Obstructive Sleep Apnea Measurements

Obstructive sleep apnea leads to partial reductions (hypopneas) and complete pauses (apneas) in breathing that last at least 10 seconds during sleep. Most pauses last between 10 and 30 seconds, but some may persist for one minute or longer. This can lead to abrupt reductions in blood oxygen saturation, with oxygen levels falling as much as 40 percent or more in severe cases.

The brain responds to the lack of oxygen by alerting the body, causing a brief arousal from sleep that restores normal breathing. This pattern can occur hundreds of times in one night.

How is the Severity of Obstructive Sleep Apnea Assessed?

The Respiratory Disturbance Index (RDI) records respiratory events, but unlike the AHI, includes respiratory event-related arousals (RERAs).

RERAs are arousals from sleep that do not technically meet the definitions of apneas or hypopneas but disrupt sleep.

A sleep apnea patient is diagnosed by a sleep test conducted in a sleep center or verified by a home sleep test. Each patient is evaluated by an assessment of multiple factors.