Sleep medicine reviews
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Upper airway obstruction is common during both anaesthesia and sleep, as a result of loss of muscle tone present during wakefulness. Patients with obstructive sleep apnoea (OSA) are vulnerable during anaesthesia and sedation as the effects of loss of wakefulness are compounded by drug-induced depression of muscle activity and of arousal responses, so that they cannot respond to asphyxia. ⋯ On the one hand identification of patients with OSA forewarns the anaesthetist of potential difficulty with airway maintenance intra- and postoperatively, influencing choice of anaesthetic technique and postoperative nursing environment. On the other hand difficulty with airway maintenance during anaesthesia should prompt further investigation for the possibility of OSA.
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Sleep medicine reviews · Dec 2004
ReviewState transitions between wake and sleep, and within the ultradian cycle, with focus on the link to neuronal activity.
The structure of sleep across the night as expressed by the hypnogram, is characterised by repeated transitions between the different states of vigilance: wake, light and deep non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. This review is concerned with current knowledge on these state transitions, focusing primarily on those findings that allow the integration of data at cellular level with spectral time-course data at the encephalographic (EEG) level. At the cellular level it has been proposed that, under the influence of circadian and homeostatic factors, transitions between wake and sleep may be determined by mutually inhibitory interaction between sleep-active neurons in the hypothalamic preoptic area and wake-active neurons in multiple arousal centres. ⋯ And there is substantial evidence at cellular level that transition to and from REM sleep is governed by the reciprocal interaction between cholinergic REM-on neurons and aminergic REM-off neurons located in the brainstem. Similarity between the time-course of the REM-on neuronal activity and that of EEG power in the high beta range (approximately 18-30 Hz) allows a tentative parallelism to be drawn between the two. This review emphasises the importance of the thalamically projecting brainstem activating systems in the orchestration of the transitions that give rise to state progression across the sleep-wake cycle.