single nucleotide — A, T, C or G — in the genome differs between members of a biological species or paired chromosomes in an individual...
(SNP) C-159T and exposure to endotoxin
Endotoxin
Endotoxins are toxins associated with some Gram-negative bacteria. An "endotoxin" is a toxin that is a structural molecule of the bacteria that is recognized by the immune system.-Gram negative:...
(a bacterial product) are a well-replicated example of a gene-environment interaction that is associated with asthma. Endotoxin exposure varies from person to person and can come from several environmental sources, including environmental tobacco smoke, dogs, and farms. Researchers have found that risk for asthma changes based on a person's genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
at CD14 C-159T and level of endotoxin exposure.
Exacerbation
Some individuals will have stable asthma for weeks or months and then suddenly develop an episode of acute asthma. Different asthmatic individuals react differently to various factors. However, most individuals can develop severe exacerbation of asthma from several triggering agents.Home factors that can lead to exacerbation include dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
, house mites
House dust mite
The house dust mite is a cosmopolitan guest in human habitation. Dust mites feed on organic detritus such as flakes of shed human skin and flourish in the stable environment of dwellings. House dust mites are a common cause of asthma and allergic symptoms worldwide...
, animal dander
Dander
Dander is an informal term for a material shed from the body of various animals, similar to dandruff. It may contain scales of dried skin and hair, or feathers. It is a cause of allergies in humans....
(especially cat and dog hair), cockroach allergen
Allergen
An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....
s and mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...
s at any given home. Perfume
Perfume
Perfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...
s are a common cause of acute attacks in females and children. Both virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
and bacterial infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s of the upper respiratory tract infection can worsen asthma.
Hygiene hypothesis
One theory for the cause of the increase in asthma prevalence worldwide is the "hygiene hypothesisHygiene hypothesis
In medicine, the Hygiene Hypothesis states that a lack of early childhood exposure to infectious agents, symbiotic microorganisms , and parasites increases susceptibility to allergic diseases by suppressing natural development of the immune system...
" —that the rise in the prevalence of allergies and asthma is a direct and unintended result of reduced exposure to a wide variety of different bacteria and virus types in modern societies, or modern hygienic practices preventing childhood infections. Children living in less hygienic environments (East Germany vs. West Germany, families with many children, day care environments) tend to have lower incidences of asthma and allergic diseases. This seems to run counter to the logic that viruses are often causative agents in exacerbation of asthma. Additionally, other studies have shown that viral infections of the lower airway may in some cases induce asthma, as a history of bronchiolitis
Bronchiolitis
Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It usually occurs in children less than two years of age and presents with coughing, wheezing, and shortness of breath. This inflammation is usually caused by viruses...
or croup
Croup
Croup is a respiratory condition that is usually triggered by an acute viral infection of the upper airway. The infection leads to swelling inside the throat, which interferes with normal breathing and produces the classical symptoms of a "barking" cough, stridor, and hoarseness...
in early childhood is a predictor of asthma risk in later life. Studies which show that upper respiratory tract infections are protective against asthma risk also tend to show that lower respiratory tract infections conversely tend to increase the risk of asthma.
Socioeconomic factors
The incidence of asthma is highest among low-income populations worldwide. Asthma deaths are most common in low and middle income countries, and in the Western world, it is found in those low-income neighborhoods whose populations consist of large percentages of ethnic minorities. Additionally, asthma has been strongly associated with the presence of cockroachCockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
es in living quarters; these insects are more likely to be found in those same neighborhoods.
Most likely due to income and geography, the incidence of and treatment quality for asthma varies among different racial groups. The prevalence of "severe persistent" asthma is also greater in low-income communities than those with better access to treatment.
