PAP reports use short labels to describe breathing patterns detected while the machine is running. The labels help a clinician investigate a trend, but the device does not collect all the signals used in a sleep laboratory. Check the report's glossary because definitions and available fields vary.
OA: obstructive apnea
This usually means the device detected a substantial pause in airflow and classified the airway as obstructed. In a sleep study, breathing-effort signals help establish whether someone is trying to breathe against a blockage. A home PAP machine normally infers the event from its own signals.
CA: central or clear-airway event
Some reports use CA for central apnea; others describe clear-airway events. The device may infer that the airway remained open during a pause. It does not directly prove that breathing effort was absent. Wakeful breath-holding, irregular breathing around sleep transitions and poor signals can complicate interpretation.
A new or persistent pattern warrants clinical review, especially with symptoms. It is not a reason to increase pressure yourself or diagnose central sleep apnea from an app.
H: hypopnea
A hypopnea is a qualifying reduction in breathing. Formal sleep-study scoring also considers oxygen desaturation or a brain arousal under the rule used. A device without these measurements uses its own detection method, so its H count is not interchangeable with a laboratory count.
FL: flow limitation
Flow limitation describes a breathing pattern that may suggest narrowing during inspiration. It may appear as a graph, index or flag. The scale is device-specific, and a flattened trace does not by itself prove a clinically important sleep disturbance.
RERA: respiratory effort-related arousal
In sleep-study scoring, a RERA is a breathing disturbance ending in an EEG-defined arousal that does not meet apnea or hypopnea criteria. A PAP device may flag a pattern thought to resemble this, but cannot directly establish the EEG arousal without that measurement.
Use the labels together
AHI usually combines apnea and hypopnea counts per hour; it does not simply add every label displayed on the report. Review the recording period, usage, leak and symptoms alongside the event breakdown. Bring an export or clear screenshot with dates and units so the clinician can see what the device actually reported.
Related reading: How AHI is calculated: events, hours and different reports