Hyperventilation
Encyclopedia
Hyperventilation or overbreathing is the state of breathing
faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide
. It can result from a psychological state such as a panic attack
, from a physiological condition such as metabolic acidosis
, can be brought about by lifestyle risk factors or voluntarily as in the yogic practice of Bhastrika. It often occurs together with labored breathing
, which, in contrast, can also be a response to increased carbon dioxide levels.
Hyperventilation can, but does not necessarily always cause symptoms such as numbness or tingling in the hands, feet and lips, lightheadedness
, dizziness, headache, chest pain, slurred speech, nervous laughter, and sometimes fainting, particularly when accompanied by the Valsalva maneuver
.
Counterintuitively, such effects are not precipitated by the sufferer's lack of oxygen or air. Rather, the hyperventilation itself reduces the carbon dioxide
concentration of the blood
to below its normal level because one is expiring more carbon dioxide
than being produced in the body, thereby raising the blood's pH
value (making it more alkaline), initiating constriction of the blood vessels which supply the brain, and preventing the transport of oxygen and other molecules necessary for the function of the nervous system
. At the same time, hypocapnia
causes a higher affinity of oxygen to haemoglobin, known as the Bohr effect
further reducing the amount of oxygen that is made available to the brain.
or anxiety
commonly are causes of hyperventilation; this is known as hyperventilation syndrome
. Hyperventilation can also be brought about voluntarily, by taking many deep breaths in rapid succession. Hyperventilation can also occur as a consequence of various lung
diseases, head injury, or stroke
(central neurogenic hyperventilation
, apneustic respirations
, ataxic respiration
, Cheyne-Stokes respirations or Biot's respiration
) and various lifestyle causes. In the case of metabolic acidosis
, the body uses hyperventilation as a compensatory mechanism to decrease acidity of the blood. In the setting of diabetic ketoacidosis
, this is known as Kussmaul breathing
- characterized by long, deep breaths.
Hyperventilation can also occur when someone exercises over their VO2 max
, when they're unable to transform oxygen into energy beyond a certain level but hyperventilates in an effort to do so.
In very general terms, hyperventilation is an increased alveolar ventilation. This not to be confused with the term hyperpnea which pertains to an increased minute ventilation.
Hyperventilation is not the same as hyperpnea
. In hyperpnea, increased ventilation is appropriate for a metabolic acidotic state, this is also known as respiratory compensation. Whereas in hyperventilation, increased ventilation is inappropriate for the metabolic state of blood plasma.
If carbon dioxide levels are high, the body assumes that oxygen levels are low, and accordingly, the brain's blood vessels dilate to assure sufficient blood flow and supply of oxygen. Conversely, low carbon dioxide levels cause the brain's blood vessels to constrict, resulting in reduced blood flow to the brain and lightheadedness.
The gases in the alveoli of the lungs are nearly in equilibrium with the gases in the blood
. Normally, less than 10% of the gas in the alveoli is replaced with each breath taken. Deeper or quicker breaths as in hyperventilation exchange more of the alveolar gas with ambient air and have the net effect of expelling more carbon dioxide from the body, since the carbon dioxide concentration in normal air is very low.
The resulting low concentration of carbon dioxide in the blood is known as hypocapnia
. Since carbon dioxide is carried as bicarbonate
in the blood, the loss of carbon dioxide will drive bicarbonate to combine with hydrogen ions (protons) to form more carbon dioxide. The loss of hydrogen ions results in the blood becoming alkaline, i.e. the blood pH value rises. This is known as a respiratory alkalosis
.
This alkalinization of the blood causes vessels to constrict (vasoconstriction
); it is theorized that myofibrillar calcium sensitivity is increased in the presence of high pH value.
The high pH value resulting from hyperventilation also reduces the level of available calcium
(hypocalcemia), which affects the nerves and muscles, causing constriction of blood vessels and tingling. This occurs because alkalinization of the plasma proteins (mainly albumin
) increases their calcium binding affinity, thereby reducing free ionized calcium levels in the blood. Therefore, low levels of carbon dioxide can cause tetany
by altering the albumin binding of calcium such that the ionised (physiologically influencing) fraction of calcium is reduced.