Diagnosis
| Near-fatal asthma | High PaCO2 Arterial blood gas An arterial blood gas is a blood test that is performed using blood from an artery. It involves puncturing an artery with a thin needle and syringe and drawing a small volume of blood. The most common puncture site is the radial artery at the wrist, but sometimes the femoral artery in the groin or... and/or requiring mechanical ventilation |
|
|---|---|---|
| Life threatening asthma | Any one of the following in a person with severe asthma:- | |
| Clinical signs | Measurements | |
| Altered level of consciousness | Peak flow < 33% | |
| Exhaustion | Oxygen saturation Oxygen saturation Oxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.It has particular significance in medicine and... < 92% |
|
| Arrhythmia | PaO2 Arterial blood gas An arterial blood gas is a blood test that is performed using blood from an artery. It involves puncturing an artery with a thin needle and syringe and drawing a small volume of blood. The most common puncture site is the radial artery at the wrist, but sometimes the femoral artery in the groin or... < 8 kPa |
|
| Low blood pressure Blood pressure Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies... |
"Normal" PaCO2 | |
| Cyanosis Cyanosis Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is... |
||
| Silent chest | ||
| Poor respiratory effort | ||
| Acute severe asthma | Any one of:- | |
| Peak flow 33–50% | ||
| Respiratory rate ≥ 25 breaths per minute | ||
| Heart rate ≥ 110 beats per minute | ||
| Unable to complete sentences in one breath | ||
| Moderate asthma exacerbation | Worsening symptoms | |
| Peak flow 80–50% best or predicted | ||
| No features of acute severe asthma | ||
There is currently not a precise physiologic, immunologic, or histologic test for diagnosing asthma. The diagnosis is usually made based on the pattern of symptoms (airways obstruction and hyperresponsiveness) and/or response to therapy (partial or complete reversibility) over time.
The British Thoracic Society
British Thoracic Society
The British Thoracic Society was formed in 1982 by the amalgamation of the British Thoracic Association and the Thoracic Society. It is a registered charity and a company limited by guarantee.-Function:...
determines a diagnosis of asthma using a ‘response to therapy’ approach. If the patient responds to treatment, then this is considered to be a confirmation of the diagnosis of asthma. The response measured is the reversibility of airway obstruction after treatment. Airflow in the airways is measured with a peak flow meter
Peak flow meter
The peak expiratory flow , also called peak expiratory flow rate is a person's maximum speed of expiration, as measured with a peak flow meter, a small, hand-held device used to monitor a person's ability to breathe out air...
or spirometer
Spirometer
A spirometer is an apparatus for measuring the volume of air inspired and expired by the lungs. It is a precision differential pressure transducer for the measurements of respiration flow rates. The spirometer records the amount of air and the rate of air that is breathed in and out over a...
, and the following diagnostic criteria are used by the British Thoracic Society
British Thoracic Society
The British Thoracic Society was formed in 1982 by the amalgamation of the British Thoracic Association and the Thoracic Society. It is a registered charity and a company limited by guarantee.-Function:...
:
- ≥20% difference on at least three days in a week for at least two weeks;
- ≥20% improvement of peak flow following treatment, for example:
- 10 minutes of inhaled β-agonist (e.g., salbutamolSalbutamolSalbutamol or albuterol is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. It is marketed as Ventolin among other brand names....
); - six weeks of inhaled corticosteroidCorticosteroidCorticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
(e.g., beclometasoneBeclometasone dipropionateBeclometasone dipropionate or beclomethasone dipropionate , also referred to as beclometasone , is a potent glucocorticoid steroid. In the form of an inhaler , a wide number of brands of which are available, it is used for the prophylaxis of asthma. As a nasal spray Beclometasone dipropionate (INN...
); - 14 days of 30 mg prednisolonePrednisolonePrednisolone is the active metabolite of prednisone, which is also used as a drug.-Uses:Prednisolone is a corticosteroid drug with predominant glucocorticoid and low mineralocorticoid activity, making it useful for the treatment of a wide range of inflammatory and auto-immune conditions such as...
.
- 10 minutes of inhaled β-agonist (e.g., salbutamol
- ≥20% decrease in peak flow following exposure to a trigger (e.g., exercise).
In contrast, the US National Asthma Education and Prevention Program (NAEPP) uses a ‘symptom patterns’ approach. Their guidelines for the diagnosis and management of asthma state that a diagnosis of asthma begins by assessing if any of the following list of indicators is present. While the indicators are not sufficient to support a diagnosis of asthma, the presence of multiple key indicators increases the probability of a diagnosis of asthma. Spirometry
Spirometry
Spirometry is the most common of the pulmonary function tests , measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled...
is needed to establish a diagnosis of asthma.
- Wheezing—high-pitched whistling sounds when breathing out—especially in children. (Lack of wheezing and a normal chest examination do not exclude asthma.)
