Researchers at the Mayo Clinic in the U.S. have identified a new form of sleep apnea that may be resistant to standard treatment for the condition.
Until now, researchers have identified two types of sleep apnea, obstructive sleep apnea and central sleep apnea.
Obstructive sleep apnea is the most common and happens when the throat muscles relax and the airway narrows, which momentarily cuts off breathing and causes loud snoring.
Central sleep apnea, is when the brain fails to send the proper signals to the muscles that control breathing.
The Mayo researchers have now discovered another 'Complex sleep apnea' which is a combination of both obstructive and central sleep apnea.
They have apparently observed for some time that there are patients who appear to have obstructive sleep apnea, but the continuous positive airway pressure (CPAP) is not effective and they still suffer from moderate to severe sleep apnea even with the best treatment.
CPAP acts like a pneumatic splint to open a patient's airway.
In a study of 223 patients referred to the Mayo Clinic sleep disorder center it was found that 15 percent of the patients had complex sleep apnea, 84 percent had obstructive sleep apnea and 0.4 percent had central sleep apnea.
Men are more likely to have complex sleep apnea.
Lead investigator Dr. Timothy Morgenthaler, a sleep medicine specialist and pulmonologist says there are patients who appear to have obstructive sleep apnea, but the continuous positive airway pressure (CPAP) is not effective and they still do not breathe properly.
Symptoms of central sleep apnea then appear and fragmented sleep results, due to frequent pauses in breathing.
Initially patients with complex sleep apnea can appear to have obstructive sleep apnea when they stop breathing 20 to 30 times per hour each night.
The complex sleep apnea patients had sleep and cardiovascular histories similar to the obstructive sleep apnea patients and also had fewer complaints about waking up after initially falling asleep than those with central sleep apnea.
Dr. Morgenthaler says the phenomenon has been observed for years, but an effective treatment for the condition has not yet been identified.
The study is the first to attempt to categorize these people, says Morgenthaler.
The findings will be published in the September issue of the journal Sleep.