Most discussions of sleep apnea focus on obstructive sleep apnea (OSA) and its treatment. Sleep apneas, however, come in more than one form.
The sleeper who suffers from OSA periodically struggles to breathe but is unable to inhale effectively because his or her airway has become blocked or collapsed. The sleeper whose problem is central sleep apnea (CSA) periodically doesn’t breathe at all so oxygen intake is ineffectual. In either type of sleep apnea, the lack of oxygen usually causes the patient to wake up or arouse, at least briefly.
To put it another way, the OSA patient has a mechanical problem, one that almost always can be corrected by a continuous positive airway pressure (CPAP) device.
Treatment of CSA is more challenging because the signal to the body to inhale is not being transmitted from the breathing center in the brain, or not received by the body. Sleep experts report that the great majority of central apnea sufferers also experience OSA although the CSA may not be noted until the OSA is treated.
In some cases the sleeping CSA sufferer displays a periodic shallow breathing or under-breathing that alternates with deep over-breathing, a condition known as Cheyne-Stokes breathing (CSB) Estimates vary as to the frequency of central sleep apnea. Some say it accounts for 20 percent of all cases of sleep apnea.
The symptoms of central sleep apnea are for the most part the same as those of obstructive sleep apnea. They include chronic fatigue, daytime sleepiness, morning headaches and restless sleep. But if the cause is a neurological disease, the CSA sufferer may also experience difficulty swallowing, voice changes, and an overall sense of weakness and numbness. A thorough sleep study with polysomnography will show whether the lapses in breathing result from airway blockage or irregular breathe signals from the brain.
CSA frequently occurs among people who are seriously ill from other causes: chronic heart failure; diseases of and injuries to the brainstem; the upper terminus of the spine; which controls breathing; Parkinson’s Disease; stroke; kidney failure; even severe arthritis with degenerative changes to the cervical spine and base of the skull.
It is also seen among users of opiates. And there is idiopathic CSA, which simply means the cause is unknown. “For idiopathic apnea, the outlook is generally favorable,” notes Medline Plus, an online information service of the National Library of Medicine and the National Institutes of Health.
An online discussion of central sleep apnea prepared by experts at Minnesota’s Mayo Clinic breaks the disease down into five types:
- Primary CSA, which is the same as idiopathic CSA–the patient has no known related diseases.
- Cheyne-Stokes breathing CSA, which may be a product of heart failure, stroke, or possible kidney failure.
- Non-CSB CSA associated with other medical conditions, including heart and kidney problems.
- High-altitude CSA, which often appears during sleep at altitudes above 15,000 feet and induces a form of CSB with noticeably shorter cycles than classical CSB. Usually the CSB disappears when the person descends to lower altitudes.
- CSA induced by using certain drugs, typically opiates. May be best treated by alteration or elimination of the drug regimen.
Unfortunately, when CSA is a byproduct of some other disease, the outlook tends to be more discouraging, according to Medline Plus.
Treatment of these complex varieties of CSA generally call for aggressive treatment of the accompanying condition by another medical specialist, for example, a cardiologist in the case of heart failure.
In some cases effective treatment of the accompanying illness, if there is one, reduces or eliminates the CSA, but there are often treatments that the sleep physician can pursue in tandem. In cases where CSA is associated with heart failure, the patient sometimes has slow blood flow as well as erratic breathing and consequently is awakened frequently by a sheer lack of oxygen.
Aside from those patients, about half of those suffering from CSA can be managed on CPAP alone. The CSA patient may also be assisted by a device known as adaptive servo-ventilator (ASV), which monitors the patient‘s breathing and kicks in with extra pressure, which may be mixed with extra oxygen, when the normal respiration pattern breaks down.
Some patients are helped by unvented CPAP masks, which tend to raise the level of retained carbon dioxide in the blood. This in turn raises the blood’s acidity and that tends to damp down over-breathing. The elimination of over-breathing discourages the shallow under-breathing that typically follows in classic examples of CSB. The effect of using an unvented mask is much the same as the effect of breathing into a paper bag, a homespun technique slowing over-breathing, or hyper-ventilation, as it is technically known.