Knowledge base

Support & learning library

42 articles and definitions, written for newly diagnosed users and veterans alike. Browse a category or search a term.

22 articles
20 glossary terms
6 categories

Getting started

If you were just diagnosed — start here.

Mask types

Pillow, nasal, full-face, hybrid — when each one wins.

Fit & comfort

Leaks, marks, headgear tension, side-sleeping.

Therapy basics

Pressure, ramp, humidification, EPR.

Buying & insurance

Prescriptions, retailers, replacement schedules.

Reviews & data

How summaries are generated and who submits them.

Glossary

Plain-English definitions of every CPAP term.

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AHI · Apnea-Hypopnea Index
Average number of apnea or hypopnea events per hour of sleep. Below 5 is normal; 5–15 is mild OSA; 15–30 is moderate; above 30 is severe.
APAP · Auto-titrating CPAP
A machine that adjusts pressure breath-by-breath within a prescribed range, rather than holding one fixed pressure all night.
BiPAP · Bi-level Positive Airway Pressure
Delivers a higher pressure during inhale and a lower one during exhale. Often prescribed when standard CPAP feels hard to exhale against.
Cushion
The silicone or memory-foam piece that contacts your face and forms the seal. Wears out every 1–3 months.
Deadspace
The volume of air trapped between cushion and vent. Lower deadspace means CO₂ is flushed more efficiently with each breath.
EPR · Expiratory Pressure Relief
A ResMed comfort feature that drops pressure slightly when you exhale. Philips calls their version Flex.
Frame
The plastic skeleton that holds the cushion and connects to the headgear. Replaceable as a wear part.
Full-face mask
Covers both nose and mouth. Required for mouth breathers or those at high prescribed pressures.
Headgear
The fabric straps that hold the mask in place. Should be snug, not tight — over-tightening causes more leaks than it fixes.
Hose · Tubing / circuit
Connects the machine to the mask. Heated tubing prevents rainout in cold rooms.
Hybrid mask
A mask that seals under the nose (like a pillow) but also covers the mouth. Smaller profile than a true full-face.
Leak rate
Liters per minute of unintended airflow escaping the seal. Most machines report this nightly; under 24 L/min is generally fine.
Mouth breather
Someone whose mouth opens during sleep. Tends to need full-face masks, hybrid masks, or nasal masks paired with a chin strap.
Nasal mask
Covers the nose only, sealing on the bridge and upper lip. The middle ground between pillows and full-face.
Nasal pillow
Small silicone inserts that seal at the nostril opening rather than over the nose. Minimal facial contact.
OSA · Obstructive Sleep Apnea
The most common form of sleep apnea, caused by the throat tissue collapsing during sleep.
Ramp
A comfort feature that starts pressure low and builds to the prescribed level over 5–45 minutes, helping you fall asleep.
Rainout
Water condensing in the hose from the heated humidifier. Fixed with heated tubing or a hose cover.
Titration
The process of finding the right pressure for you — done in a sleep lab, or automatically by an APAP over the first few weeks.
Vent
The intentional holes in the mask that flush exhaled CO₂. Quieter on newer designs but never silent.