Therefore, there are two main mechanisms that contribute to the cerebral vasoconstriction that is responsible for the lightheadedness
, parasthesia, and fainting often seen with hyperventilation. One mechanism is that low carbon dioxide (hypocapnia
) causes increased blood pH level (respiratory alkalosis
), which causes blood vessels to constrict. The other mechanism is that the alkalosis causes decreased freely ionized blood calcium, thereby causing cell membrane instability and subsequent vasoconstriction and parasthesia.
Hyperventilation can be useful in the management of head trauma. After head injuries fluids can leak into the cranial vault, thus elevating intracranial pressure. Since the total cranial volume is relatively fixed, and the brain is much more compressible than the skull, in settings of increased intracranial pressure, the brain is preferentially compressed and damaged. Hyperventilation, and the resultant cerebral vasoconstriction, is useful in this situation, since it decreases the volume of blood in the brain. Less blood volume in the cranial cavity results in less pressure compressing the brain. However, this vasoconstriction comes at the cost of reducing blood flow to the brain, which can potentially result in ischemic damage.
is present supplemental oxygen
may be useful. If it is due to anxiety
as the cause of hyperventilation syndrome
, benzodiazepines may be useful.
Breathing
Breathing is the process that moves air in and out of the lungs. Aerobic organisms require oxygen to release energy via respiration, in the form of the metabolism of energy-rich molecules such as glucose. Breathing is only one process that delivers oxygen to where it is needed in the body and...
faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. It can result from a psychological state such as a panic attack
Panic attack
Panic attacks are periods of intense fear or apprehension that are of sudden onset and of relatively brief duration. Panic attacks usually begin abruptly, reach a peak within 10 minutes, and subside over the next several hours...
, from a physiological condition such as metabolic acidosis
Metabolic acidosis
In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low due to increased production of hydrogen by the body or the...
, can be brought about by lifestyle risk factors or voluntarily as in the yogic practice of Bhastrika. It often occurs together with labored breathing
Labored breathing
Labored respiration or labored breathing is an abnormal respiration characterized by evidence of increased effort to breathe, including the use of accessory muscles of respiration, stridor, grunting, or nasal flaring.-Classification:...
, which, in contrast, can also be a response to increased carbon dioxide levels.
Hyperventilation can, but does not necessarily always cause symptoms such as numbness or tingling in the hands, feet and lips, lightheadedness
Lightheadedness
Light-headedness is a common and often unpleasant sensation of dizziness and/or feeling that one may be about to faint, which may be transient, recurrent, or occasionally chronic. In some cases, the individual may feel as though his or her head is weightless. The individual may also feel as...
, dizziness, headache, chest pain, slurred speech, nervous laughter, and sometimes fainting, particularly when accompanied by the Valsalva maneuver
Valsalva maneuver
The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut...
.
Counterintuitively, such effects are not precipitated by the sufferer's lack of oxygen or air. Rather, the hyperventilation itself reduces the carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
concentration of the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
to below its normal level because one is expiring more carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
than being produced in the body, thereby raising the blood's pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
value (making it more alkaline), initiating constriction of the blood vessels which supply the brain, and preventing the transport of oxygen and other molecules necessary for the function of the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
. At the same time, hypocapnia
Hypocapnia
Hypocapnia or hypocapnea also known as hypocarbia, sometimes incorrectly called acapnia, is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation....
causes a higher affinity of oxygen to haemoglobin, known as the Bohr effect
Bohr effect
Bohr effect is a property of hemoglobin first described in 1904 by the Danish physiologist Christian Bohr , which states that an increasing concentration of protons and/or carbon dioxide will reduce the oxygen affinity of hemoglobin...
further reducing the amount of oxygen that is made available to the brain.
Causes
StressStress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...
or anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
commonly are causes of hyperventilation; this is known as hyperventilation syndrome
Hyperventilation syndrome
Hyperventilation syndrome is a respiratory disorder, psychologically or physiologically based, involving breathing too deeply or too rapidly...
. Hyperventilation can also be brought about voluntarily, by taking many deep breaths in rapid succession. Hyperventilation can also occur as a consequence of various lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
diseases, head injury, or stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
(central neurogenic hyperventilation
Central neurogenic hyperventilation
Central neurogenic hyperventilation is an abnormal pattern of breathing characterized by deep and rapid breaths at a rate of at least 25 breaths per minute. Increasing irregularity of this respiratory rate generally is a sign that the patient will enter into coma. CNH is unrelated to other forms...
