BiPAP / VPAP (Bilevel Positive Airway Pressure)

A device that delivers two separate pressures — a higher one for inhaling (IPAP), a lower one for exhaling (EPAP) — rather than one fixed pressure. Prescribed when standard CPAP isn't sufficient or comfortable, or for central and complex sleep apnea.

"VPAP" is ResMed's brand name for the same bilevel category; the underlying mechanism is the same across manufacturers.