- history of any of the following:
- Cough, worse particularly at night
- Recurrent wheeze
- Recurrent difficulty in breathing
- Recurrent chest tightness
- Symptoms occur or worsen in the presence of:
- Exercise
- Viral infection
- Animals with fur or hair
- House-dust mites (in mattresses, pillows, upholstered furniture, carpets)
- Mold
- Smoke (tobacco, wood)
- Pollen
- Changes in weather
- Strong emotional expression (laughing or crying hard)
- Airborne chemicals or dusts
- Menstrual cycles
- Symptoms occur or worsen at night, awakening the patient
The latest guidelines from the U.S. National Asthma Education and Prevention Program (NAEPP) recommend spirometry
Spirometry
Spirometry is the most common of the pulmonary function tests , measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled...
at the time of initial diagnosis, after treatment is initiated and symptoms are stabilized, whenever control of symptoms deteriorates, and every 1 or 2 years on a regular basis. The NAEPP guidelines do not recommend testing peak expiratory flow as a regular screening method because it is more variable than spirometry. However, testing peak flow at rest (or baseline) and after exercise can be helpful, especially in young patients who may experience only exercise-induced asthma
Exercise-induced asthma
Exercise-induced asthma, or E.I.A., is a medical condition characterized by shortness of breath induced by sustained aerobic exercise. It shares many features with other types of asthma, and responds to some typical asthma medications, but does not appear to be caused by the same inflammatory...
. It may also be useful for daily self-monitoring and for checking the effects of new medications. Peak flow readings can be charted together with a record of symptoms or use peak flow charting software. This allows patients to track their peak flow readings and pass information back to their doctor or respiratory therapist.
Differential diagnosis
Differential diagnoses include:- Infants and Children
- Upper airway diseases
- Allergic rhinitisAllergic rhinitisAllergic rhinitis, also known as pollenosis or hay fever, is an allergic inflammation of the nasal airways.It occurs when an allergen, such as pollen, dust or animal dander is inhaled by an individual with a sensitized immune system...
and allergic sinusitisSinusitisSinusitis is inflammation of the paranasal sinuses, which may be due to infection, allergy, or autoimmune issues. Most cases are due to a viral infection and resolve over the course of 10 days...
- Allergic rhinitis
- Obstructions involving large airways
- Foreign body in trachea or bronchus
- Vocal cord dysfunction
- Vascular ringVascular ringA vascular ring is a congenital defect in which there is an abnormal formation of the aorta and/or its surrounding blood vessels. The trachea and esophagus are completely encircled and sometimes compressed by a "ring" formed by these vessels, which can lead to breathing and digestive...
s or laryngeal webs - Laryngotracheomalacia, tracheal stenosisTracheal stenosisLaryngotracheal stenosis refers to abnormal narrowing of the central air passageways. This can occur at the level of the larynx, trachea, carina or main bronchi...
, or bronchostenosis - Enlarged lymph nodes or tumor
- Obstructions involving small airways
- Viral bronchiolitis or obliterative bronchiolitis
- Cystic fibrosisCystic fibrosisCystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...
- Bronchopulmonary dysplasiaBronchopulmonary dysplasiaBronchopulmonary dysplasia is a chronic lung disorder that is most common among children who were born prematurely, with low birthweights and who received prolonged mechanical ventilation to treat respiratory distress syndrome...
- Heart diseaseHeart diseaseHeart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...
- Other causes
- Recurrent cough not due to asthma
- Aspiration from swallowing mechanism dysfunction or gastroesophageal reflux
- Medication induced
- Upper airway diseases
- Adults
- COPD (e.g., chronic bronchitis or emphysema)
- Congestive heart failureCongestive heart failureHeart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
- Pulmonary embolismPulmonary embolismPulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
- Mechanical obstruction of the airways (benign and malignant tumors)
- Pulmonary infiltration with eosinophilia
- Cough secondary to drugs (e.g., angiotensin-converting enzyme (ACE) inhibitors)
- Vocal cord dysfunction
Before diagnosing asthma, alternative possibilities
Differential diagnosis
A differential diagnosis is a systematic diagnostic method used to identify the presence of an entity where multiple alternatives are possible , and may also refer to any of the included candidate alternatives A differential diagnosis (sometimes abbreviated DDx, ddx, DD, D/Dx, or ΔΔ) is a...
should be considered such as the use of known bronchoconstrictors (substances that cause narrowing of the airways, e.g. certain anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....
agents or beta-blockers
Beta blocker
Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...
). Among elderly people, the presenting symptom may be fatigue, cough, or difficulty breathing, all of which may be erroneously attributed to Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
(COPD), congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
, or simple aging.