, apneustic respirations
Apneustic respirations
Apneustic respiration is an abnormal pattern of breathing characterized by deep, gasping inspiration with a pause at full inspiration followed by a brief, insufficient release....
, ataxic respiration
Ataxic respiration
Ataxic respiration is an abnormal pattern of breathing characterized by complete irregularity of breathing, with irregular pauses and increasing periods of apnea. As the breathing pattern deteriorates, it merges with agonal respirations....
, Cheyne-Stokes respirations or Biot's respiration
Biot's respiration
Biot's respiration, sometimes also called ataxic respiration, is an abnormal pattern of breathing characterized by groups of quick, shallow inspirations followed by regular or irregular periods of apnea.It generally indicates a poor prognosis....
) and various lifestyle causes. In the case of metabolic acidosis
Acidosis
Acidosis is an increased acidity in the blood and other body tissue . If not further qualified, it usually refers to acidity of the blood plasma....
, the body uses hyperventilation as a compensatory mechanism to decrease acidity of the blood. In the setting of diabetic ketoacidosis
Diabetic ketoacidosis
Diabetic ketoacidosis is a potentially life-threatening complication in patients with diabetes mellitus. It happens predominantly in those with type 1 diabetes, but it can occur in those with type 2 diabetes under certain circumstances...
, this is known as Kussmaul breathing
Kussmaul breathing
Kussmaul breathing is a deep and labored breathing pattern often associated with severe metabolic acidosis, particularly diabetic ketoacidosis but also renal failure. It is a form of hyperventilation, which is any breathing pattern that reduces carbon dioxide in the blood due to increased rate or...
- characterized by long, deep breaths.
Hyperventilation can also occur when someone exercises over their VO2 max
VO2 max
VO2 max is the maximum capacity of an individual's body to transport and use oxygen during incremental exercise, which reflects the physical fitness of the individual...
, when they're unable to transform oxygen into energy beyond a certain level but hyperventilates in an effort to do so.
In very general terms, hyperventilation is an increased alveolar ventilation. This not to be confused with the term hyperpnea which pertains to an increased minute ventilation.
Hyperventilation is not the same as hyperpnea
Hyperpnea
Hyperpnea or hyperpnoea is increased depth of breathing when required to meet metabolic demand of body tissues, such as during or following exercise, or when the body lacks oxygen , for instance in high altitude or as a result of anemia....
. In hyperpnea, increased ventilation is appropriate for a metabolic acidotic state, this is also known as respiratory compensation. Whereas in hyperventilation, increased ventilation is inappropriate for the metabolic state of blood plasma.
Mechanism
In normal breathing, both the depth and frequency of breaths are varied by the neural (or, nervous) system, primarily in order to maintain normal amounts of carbon dioxide but also to supply appropriate levels of oxygen to the body's tissues. This is mainly achieved by measuring the carbon dioxide content of the blood; normally, a high carbon dioxide concentration signals a low oxygen concentration, as we breathe in oxygen and breathe out carbon dioxide at the same time, and the body's cells use oxygen to burn fuel molecules, making carbon dioxide as a by-product. Normal minute ventilation is generally 5-8 liters of air per minute at rest for a 70-kg man.If carbon dioxide levels are high, the body assumes that oxygen levels are low, and accordingly, the brain's blood vessels dilate to assure sufficient blood flow and supply of oxygen. Conversely, low carbon dioxide levels cause the brain's blood vessels to constrict, resulting in reduced blood flow to the brain and lightheadedness.
The gases in the alveoli of the lungs are nearly in equilibrium with the gases in the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
. Normally, less than 10% of the gas in the alveoli is replaced with each breath taken. Deeper or quicker breaths as in hyperventilation exchange more of the alveolar gas with ambient air and have the net effect of expelling more carbon dioxide from the body, since the carbon dioxide concentration in normal air is very low.
The resulting low concentration of carbon dioxide in the blood is known as hypocapnia
Hypocapnia
Hypocapnia or hypocapnea also known as hypocarbia, sometimes incorrectly called acapnia, is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation....
