Disabled World: Revised/Updated: 2019/06/15
Synopsis: Information regarding sleep apnea, a sleep disorder characterized by prolonged pauses in breathing during sleep. Sleep apnea is diagnosed with an overnight sleep test called a polysomnogram, or a "Sleep Study". A CPAP machine assists inhaling. A BiPAP machine assists both inhaling and exhaling - and is used in more severe cases.
Sleep apnea (sleep apnoea in British English) is a sleep disorder characterized by pauses in breathing or instances of shallow or infrequent breathing during sleep.
Each pause in breathing, called an apnea, can last for several seconds to several minutes, and may occur 5 to 30 times or more in an hour. Each abnormally shallow breathing event is called a hypopnea.
Sleep apnea is classified as a dyssomnia, meaning abnormal behavior or psychological events occur during sleep. When breathing is paused, carbon dioxide builds up in the bloodstream. Chemo-receptors in the blood stream note the high carbon dioxide levels. The brain is signaled to wake the person sleeping and breathe in air. Breathing normally will restore oxygen levels and the person will fall asleep again. Sleep apnea is often diagnosed with an overnight sleep test called a polysomnogram, or sleep study.
There are three forms of Sleep Apnea: central, obstructive, and complex:
Fig 1. Illustration shows standard setup for a polysomnogram. In figure A, the patient lies in a bed with sensors attached to the body. In figure B, the polysomnogram recording shows blood oxygen level, breathing event, and rapid eye movement (REM) sleep stage over time - National Heart Lung and Blood Institute (NIH).
In central sleep apnea, the basic neurological controls for breathing rate malfunctions and fails to give the signal to inhale, causing the individual to miss one or more cycles of breathing.
If the pause in breathing is long enough, the percentage of oxygen in the circulation will drop to a lower than normal level (hypoxia) and the concentration of carbon dioxide will build to a higher than normal level (hypercapnia).
In turn, these conditions of hypoxia and hypercapnia will trigger additional effects on the body.
Common symptoms include loud snoring, restless sleep, and sleepiness during the daytime. Diagnostic tests include home oximetry or polysomnography in a sleep clinic.
The early reports of obstructive sleep apnea in the medical literature described individuals who were very severely affected, often presenting with severe hypoxemia, hypercapnia and congestive heart failure.
Tracheostomy was the recommended treatment and, though it could be life-saving, post-operative complications in the stoma were frequent.
Some treatments involve lifestyle changes, such as avoiding alcohol or muscle relaxants, losing weight, and quitting smoking.
Complex sleep apnea has recently been described by researchers as a novel presentation of sleep apnea.
Patients with complex sleep apnea exhibit OSA, but upon application of positive airway pressure, the patient exhibits persistent central sleep apnea. This central apnea is most commonly noted while on CPAP therapy, after the obstructive component has been eliminated. This has long been seen in sleep laboratories, and has historically been managed either by CPAP or Bi-Level therapy.
Adaptive servo-ventilation modes of therapy have been introduced to attempt to manage this complex sleep apnea. Studies have demonstrated marginally superior performance of the adaptive servo ventilators in treating Cheyne-Stokes breathing, however, no longitudinal studies have yet been published, nor have any results been generated which suggest any differential outcomes versus standard CPAP therapy.
The diagnosis of sleep apnea is based on the conjoint evaluation of clinical symptoms (e.g. excessive daytime sleepiness and fatigue) and of the results of a formal sleep study (polysomnography, or reduced channels home based test).
The latter aims at establishing an "objective" diagnosis indicator linked to the quantity of apneic events per hour of sleep (Apnea Hypopnea Index(AHI), or Respiratory Disturbance Index (RDI)), associated to a formal threshold, above which a patient is considered as suffering from sleep apnea, and the severity of their sleep apnea can then be quantified.
The most common treatment and arguably the most consistently effective treatment for sleep apnea is the use of a continuous positive airway pressure (CPAP) device, which splints the patient's airway open during sleep by means of a flow of pressurized air into the throat.
The CPAP machine only assists inhaling whereas a BiPAP machine assists with both inhaling and exhaling, and is used in more severe cases.
Severity of sleep apnea depends on how often the breathing is interrupted: