Continuous positive airway pressure -- also called CPAP – treats sleep apnea with a mask worn over your nose and/or mouth in bed. The mask is hooked up to a machine that delivers a continuous flow of air into the nose. This air flow helps keep the airways open so that breathing is regular. CPAP is the most common treatment for sleep apnea. There's also bi-level positive airway pressure, or BPAP, which is similar to CPAP but the air flow changes when you breathe in and then breathe out.