. Since carbon dioxide is carried as bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...
in the blood, the loss of carbon dioxide will drive bicarbonate to combine with hydrogen ions (protons) to form more carbon dioxide. The loss of hydrogen ions results in the blood becoming alkaline, i.e. the blood pH value rises. This is known as a respiratory alkalosis
Respiratory alkalosis
Respiratory alkalosis is a medical condition in which increased respiration elevates the blood pH...
.
This alkalinization of the blood causes vessels to constrict (vasoconstriction
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
); it is theorized that myofibrillar calcium sensitivity is increased in the presence of high pH value.
The high pH value resulting from hyperventilation also reduces the level of available calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
(hypocalcemia), which affects the nerves and muscles, causing constriction of blood vessels and tingling. This occurs because alkalinization of the plasma proteins (mainly albumin
Albumin
Albumin refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat denaturation. They are commonly found in blood plasma, and are unique to other blood proteins in that they are not glycosylated...
) increases their calcium binding affinity, thereby reducing free ionized calcium levels in the blood. Therefore, low levels of carbon dioxide can cause tetany
Tetany (medical sign)
Tetany is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disease or other conditions that increase the action potential frequency...
by altering the albumin binding of calcium such that the ionised (physiologically influencing) fraction of calcium is reduced.
Therefore, there are two main mechanisms that contribute to the cerebral vasoconstriction that is responsible for the lightheadedness
Lightheadedness
Light-headedness is a common and often unpleasant sensation of dizziness and/or feeling that one may be about to faint, which may be transient, recurrent, or occasionally chronic. In some cases, the individual may feel as though his or her head is weightless. The individual may also feel as...
, parasthesia, and fainting often seen with hyperventilation. One mechanism is that low carbon dioxide (hypocapnia
Hypocapnia
Hypocapnia or hypocapnea also known as hypocarbia, sometimes incorrectly called acapnia, is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation....
) causes increased blood pH level (respiratory alkalosis
Respiratory alkalosis
Respiratory alkalosis is a medical condition in which increased respiration elevates the blood pH...
), which causes blood vessels to constrict. The other mechanism is that the alkalosis causes decreased freely ionized blood calcium, thereby causing cell membrane instability and subsequent vasoconstriction and parasthesia.
Hyperventilation can be useful in the management of head trauma. After head injuries fluids can leak into the cranial vault, thus elevating intracranial pressure. Since the total cranial volume is relatively fixed, and the brain is much more compressible than the skull, in settings of increased intracranial pressure, the brain is preferentially compressed and damaged. Hyperventilation, and the resultant cerebral vasoconstriction, is useful in this situation, since it decreases the volume of blood in the brain. Less blood volume in the cranial cavity results in less pressure compressing the brain. However, this vasoconstriction comes at the cost of reducing blood flow to the brain, which can potentially result in ischemic damage.
Treatment
The first step that should be taken is to treat the underlying cause. If 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...
is present supplemental oxygen
Oxygen
Oxygen 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...
may be useful. If it is due to anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
as the cause of hyperventilation syndrome
Hyperventilation syndrome
Hyperventilation syndrome is a respiratory disorder, psychologically or physiologically based, involving breathing too deeply or too rapidly...
, benzodiazepines may be useful.
See also
- List of terms of lung size and activity
- HypoventilationHypoventilationIn medicine, hypoventilation occurs when ventilation is inadequate to perform needed gas exchange...
, too shallow or too slow breathing - Control of respirationControl of respirationControl of ventilation refers to the physiological mechanisms involved in the control of physiologic ventilation. Gas exchange primarily controls the rate of respiration.The most important function of breathing is gas exchange...
- Respiratory alkalosisRespiratory alkalosisRespiratory alkalosis is a medical condition in which increased respiration elevates the blood pH...
- Shallow water blackoutShallow water blackoutA shallow water blackout is a loss of consciousness caused by cerebral hypoxia towards the end of a breath-hold dive in water typically shallower than five metres , when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have...
, the role of hyperventilation in some drowning incidents - HyperpneaHyperpneaHyperpnea or hyperpnoea is increased depth of breathing when required to meet metabolic demand of body tissues, such as during or following exercise, or when the body lacks oxygen , for instance in high altitude or as a result of anemia....
- TachypneaTachypneaTachypnea means rapid breathing. Any rate between 12-20 breaths per minute is normal. Tachypnea is a respiration rate greater than 20 breaths per minute. - Distinction from other breathing terms :...