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary diseaseChronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
can coexist with asthma and can occur as a complication of chronic asthma. After the age of 65 most people with obstructive airway disease will have asthma and COPD. In this setting, COPD can be differentiated by increased airway neutrophils, abnormally increased wall thickness, and increased smooth muscle in the bronchi. However, this level of investigation is not performed due to COPD and asthma sharing similar principles of management: corticosteroids, long acting beta agonists, and smoking cessation. It closely resembles asthma in symptoms, is correlated with more exposure to cigarette smoke, an older age, less symptom reversibility after bronchodilator administration (as measured by spirometry
Spirometry
Spirometry is the most common of the pulmonary function tests , measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled...
), and decreased likelihood of family history of atopy
Atopy
Atopy or atopic syndrome is a predisposition toward developing certain allergic hypersensitivity reactions.Atopy may have a hereditary component, although contact with the allergen must occur before the hypersensitivity reaction can develop ....
.
Others
The term "atopy" was coined to describe this triad of atopic eczema, allergic rhinitisAllergic rhinitis
Allergic rhinitis, also known as pollenosis or hay fever, is an allergic inflammation of the nasal airways.It occurs when an allergen, such as pollen, dust or animal dander is inhaled by an individual with a sensitized immune system...
and asthma.
Pulmonary aspiration
Pulmonary aspiration
Pulmonary aspiration is the entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract...
, whether direct due to dysphagia
Dysphagia
Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia....
(swallowing disorder) or indirect (due to acid reflux), can show similar symptoms to asthma. However, with aspiration, fevers might also indicate aspiration pneumonia
Aspiration pneumonia
Aspiration pneumonia is bronchopneumonia that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents...
. Direct aspiration (dysphagia) can be diagnosed by performing a modified barium swallow
Barium swallow
A barium swallow is a medical imaging procedure used to examine the upper GI tract, which includes the esophagus and, to a lesser extent, the stomach.-Principle:...
test. If the aspiration is indirect (from acid reflux), then treatment is directed at this is indicated.
Prevention
The evidence for the effectiveness of measures to prevent the development of asthma is weak. Ones which show some promise include limiting smoke exposure both in uteroIn utero
In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...
and after delivery, breastfeeding
Breastfeeding
Breastfeeding is the feeding of an infant or young child with breast milk directly from female human breasts rather than from a baby bottle or other container. Babies have a sucking reflex that enables them to suck and swallow milk. It is recommended that mothers breastfeed for six months or...
, increased exposure to respiratory infection per the hygiene hypothesis
Hygiene hypothesis
In medicine, the Hygiene Hypothesis states that a lack of early childhood exposure to infectious agents, symbiotic microorganisms , and parasites increases susceptibility to allergic diseases by suppressing natural development of the immune system...
(such as in those who attend daycare or are from large families).
Management
A specific, customized plan for proactively monitoring and managing symptoms should be created. Someone who has asthma should understand the importance of reducing exposure to allergens, testing to assess the severity of symptoms, and the usage of medications. The treatment plan should be written down and adjusted according to changes in symptoms.The most effective treatment for asthma is identifying triggers, such as cigarette smoke
Health effects of tobacco smoking
The health effects of tobacco are the circumstances, mechanisms, and factors of tobacco consumption on human health. Epidemiological research has been focused primarily on cigarette tobacco smoking, which has been studied more extensively than any other form of consumption.Tobacco is the single...
, pets, or aspirin
Aspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
, and eliminating exposure to them. If trigger avoidance is insufficient, medical treatment is recommended. Medical treatments used depend on the severity of illness and the frequency of symptoms. Specific medications for asthma are broadly classified into fast-acting and long-acting categories.
Bronchodilators are recommended for short-term relief of symptoms. In those with occasional attacks, no other medication is needed. If mild persistent disease is present (more than two attacks a week), low-dose inhaled glucocorticoids or alternatively, an oral leukotriene antagonist
Leukotriene antagonist
A leukotriene antagonist is a drug that inhibits leukotrienes, which are fatty compounds produced by the immune system that cause inflammation in asthma and bronchitis, and constrict airways....
or a mast cell stabilizer
Mast cell stabilizer
Mast cell stabilizers are cromone medications used to prevent or control certain allergic disorders. They block a calcium channel essential for mast cell degranulation, stabilizing the cell and thereby preventing the release of histamine and related mediators. One suspected pharmacodynamic...
is recommended. For those who suffer daily attacks, a higher dose of inhaled glucocorticoid is used. In a severe asthma exacerbation, oral glucocorticoids are added to these treatments.
