With the onset of apnea, low pressure develops in the airspace of the lungs because more oxygen is absorbed than CO2 is released. With the airways closed or obstructed, this will lead to a gradual collapse of the lungs and suffocation. However, if the airways are open, any gas supplied to the upper airways will follow the pressure gradient and flow into the lungs to replace the oxygen consumed. If pure oxygen is supplied, this process will serve to replenish the oxygen stored in the lungs and resume sufficient ventilation. The uptake of oxygen into the blood will then remain at the usual level, and the normal functioning of the organs will not be affected. A detriment to this hyperoxygenation is the occurrence of nitrogen washout, which can lead to absorption atelectasis.However, no CO2 is removed during apnea. The partial pressure of CO2 in the airspace of the lungs will quickly equilibrate with that of the blood. As the blood is loaded with CO2 from the metabolism without a way to remove it, more and more CO2 will accumulate and eventually displace oxygen and other gases from the airspace. CO2 will also accumulate in the tissues of the body, resulting in respiratory acidosis. Under ideal conditions (i.e., if pure oxygen is breathed before onset of apnea to remove all nitrogen from the lungs, and pure supplemental oxygen is insufflated), apneic oxygenation could theoretically be sufficient to provide enough oxygen for survival of more than one hours duration in a healthy adult.
Apnea (BrE: apnoea) is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are (patency), there may or may not be a flow of gas between the lungs and the environment, but if theres sufficient flow, gas exchange within the lungs and cellular respiration wouldnt be severely affected. Voluntarily doing this is called holding ones breath. Apnea may first be diagnosed in childhood, and it is recommended to consult an ENT specialist, allergist or sleep physician to discuss symptoms when noticed; malformation and/or malfunctioning of the upper airways may be observed by an orthodontist. Cause
Apnea can be involuntary—for example, drug-induced (such as by opiate toxicity), mechanically / physiologically induced (for example, by strangulation or choking), or a consequence of neurological disease or trauma. During sleep, people with severe sleep apnea can have over thirty episodes of intermittent apnea per hour every night.Apnea can also be observed during periods of heightened emotion, such as during crying or accompanied by the Valsalva maneuver when a person laughs. Apnea is a common feature of sobbing while crying, characterised by slow but deep and erratic breathing followed by brief periods of breath holding when crying. Another example of apnea are breath-holding spells; these are sometimes emotional in cause and are usually observed in children as a result of frustration, emotional stress and other psychological extremes.