Sleep architecture in a canine model of obstructive sleep apnea

Obstructive sleep apnea (OSA) causes recurrent sleep disruption that is tho ught to contribute to excessive daytime sleepiness in patients with this di sorder. The purpose of this study was to determine the specific effects of OSA on overall sleep architecture in a canine model of OSA. The advantage o f this model is that sleep during long-term OSA can be compared to both nor mal sleep before OSA and recovery sleep after OSA. Studies were performed i n four dogs in which sleep-wake state was monitored continuously by a compu ter that received telemetered EEG and EMG signals. Whenever sleep was detec ted, the computer sent a signal to close a valve through which the dog brea thed; when the dog awoke the occlusion was released. In each dog, data were analyzed from 4 consecutive nights in three phases: a control phase before induction of OSA, a phase during long-term OSA (mean = 85 days, apnea inde x = 59/hour), and a recovery phase after cessation of OSA. During recovery there was a significant increase in the amount of rapid-eye-movement (REM) sleep compared to the OSA phase (p<0.01), as well as significant increases in sleep efficiency and decreases in wakefulness (p<0.01), similar to that reported in OSA patients. The REM rebound during recovery, however, could n ot be attributed to overall REM deprivation since the amount of REM sleep d uring the OSA phase was not different from the control phase (p=0.708). Thi s finding suggests that REM rebound during recovery from OSA is not the res ult of an overall REM sleep deficit per se. Rather, repeated sleep disrupti on due to the effects of repetitive apneas and hypoxia may lead to an incre ased REM sleep drive that manifests itself as a REM sleep rebound during re covery sleep after OSA.