Lifestyle modification
Avoidance of triggers is a key component of improving control and preventing attacks. The most common triggers include allergenAllergen
An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....
s, smoke (tobacco and other), air pollution, non selective beta-blockers, and sulfite-containing foods.
Cigarette smoking and second hand smoke (passive smoke) in regard to people with asthma causes problems in effectiveness of management medications such as steroid/corticosteroid therapies.
Medications
Medications used to treat asthma are divided into two general classes: quick-relief medications used to treat acute symptoms; and long-term control medications used to prevent further exacerbation.Fast acting
- Short acting beta2-adrenoceptor agonists (SABA), such as salbutamolSalbutamolSalbutamol or albuterol is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. It is marketed as Ventolin among other brand names....
(albuterol USANUnited States Adopted NameUnited States Adopted Names are unique nonproprietary names assigned to pharmaceuticals marketed in the United States. Each name is assigned by the USAN Council, which is co-sponsored by the American Medical Association , the United States Pharmacopeial Convention , and the American Pharmacists...
) are the first line treatment for asthma symptoms. - AnticholinergicAnticholinergicAn anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....
medications, such as ipratropium bromideIpratropiumIpratropium bromide is an anticholinergic drug used for the treatment of chronic obstructive pulmonary disease and acute asthma. It blocks the muscarinic acetylcholine receptors in the smooth muscles of the bronchi in the lungs, opening the bronchi...
, provide additional benefit when used in combination with SABA in those with moderate or severe symptoms. Anticholinergic bronchodilators can also be used if a person cannot tolerate a SABA. - Older, less selective adrenergic agonistsAdrenergic receptorThe adrenergic receptors are a class of metabotropic G protein-coupled receptors that are targets of the catecholamines, especially noradrenaline and adrenaline ....
, such as inhaled epinephrineEpinephrineEpinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
, have similar efficacy to SABAs. They are however not recommended due to concerns regarding excessive cardiac stimulation.
Long term control
- GlucocorticoidGlucocorticoidGlucocorticoids are a class of steroid hormones that bind to the glucocorticoid receptor , which is present in almost every vertebrate animal cell...
s are the most effective treatment available for long term control. Inhaled forms are usually used except in the case of severe persistent disease, in which oral steroids may be needed. Inhaled formulations may be used once or twice daily, depending on the severity of symptoms.
- Long acting beta-adrenoceptor agonistLong acting beta-adrenoceptor agonistLong-acting beta-adrenoceptor agonists are usually prescribed for moderate to severe persistent asthma patients or patients with chronic obstructive pulmonary disease...
s (LABA) have at least a 12-hour effect. They are however not to be used without a steroid due to an increased risk of severe symptoms. In December 2008, members of the FDA's drug-safety office recommended withdrawing approval for these medications in children. Discussion is ongoing about their use in adults. - Leukotriene antagonistLeukotriene antagonistA leukotriene antagonist is a drug that inhibits leukotrienes, which are fatty compounds produced by the immune system that cause inflammation in asthma and bronchitis, and constrict airways....
s (such as zafirlukastZafirlukastZafirlukast is an oral leukotriene receptor antagonist for the maintenance treatment of asthma, often used in conjunction with an inhaled steroid and/or long-acting bronchodilator. It is available as a tablet and is usually dosed twice daily. Another leukotriene receptor antagonist is montelukast...
) are an alternative to inhaled glucocorticoids, but are not preferred. They may also be used in addition to inhaled glucocorticoids but in this role are second line to LABA. - Mast cell stabilizerMast cell stabilizerMast cell stabilizers are cromone medications used to prevent or control certain allergic disorders. They block a calcium channel essential for mast cell degranulation, stabilizing the cell and thereby preventing the release of histamine and related mediators. One suspected pharmacodynamic...
s (such as cromolyn sodium) are another non-preferred alternative to glucocorticoids.
