[Non-apneic respiratory arousal in obstructive sleep apnea syndrome]

Hypersomnia in obstructive sleep apnea syndrome (OSAS) is due to sleep fragmentation caused by arousals related to repeated episodes of apnea. Arousals may also be triggered by other non-apneic respiratory events (NAREs). The contribution of NARE to sleep disruption and nocturnal desaturation has been assessed by evaluating the polysomnograms of 58 consecutive OSAS patients. We studied 28 cases (25 men) presenting more than 5 NAREs/hour of sleep in addition to apneic events. Mean age was 48.8 +/- 14 years, mean body mass index was 38.1 +/- 10.2 kg/m2 and mean oxygen saturation at baseline, before the polysomnogram, was 94.0 +/- 2.5%. The following NARE categories were identified: incomplete apnea, paradoxical breathing, periodic breathing, hypoventilation and snore-arousals. All respiratory arousals were tabulated as indexes (number/hours of sleep). Although the number of apneic arousals was significantly greater, the NARE arousal index, both in REM and non-REM sleep reached the sleep disruption range (around 20 arousals/hour). Apneic desaturations were greater than non-apneic ones, during both REM and non-REM sleep. We conclude that NARE significantly contribute to sleep fragmentation in nearly half the patients with OSAS.