Central Sleep Apnea
Most discussions of sleep apnea focus on obstructive sleep apnea and its treatment. Sleep apneas, however, come in more than one form.
The sleeper who suffers from obstructive sleep apnea periodically struggles to breathe but is unable to inhale effectively because his or her airway has collapsed. The sleeper whose problem is central sleep apnea periodically doesn't breathe at all, or breathes so shallowly that oxygen intake is ineffectual. In either type of sleep apnea, the lack of oxygen usually causes the patient to wake up, 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 device. Treatment of the CSA patient is more challenging because the signal to the body to inhale is not being transmitted from the breathing center in the brain.
Sleep experts report that the great majority of central apnea patients also experience obstructive sleep apnea although the CSA may not be noted until the OSA is treated. In some cases the sleeping CSA patient displays not a periodic failure to breathe at all but a periodic shallow breathing or underbreathing that alternates with deep overbreathing, a condition known as Cheyne-Stokes breathing. Estimates vary as to the frequency of central sleep apnea. Some say it accounts for 20 percent of all cases of sleep apnea. Michael Coppola, M.D., a pulmonary, critical care and sleep disorders physician in Springfield, MA, who is a member of the American Sleep Apnea Association board of directors, questions that number.
"I don't think it's 20 percent," he said in a recent interview, "but it's significant."
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 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 Cheyne-Stokes breathing with noticeably shorter cycles than classical CSB.
- CSA induced by the use of certain drugs, typically opiates.
Type 4 usually disappears when the patient descends to lower altitudes, and type 5 is best treated by alteration or elimination of the drug regimen, the Mayo article said.
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.
"Central patients are more challenging," said Coppola. "The hard part of people going back and forth requires careful coordination between the breathing physician and the heart care specialist. It's critical that the sleep doctor coordinate with the cardiologist."
He paused, then added, "Unfortunately sleep medicine is often practiced in a tunnel."
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, Coppola noted. "You can't fix that with CPAP, but oxygen therapy usually helps," he said.
Aside from those patients, about half of those suffering from CSA can be managed on CPAP alone, Coppola said. In others, he continued, the CSA patient may be assisted by a device known as adaptive servo-ventilator, 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 overbreathing. The elimination of overbreathing discourages the shallow underbreathing that typically follows in classic examples of Cheyne-Stokes breathing..
The effect of using an unvented mask is much the same as the effect of breathing into a paper bag, a homespun technique slowing overbreathing, or hyperventilation, as it is technically known.
Rahul K. Kakkar, M.D., director of the Sleep Disorders Center of the North Florida-South Georgia Veterans Affairs Health System wrote in an article published online in 2009 by that two drugs found some times effective in the treatment of CSA: acetazolamide (Diamox) and theophyline (Theo-dur).But he also noted that in certain situations the best treatment of central sleep apnea is nothing at all.
"If the [CSA] patient is not symptomatic, observation may be the only appropriate step. This may be the case in patients who have central sleep apnea during sleep-wake transition, patients without significant oxygen desaturation, or those who experience central sleep apnea during continuous PAP (CPAP) treatment of obstructive sleep apnea."
Here are links to more information about central sleep apnea: