Desaturation (Oxygen Desaturation)

An oxygen desaturation is a measurable drop in blood oxygen saturation (SpO2) from a baseline level. In sleep medicine, desaturations are typically measured at 3% (more sensitive) or 4% (more specific, aligned with AASM hypopnea scoring) thresholds from a 2-minute rolling baseline.

Desaturations occur when a breathing event, whether an apnea, hypopnea, or significant flow limitation, reduces the amount of oxygen reaching the lungs. The oxygen drop typically lags the breathing event by 20 to 40 seconds due to the circulatory transit time from lungs to the pulse oximeter on the finger or wrist.

The clinical significance of desaturations depends on their depth, duration, and frequency. Brief, shallow desaturations (3-4% drops) are less concerning than deep, prolonged drops (below 85% or lasting over 30 seconds). AirwayLab tracks both ODI-3 and ODI-4 (desaturation events per hour) and time below thresholds (T<90%, T<94%) to provide a complete picture of oxygen impact.