Sleep and breathing
Encyclopedia
Significant physiologic changes in breathing
take place during normal sleep
related to alterations in respiratory drive and musculature.
is higher and ventilation
is lower in sleep. Sleep onset
in normal subjects is not immediate, but oscillates between arousal
, stage I and II sleep before steady NREM sleep is obtained. So falling asleep results in decreased ventilation and a higher pCO2, above the wakefulness set point. On wakefulness, this constitutes an error signal which provokes hyperventilation
until the wakefulness set point is reached. When the subject falls asleep, ventilation decreases and pCO2 rises, resulting in hypoventilation or even apnea. These oscillations continue until steady state sleep is obtained.
contribution to ventilation increases during NREM sleep, mostly by lateral movement, and is detected by an increase in EMG amplitude during breathing. Diaphragm
activity is little increased or unchanged and abdominal muscle activity is slightly increased during these sleep stages.
increases by about 230% during NREM sleep. Elastic and flow resistive properties of the lung
do not change during NREM sleep. The increase in resistance comes primarily from the upper airway in the retroepiglottic region. Tonic activity of the pharyngeal
dilator muscles of the upper airway decreases during the NREM sleep, contributing to the increased resistance, which is reflected in increased esophageal
pressure swings during sleep. The other ventilatory muscles compensate for the increased resistance, and so the airflow decreases much less than the increase in resistance.
ses pCO2 increases by 3-7mmHg, pO2 drops by 3-9mmHg and SaO2 drops by 2% or less. These changes occur despite a reduced metabolic rate
, reflected by a 10-20% decrease in O2 consumption, suggesting overall hypoventilation
instead of decreased production/metabolism
.
occur with respiration
. Pulmonary arterial systolic and diastolic pressure and PAD increase by 4-5mm in NREM sleep
Increase EMG
activity of the diaphragm 150%, increased activity of upper airway dilating muscles 250%, increased airflow and tidal volume 160% and decreased upper airway resistance.
s lasting 10-30 seconds are noted in Rapid Eye Movement (REM) sleep. (These are physiologic changes and are different from abnormal breathing patterns noted in sleep disordered breathing). These breathing irregularities are not random, but correspond to bursts of eye movements. This breathing pattern is not controlled by the chemoreceptors
, but is due to the activation of behavioral respiratory control system
by REM sleep processes. Quantitative measure of airflow is quite variable in this sleep stage and has been shown to be increased, decreased or unchanged. Tidal volume has also been shown to be increased, decreased or unchanged by quantitative measures in REM sleep. So breathing during REM sleep is somewhat discordant.
due to hypoventilation is noted in REM sleep but this is less well studied than NREM sleep. These changes are equal to or greater than NREM sleep
is a condition characterized by noisy breathing during sleep. Usually, any medical condition where the normal airway is blocked during sleeping, like obstructive sleep apnea, gives rise to snoring. Snoring, when not associated with any such Obstructive phenomenon is known as Primary Snoring. Apart from the specific condition of Obstructive Sleep Apnoea, other causes of snoring include alcohol intake prior to sleeping, stuffy nose, sinusitis
, obesity, long tongue or uvula, large tonsil or adenoid, smaller lower jaw, deviated nasal septum
, asthma, smoking and sleeping on one's back. Primary Snoring is also known as Simple Snoring or Benign Snoring, and is not associated with sleep apnea, ie, temporary cessation of breathing.
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...
take place during normal sleep
Sleep
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...
related to alterations in respiratory drive and musculature.
Sleep onset
Set point of ventilation is different in wakefulness and sleep. pCO2Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
is higher and ventilation
Ventilation (physiology)
In respiratory physiology, ventilation is the rate at which gas enters or leaves the lung. It is categorized under the following definitions:-Sample values:...
is lower in sleep. Sleep onset
Sleep onset latency
In sleep science, sleep onset latency is the length of time that it takes to accomplish the transition from full wakefulness to sleep, normally to the lightest of the non-REM sleep stages.-Sleep latency studies:...
in normal subjects is not immediate, but oscillates between arousal
Arousal
Arousal is a physiological and psychological state of being awake or reactive to stimuli. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of...
