Study objectives: To evaluate the effect of body position on REM-related obstructive sleep apnea (OSA) patients.
Design: Retrospective analysis.
Patients: 100 consecutive adult OSA patients (apnea-hypopnea index [AHI] > or = 5) who had > or = 10 min of REM sleep in both supine and lateral postures. REM-related OSA was defined by previously used criteria (REM AHI/Non-REM (NREM) AHI > or = 2) and was compared with data from Not-REM-related OSA (REM AHI/NREM AHI < 2).
Measurements and results: Most (93%) of the REM-related OSA patients (n = 45) had a mild-moderate syndrome, compared to 50.9% in the Not-REM-related OSA patients (n = 55). REM-related OSA patients had a lower apnea index (AL), AHI, supine and lateral AHI, and NREM AHI, but similar REM AHI compared to the Not-REM-related OSA group. For the entire group, the following sequence was observed: AHI REM supine > AHI NREM supine > AHI REM lateral > AHI NREM lateral. Also, for the REM-related and Not-REM-related OSA patients, the interaction between supine posture and REM sleep led to the highest AHI. However, the average length of apnea and hypopneas during REM sleep was similar in the supine and lateral postures.
Conclusions: During REM sleep, the supine position is associated with increased frequency but not increased duration of apneas and hypopneas. These body position effects prevail over the differences between REM-related and Not-REM-related OSA patients.