What is the mode of action of a c-pap machine for sleep apnea?

Positive Air: The CPAP machine provides a gentle stream of air to act as a pneumatic stent to hold open your airway during sleep. I use one myself and find it quite easy and comfortable. For those who cannot tolerate it, (and your md approves) i suggest that you see a dentist who is trained in treatment of sleep apnea. An oral appliance may be helpful for you.

Keep from choking: Obstructive sleep apnea, the kind treated with cpap, is caused by a relaxation of the neck muscles resulting in physical blockage of the airway. CPAP delivers pressure that stents the airways and keeps them open so you can breathe freely.