, stage I and II sleep before steady NREM sleep is obtained. So falling asleep results in decreased ventilation and a higher pCO2, above the wakefulness set point. On wakefulness, this constitutes an error signal which provokes hyperventilation
Hyperventilation
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...
until the wakefulness set point is reached. When the subject falls asleep, ventilation decreases and pCO2 rises, resulting in hypoventilation or even apnea. These oscillations continue until steady state sleep is obtained.
Ventilation
Breathing is remarkably regular, both in amplitude and frequency in steady NREM sleep. Steady NREM sleep has the lowest indices of variability of all sleep stages. Minute ventilation decreases by 13% in steady stage II sleep and by 15% in steady slow wave sleep (Stage III and Stage IV sleep). Mean inspiratory flow is decreased but inspiratory duration and respiratory cycle duration are unchanged, resulting in an overall decreased tidal volume.Rib cage and abdominal muscle contributions
Rib cageHuman rib cage
-See also:*Terms for bones*Terms for anatomical location*Articulation of head of rib-References:* Clinically Oriented Anatomy, 4th ed. Keith L. Moore and Robert F. Dalley. pp. 62–64...
contribution to ventilation increases during NREM sleep, mostly by lateral movement, and is detected by an increase in EMG amplitude during breathing. Diaphragm
Thoracic diaphragm
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
activity is little increased or unchanged and abdominal muscle activity is slightly increased during these sleep stages.
Upper airway resistance
Airway resistanceAirway resistance
Airway resistance is a concept used in respiratory physiology to describe mechanical factors which limit the access of inspired air to the pulmonary alveoli, and thus determine airflow....
increases by about 230% during NREM sleep. Elastic and flow resistive properties of the 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...
do not change during NREM sleep. The increase in resistance comes primarily from the upper airway in the retroepiglottic region. Tonic activity of the pharyngeal
Human pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
dilator muscles of the upper airway decreases during the NREM sleep, contributing to the increased resistance, which is reflected in increased esophageal
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
pressure swings during sleep. The other ventilatory muscles compensate for the increased resistance, and so the airflow decreases much less than the increase in resistance.
Arterial blood gases
The Arterial blood gasArterial 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...
ses pCO2 increases by 3-7mmHg, pO2 drops by 3-9mmHg and SaO2 drops by 2% or less. These changes occur despite a reduced metabolic rate
Basal metabolic rate
Basal Metabolic Rate , and the closely related resting metabolic rate , is the amount of daily energy expended by humans and other animals at rest. Rest is defined as existing in a neutrally temperate environment while in the post-absorptive state...
, reflected by a 10-20% decrease in O2 consumption, suggesting overall hypoventilation
Hypoventilation
In medicine, hypoventilation occurs when ventilation is inadequate to perform needed gas exchange...
instead of decreased production/metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
.
Pulmonary arterial pressure
Periodic oscillations of the pulmonary arterial pressureBlood 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...
occur with respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
. Pulmonary arterial systolic and diastolic pressure and PAD increase by 4-5mm in NREM sleep
Effects of arousals
Induced transient arousal from NREM sleep cause the following:Increase EMG
Electromyography
Electromyography is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph, to produce a record called an electromyogram. An electromyograph detects the electrical potential generated by muscle...
activity of the diaphragm 150%, increased activity of upper airway dilating muscles 250%, increased airflow and tidal volume 160% and decreased upper airway resistance.