Delivery methods
Medications are typically provided as metered-dose inhalers (MDIs) in combination with an asthma spacer
Asthma spacer
An asthma spacer is an add-on device used to increase the ease of administering aerosolized medication from a "metered-dose inhaler" . The spacer adds space in the form of a tube or “chamber” between the canister of medication and the patient’s mouth, allowing the patient to inhale the medication...
or as a dry powder inhaler
Dry powder inhaler
A Dry powder inhaler is a device that delivers medication to the lungs in the form of a dry powder. DPIs are commonly used to treat respiratory diseases such as asthma, bronchitis, emphysema and COPD although DPIs have also been used in the treatment of diabetes mellitus.DPIs are an alternative...
. The spacer is a plastic cylinder that mixes the medication with air, making it easier to receive a full dose of the drug. A nebulizer
Nebulizer
In medicine, a nebulizer is a device used to administer medication in the form of a mist inhaled into the lungs....
may also be used. Nebulizers and spacers are equally effective in those with mild to moderate symptoms however insufficient evidence is available to determine whether or not a difference exists in those severe symptomatology.
Safety and adverse effects
Long-term use of glucocorticoids carries a significant potential for adverse effects. The incidence of cataract
Cataract
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
s is increased in people undergoing treatment for asthma with corticosteroids, due to altered regulation of lens epithelial cells. The incidence of osteoporosis
Osteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...
is also increased, due to changes in bone remodeling
Bone remodeling
Bone remodeling is a lifelong process where mature bone tissue is removed from the skeleton and new bone tissue is formed...
.
Other
When asthma is unresponsive to usual medications, other options are available for both emergency management and prevention of flairs. For emergency management other options include:- OxygenOxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
is used to alleviate hypoxiaHypoxia (medical)Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
if saturationsOxygen saturationOxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.It has particular significance in medicine and...
fall below 92%. - Magnesium sulfateMagnesium sulfateMagnesium sulfate is a chemical compound containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate epsomite , commonly called Epsom salt, from the town of Epsom in Surrey, England, where the salt was distilled from the springs that arise where the...
intravenous treatment has been shown to provide a bronchodilating effect when used in addition to other treatment in severe acute asthma attacks. - HelioxHelioxHeliox is a breathing gas composed of a mixture of helium and oxygen .Heliox has been used medically since the 1930s, and although the medical community adopted it initially to alleviate symptoms of upper airway obstruction, its range of medical uses has since expanded greatly, mostly because of...
, a mixture of helium and oxygen, may also be considered in severe unresponsive cases. - Intravenous salbutamol is not supported by available evidence and is thus used only in extreme cases.
- Methylxanthines (such as theophyllineTheophyllineTheophylline, also known as dimethylxanthine, is a methylxanthine drug used in therapy for respiratory diseases such as COPD and asthma under a variety of brand names. Because of its numerous side-effects, the drug is now rarely administered for clinical use. As a member of the xanthine family, it...
) were once widely used, but do not add significantly to the effects of inhaled beta-agonists. - The dissociative anesthetic ketamineKetamineKetamine is a drug used in human and veterinary medicine. Its hydrochloride salt is sold as Ketanest, Ketaset, and Ketalar. Pharmacologically, ketamine is classified as an NMDA receptor antagonist...
is theoretically useful if intubationIntubationTracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...
and mechanical ventilationMechanical ventilationIn medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
is needed in people who are approaching respiratory arrest; however, there is no evidence from clinical trials to support this.
For those with severe persistent asthma not controlled by inhaled corticosteroids and LABAs bronchial thermoplasty
Bronchial thermoplasty
Bronchial thermoplasty is a treatment for severe asthma approved by the FDA in 2010 involving the delivery of controlled, therapeutic radiofrequency energy to the airway wall, thus heating the tissue and reducing the amount of smooth muscle present in the airway wall...
can lead to clinical improvements. It involves the delivery of controlled thermal energy to the airway wall during a series of bronchoscopies
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
and result in a prolonged reduction in airway smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
mass.
Complementary medicine
Many people with asthma, like those who suffer from other chronic disorders, use alternative treatmentsAlternative medicine
Alternative medicine is any healing practice, "that does not fall within the realm of conventional medicine." It is based on historical or cultural traditions, rather than on scientific evidence....
; surveys show that roughly 50% of asthma patients use some form of unconventional therapy. There is little data to support the effectiveness of most of these therapies. Evidence is insufficient to support the usage of Vitamin C. Acupuncture
Acupuncture
Acupuncture is a type of alternative medicine that treats patients by insertion and manipulation of solid, generally thin needles in the body....
is not recommended for the treatment as there is insufficient evidence to support its use. Air ioniser
Air ioniser
An air ioniser is a device that uses high voltage to ionise air molecules. Negative ions, or anions, are particles with one or more extra electrons, conferring a net negative charge to the particle. Cations are positive ions missing one or more electrons, resulting in a net positive charge...
s show no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators.
