Apnea
Apnea | |
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Other names | Apnoea |
A 32 s breathing pause in a sleep apnea patient | |
Specialty | Pulmonology, pediatrics |
Apnea,
Cause
Apnea can be involuntary—for example,
Apnea can also be observed during periods of heightened
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.
Voluntary apnea can be achieved by closing the
Complications
Under normal conditions,
Untrained humans usually cannot sustain voluntary apnea for more than one or two minutes, since the urge to breathe becomes unbearable.[citation needed] The reason for the time limit of voluntary apnea is that the rate of breathing and the volume of each breath are tightly regulated to maintain constant values of CO2 tension and pH of the blood more than oxygen levels. In apnea, CO2 is not removed through the lungs and accumulates in the blood. The consequent rise in CO2 tension and drop in pH result in stimulation of the respiratory centre in the brain which eventually cannot be overcome voluntarily. The accumulation of carbon dioxide in the lungs will eventually irritate and trigger impulses from the respiratory center part of the brain and the phrenic nerve. Rising levels of carbon dioxide signal the body to breathe and resume unconscious respiration forcibly. The lungs start to feel as if they are burning, and the signals the body receives from the brain when CO2 levels are too high include strong, painful, and involuntary contractions or spasms of the diaphragm and the muscles in between the ribs. At some point, the spasms become so frequent, intense and unbearable that continued holding of the breath is nearly impossible.[citation needed]
When a person is immersed in water, physiological changes due to the mammalian
Hyperventilation
Voluntary
Apneic oxygenation
Because the exchange of gases between the blood and airspace of the lungs is independent of the movement of gas to and from the lungs, enough oxygen can be delivered to the circulation even if a person is apneic, even if the diaphragm does not move. 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.[6]
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 hour's duration in a healthy adult.[citation needed] However, accumulation of carbon dioxide (described above) would remain the limiting factor.
Apneic oxygenation is more than a physiologic curiosity. It can be employed to provide a sufficient amount of oxygen in
In 1959, Frumin described the use of apneic oxygenation during anesthesia and surgery. Of the eight test subjects in this landmark study, the highest recorded
Apnea scientific studies
Studies found spleen volume is slightly reduced during short breath-hold apnea in healthy adults.[9]
Apnea test in determining brain death
A recommended practice for the clinical diagnosis of
Etymology and pronunciation
The word apnea (or apnoea) uses
See also
References
- ^ "Sleep apnoea". nhs.uk. 15 August 2019. Retrieved 21 April 2020.
- ^ "Sleep apnoea and orthodontics". Orthodontics Australia. 7 June 2021. Retrieved 28 February 2022.
- ^ "The Dangers of Uncontrolled Sleep Apnea". www.hopkinsmedicine.org. 10 March 2022. Retrieved 28 April 2022.
- ^ "Where is it". Archived from the original on 27 September 2008. Retrieved 2 March 2008. for 214-metre diving record
- JSTOR 4450291.
- ^ "preoygenation, reoxygenation and Delayed Sequence Intubation in the Emergency Department". medscape.com.
- ^ Perioperative Medicine: Managing for Outcome. PerioperBy Mark F. Newman, Lee A. Fleisher, Mitchell P. Fink. p. 517.
- S2CID 33528267.
- ^ PMID 23840858.
- ^ American Academy of Neurology. "Practice Parameters: Determining Brain Death in Adults" Archived 6 February 2009 at the Wayback Machine. Published 1994. Accessed 2008-01-06.
- Nunn, J. F. (1993). Applied Respiratory Physiology (4th ed.). Butterworth-Heinemann. ISBN 0-7506-1336-X.
External links
- Sleep Apnea[permanent dead link], a resource from the Harvard Division of Sleep Medicine on Obstructive Sleep Apnea
- apneacalculator.com, information about Apnea and the apnea-calculator for clinical treatment of Obstructive Sleep Apnea
- Freediving Courses & Training in the UK, information about learning the sport of Freediving, the club is called Apneists UK
- DiveWise.Org Non-profit scientific and educational resource for apnea divers
- DAN Breath-Hold Workshop Divers Alert Network 2006 Breath-Hold Diving Workshop PDF