Ventilation
Irregular breathing with sudden changes in both amplitude and frequency at times interrupted by central apneaApnea
Apnea, apnoea, or apnœa is a term for suspension of external breathing. During apnea there is no movement of the muscles of respiration and the volume of the lungs initially remains unchanged...
s lasting 10-30 seconds are noted in Rapid Eye Movement (REM) sleep. (These are physiologic changes and are different from abnormal breathing patterns noted in sleep disordered breathing). These breathing irregularities are not random, but correspond to bursts of eye movements. This breathing pattern is not controlled by the chemoreceptors
Chemosensor
A chemoreceptor, also known as chemosensor, is a sensory receptor that transduces a chemical signal into an action potential. In more general terms, a chemosensor detects certain chemical stimuli in the environment.- Classes :...
, but is due to the activation of behavioral respiratory control system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
by REM sleep processes. Quantitative measure of airflow is quite variable in this sleep stage and has been shown to be increased, decreased or unchanged. Tidal volume has also been shown to be increased, decreased or unchanged by quantitative measures in REM sleep. So breathing during REM sleep is somewhat discordant.
Rib cage and abdominal muscle contributions
Intercostal muscle activity decreases in REM sleep and contribution of rib cage to respiration decreases during REM sleep. This is due to REM related supraspinal inhibition of alpha motoneuron drive and specific depression of fusimotor function. Diaphraghmatic activity correspondingly increases during REM sleep. Although paradoxical thoracoabdominal movements are not observed, the thoracic and abdominal displacements are not exactly in phase. This decrease in intercostal muscle activity is primarily responsible for hypoventilation that occurs in patients with borderline pulmonary function.Upper airway function
Upper airway resistance is expected to be highest during REM sleep because of atonia of the pharyngeal dilator muscles and partial airway collapse. Many studies have shown this, but not all. Some have shown unchanged airway resistance during REM sleep, others have shown it to increase to NREM levels.Arterial blood gases
HypoxemiaHypoxemia
Hypoxemia is generally defined as decreased partial pressure of oxygen in blood, sometimes specifically as less than or causing hemoglobin oxygen saturation of less than 90%.-Distinction from anemia and hypoxia:...
due to hypoventilation is noted in REM sleep but this is less well studied than NREM sleep. These changes are equal to or greater than NREM sleep
Pulmonary arterial pressure
Pulmonary arterial pressure fluctuates with respiration and rises during REM sleep.Effect of arousals
Arousals cause return of airway resistance and airflow to near awake values. Refer arousals in NREM sleep.Primary snoring
SnoringSnoring
Snoring is the vibration of respiratory structures and the resulting sound, due to obstructed air movement during breathing while sleeping. In some cases the sound may be soft, but in other cases, it can be loud and unpleasant...
is a condition characterized by noisy breathing during sleep. Usually, any medical condition where the normal airway is blocked during sleeping, like obstructive sleep apnea, gives rise to snoring. Snoring, when not associated with any such Obstructive phenomenon is known as Primary Snoring. Apart from the specific condition of Obstructive Sleep Apnoea, other causes of snoring include alcohol intake prior to sleeping, stuffy nose, sinusitis
Sinusitis
Sinusitis 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...
, obesity, long tongue or uvula, large tonsil or adenoid, smaller lower jaw, deviated nasal septum
Nasal septum
The nasal septum separates the left and right airways in the nose, dividing the two nostrils.It is depressed by the Depressor septi nasi muscle.-Composition:The fleshy external end of the nasal septum is sometimes also called columella....
, asthma, smoking and sleeping on one's back. Primary Snoring is also known as Simple Snoring or Benign Snoring, and is not associated with sleep apnea, ie, temporary cessation of breathing.
Upper airway resistance syndrome
Obstructive sleep apnea (including hypopnea) syndrome
Sleep apneaSleep apnea
Sleep apnea is a sleep disorder characterized by abnormal pauses in breathing or instances of abnormally low breathing, during sleep. Each pause in breathing, called an apnea, can last from a few seconds to minutes, and may occur 5 to 30 times or more an hour. Similarly, each abnormally low...