Dust mite control measures, including air filtration, chemicals to kill mites, vacuuming, mattress covers and others methods had no effect on asthma symptoms. However, a review of 30 studies found that "bedding encasement might be an effective asthma treatment under some conditions" (when the patient is highly allergic to dust mite and the intervention reduces the dust mite exposure level from high levels to low levels). Washing laundry/rugs in hot water was also found to improve control of allergens.
A study of "manual therapies" for asthma, including osteopathic
Osteopathy
Osteopathy and osteopathic medicine are often used interchangeably for the philosophy and system of alternative medical practice first proposed by A. T. Still MD, DO in 1874....
, chiropractic
Chiropractic
Chiropractic is a health care profession concerned with the diagnosis, treatment and prevention of disorders of the neuromusculoskeletal system and the effects of these disorders on general health. It is generally categorized as complementary and alternative medicine...
, physiotherapeutic
Physical therapy
Physical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
and respiratory therapeutic
Respiratory therapy
Respiratory therapy is a healthcare profession in which specialists work with patients suffering from either acute or chronic respiratory problems. These specialists are termed Respiratory Therapists in most places internationally but may also be referred to as Respiratory Scientists or...
manoeuvres, found there is insufficient evidence to support their use in treating. The Buteyko breathing technique for controlling hyperventilation may result in a reduction in medications use however does not have any effect on lung function. Thus an expert panel felt that evidence was insufficient to support its use.
Prognosis
The prognosis for asthma is good, especially for children with mild disease. Of asthma diagnosed during childhood, 54% of cases will no longer carry the diagnosis after a decade. The extent of permanent lung damage in people with asthma is unclear. Airway remodeling is observed, but it is unknown whether these represent harmful or beneficial changes. Although conclusions from studies are mixed, most studies show that early treatment with glucocorticoids prevents or ameliorates decline in lung function as measured by several parameters.For those who continue to suffer from mild symptoms, corticosteroids can help most to live their lives with few disabilities
Disability
A disability may be physical, cognitive, mental, sensory, emotional, developmental or some combination of these.Many people would rather be referred to as a person with a disability instead of handicapped...
. It is more likely to consider immediate medication of inhaled corticosteroids as soon as asthma attacks occur. According to studies conducted, patients with relatively mild asthma who have received inhaled corticosteroids within 12 months of their first asthma symptoms achieved good functional control of asthma after 10 years of individualized therapy as compared to patients who received this medication after 2 years (or more) from their first attacks. Though they (delayed) also had good functional control of asthma, they were observed to exhibit slightly less optimal disease control and more signs of airway inflammation.
Asthma mortality has decreased over the last few decades due to better recognition and improvement in care.
Epidemiology
It is estimated that asthma has a 7-10% prevalence worldwide. As of 1998, there was a great disparity in the prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...
of asthma across the world, with a trend toward more developed
Developed country
A developed country is a country that has a high level of development according to some criteria. Which criteria, and which countries are classified as being developed, is a contentious issue...
and westernized
Western world
The Western world, also known as the West and the Occident , is a term referring to the countries of Western Europe , the countries of the Americas, as well all countries of Northern and Central Europe, Australia and New Zealand...
countries having higher rates of asthma, with as high as a 20 to 60-fold difference. Westernization however does not explain the entire difference in asthma prevalence between countries, and the disparities may also be affected by differences in genetic, social and environmental risk factors. Mortality however is most common in low to middle income countries, while symptoms were most prevalent (as much as 20%) in the United Kingdom, Australia, New Zealand, and Republic of Ireland; they were lowest (as low as 2–3%) in Eastern Europe, Indonesia, Greece, Uzbekistan, India, and Ethiopia.
While asthma is more common in affluent countries, it is by no means a restricted problem; the WHO estimate that there are between 15 and 20 million people with asthma in India. In the U.S., urban residents, Hispanics, and African Americans are affected more than the population as a whole. Striking increases in asthma prevalence have been observed in populations migrating from a rural environment to an urban one, or from a third-world country to Westernized one.
