CPAP and sleep apnea glossary | VivaRespire

CPAP and Sleep Apnea Glossary

Medical sleep vocabulary can seem confusing. This glossary explains in plain language the terms you will encounter with your doctor, on your CPAP device, or in your insurance documents.

AHI - Apnea-Hypopnea Index: Measures the number of apneas and hypopneas per hour of sleep. The main indicator of sleep apnea severity. Thresholds: < 5 = normal, 5-15 = mild, 15-30 = moderate, > 30 = severe.
APAP (Auto-CPAP / AutoPAP): A CPAP variant that automatically adjusts pressure in real time based on detected respiratory events. More comfortable than fixed-pressure CPAP for most patients. Recommended as first-line therapy. See our Auto CPAP devices.
AirView: ResMed's remote monitoring platform allowing providers and physicians to review CPAP data remotely (residual AHI, leaks, usage hours). Integrated into ResMed devices via SIM card or Wi-Fi.
ASV (Adaptive Servo-Ventilation): A sophisticated ventilator that adapts pressure to each breath cycle to stabilize ventilation. Used for complex central apneas, Cheyne-Stokes breathing, and treatment-emergent central apneas resistant to standard CPAP.
Aerophagia: Swallowing air under pressure during CPAP therapy, causing bloating, gas, and belching. Often signals pressure that is too high. Solutions: reduce pressure (with medical advice), activate EPR/C-Flex, or try BiPAP.
BiPAP (Bi-Level PAP): Also called BiLevel or VPAP. A ventilation device with two pressure levels: a higher inspiratory pressure (IPAP) and a lower expiratory pressure (EPAP). Used for intolerance to CPAP back-pressure, central apneas, or respiratory insufficiency.
cmH₂O (centimeters of water): Unit of CPAP pressure measurement. CPAPs typically deliver between 4 and 20 cmH₂O depending on patient needs.
CPAP (Continuous Positive Airway Pressure): The gold-standard treatment for moderate to severe obstructive sleep apnea. A device delivers continuously pressurized air through a mask to keep the airways open during sleep.
CPAP Convention (INAMI/RIZIV Belgium): The Belgian INAMI convention is not a purchase reimbursement: it provides CPAP equipment through an approved sleep center - the patient never owns the device. Patient cost: €0.25/day. Criteria: IAHO ≥ 15/h, compliance ≥ 4h/night average. More details: CPAP reimbursement in Belgium.
EPAP (Expiratory Positive Airway Pressure): Pressure applied during expiration in a BiPAP system. Lower than IPAP, it keeps airways open without creating excessive resistance.
EPR (Expiratory Pressure Relief): ResMed technology that automatically reduces CPAP pressure during expiration (equivalent to C-Flex by Philips). Improves comfort. Available in 3 levels.
ESS (Epworth Sleepiness Scale): An 8-question survey measuring daytime sleepiness across daily situations. Score 0-24. Score ≥ 11: excessive daytime sleepiness requiring medical evaluation.
Hypopnea: Partial reduction of airflow (≥ 30%) lasting at least 10 seconds, associated with an oxygen desaturation or arousal. Less severe than a complete apnea but included in the AHI calculation.
IAHO (Belgian equivalent of AHI): Index d'Apnées-Hypopnées Obstructives - the preferred term in Belgian INAMI nomenclature. Adult INAMI criteria: IAHO ≥ 15/hour. Children (< 16 years): IAHO ≥ 1/hour.
INAMI / RIZIV: Belgium's National Institute for Health and Disability Insurance. Manages health insurance, including the CPAP convention criteria and approved sleep centers.
IPAP (Inspiratory Positive Airway Pressure): Pressure applied during inspiration in a BiPAP system. Higher than EPAP, it helps keep airways open and facilitates air entry into the lungs.
OAM (Mandibular Advancement Device / MAD): A custom dental device worn at night that advances the lower jaw to widen the upper airways. Second-line treatment for mild to moderate apnea, or as a CPAP alternative. Prescribed by a dentist specialized in sleep medicine.
OSCAR: Free open-source software for detailed analysis of CPAP data (residual AHI, leaks, pressure histogram, breathing waveform). Compatible with major manufacturers. Widely used by patients wanting to optimize their therapy.
OSA (Obstructive Sleep Apnea): Cessation of breathing for ≥ 10 seconds caused by collapse of the upper airways despite continued respiratory effort. Accounts for ~90% of sleep apnea cases. Effectively treated by CPAP.
Polygraphy (ambulatory): At-home sleep apnea screening test measuring airflow, thoracic movements, SpO2 and heart rate. Sufficient for diagnosis in most cases. Reimbursed by Belgian health insurance.
Polysomnography (PSG): The gold-standard sleep study conducted in a sleep center. Records EEG (brain activity), EMG (muscles), EOG (eye movements), airflow, respiratory movements, SpO2, and posture. Reimbursed by Belgian health insurance.
Rainout: Condensation forming in the CPAP tube when humidified air cools in transit. Causes gurgling and water droplets in the mask. Solution: heated tubing (ClimateLine, etc.) or tube insulation.
Ramp function: CPAP function that starts at a low pressure (often 4 cmH₂O) and gradually rises to therapeutic pressure during sleep onset (15-30 minutes). Greatly facilitates adaptation.
SpO2 (oxygen saturation): Non-invasive measurement of blood oxygen saturation via a finger pulse oximeter. Normal value: 95-100%. Repeated drops during sleep indicate significant nocturnal hypoxia.
STOP-BANG: 8-question Yes/No sleep apnea screening questionnaire (Snoring, Tired, Observed, Pressure, BMI, Age, Neck, Gender). Score ≥ 3: intermediate risk. Score ≥ 5: high risk.
Titration: An in-center sleep study to determine optimal CPAP pressure. The patient sleeps with CPAP while a technician adjusts pressure in real time to eliminate all apneas. Required for the INAMI convention.

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