Hypopnea

A hypopnea is a partial reduction in airflow lasting at least 10 seconds, associated with either an oxygen desaturation of 3 to 4% or a cortical arousal. Unlike an apnea (complete or near-complete airflow cessation), a hypopnea represents partial airway obstruction where some airflow continues but at a significantly reduced level.

Hypopneas are counted in the AHI alongside apneas and are often more common than complete apneas, especially on PAP therapy where the air pressure prevents full collapse but may not fully prevent partial narrowing. The scoring criteria for hypopneas have changed over the years, leading to inconsistencies between different sleep labs and machines.

On PAP therapy, residual hypopneas may indicate the pressure is insufficient to fully prevent airway narrowing during certain sleep stages or positions. AirwayLab can detect hypopneas from flow amplitude drops when EVE.edf event files are not present, or it uses the machine's own event counts from EVE.edf when available, since the machine has access to internal algorithms that cannot be replicated from flow data alone.