Asthma affects approximately 7% of the population of the United States and 5% of people in the United Kingdom. Asthma causes 4,210 deaths per year in the United States. In 2005 in the United States asthma affected more than 22 million people including 6 million children. It accounted for nearly 1/2 million hospitalizations that same year. More boys have asthma than girls, but more women have it than men. Of all children, African Americans and Latinos who live in cities are more at risk for developing asthma. African American children in the U.S. are four times more likely to die of asthma and three times more likely to be hospitalized, compared to their white counterparts. In some Latino neighborhoods, as many as one in three children has been found to have asthma.
In England, an estimated 261,400 people were newly diagnosed with asthma in 2005; 5.7 million people had an asthma diagnosis and were prescribed 32.6 million asthma-related prescriptions.
The frequency of atopic dermatitis, asthma, urticaria and allergic contact dermatitis has been found to be lower in psoriatic
Psoriasis
Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
patients.
Increasing frequency
Rates of asthma have increased significantly between the 1960s and 2008. Some 9% of US children had asthma in 2001, compared with just 3.6% in 1980. The World Health OrganizationWorld Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO) reports that some 10% of the Swiss population suffers from asthma today, compared with just 2% some 25–30 years ago. In the United States specifically data from several national surveys in the United States reveal the age-adjusted prevalence of asthma increased from 7.3 to 8.2 percent during the years 2001 through 2009
. Previous analysis of data from 2001 to 2007 had suggested the prevalence of asthma was stable.
Variability
Asthma prevalence in the US is higher than in most other countries in the world, but varies drastically between diverse US populations. In the US, asthma prevalence is highest in Puerto Ricans, African Americans, Filipinos, Irish Americans, and Native Hawaiians, and lowest in Mexicans and Koreans. Mortality rates follow similar trends, and response to salbutamolSalbutamol
Salbutamol or albuterol is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. It is marketed as Ventolin among other brand names....
is lower in Puerto Ricans than in African Americans or Mexicans. As with worldwide asthma disparities, differences in asthma prevalence, mortality, and drug response in the US may be explained by differences in genetic, social and environmental risk factors.
Asthma prevalence also differs between populations of the same ethnicity who are born and live in different places. US-born Mexican populations, for example, have higher asthma rates than non-US born Mexican populations that are living in the US.
There is no correlation between asthma and gender in children. More adult women are diagnosed with asthma than adult men, but this does not necessarily mean that more adult women have asthma.
History
Asthma was first recognized and named by HippocratesHippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...
circa 450 BC. During the 1930s–50s, asthma was considered as being one of the 'holy seven' psychosomatic illness
Psychosomatic illness
Psychosomatic medicine is an interdisciplinary medical field studying the relationships of social, psychological, and behavioral factors on bodily processes and well-being in humans and animals...
es. Its aetiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
was considered to be psychological, with treatment often based on psychoanalysis and other 'talking cure
Talking cure
The Talking Cure was a term originally offered, along with "chimney sweep", by Dr. Josef Breuer's patient Bertha Pappenheim to describe the talking therapy that relieved her of her hysterical symptoms...
s'. As these psychoanalysts interpreted the asthmatic wheeze as the suppressed cry of the child for its mother, so they considered that the treatment of depression was especially important for individuals with asthma. among the first papers in modern medicine, is one that was published in 1873 and this paper tried to explain the pathophysiology
Pathophysiology
Pathophysiology is the study of the changes of normal mechanical, physical, and biochemical functions, either caused by a disease, or resulting from an abnormal syndrome...
of the disease. And one of the first papers discussing treatment of asthma was released in 1872, the author concluded in his paper that asthma can be cured by rubbing the chest with chloroform liniment
A.B.C. Liniment
A.B.C. Liniment is a very old rubbing mixture or liniment. It was used for a long period of time as a way of relieving pain caused by lumbago , sciatica, neuralgia, rheumatism, stiffness after exercise and other conditions...
.
Among the first times researchers referred to medical treatment was in 1880, when Dr. J. B. Berkart used IV therapy
Intravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
to administer doses of a drug called pilocarpin. In 1886, F.H. Bosworth FH suspected a connection between asthma and hay fever
Hay Fever
Hay Fever is a comic play written by Noël Coward in 1924 and first produced in 1925 with Marie Tempest as the first Judith Bliss. Laura Hope Crews played the role in New York...
. Epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...
was first referred to in the treatment of asthma in 1905, and for acute asthma in 1910.