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Unlabelled: Little is known about sleep/wake abnormalities in intensive care and less is known about the mechanisms responsible for these abnormalities. We studied 22 (20 mechanically ventilated) medical intensive care unit (ICU) patients with continuous polysomnography (PSG) and environmental noise measurements for 24-48 h to characterize sleep-wake patterns and objectively determine the effect of environmental noise on sleep disruption. All 22 patients demonstrated sleep-wake cycle abnormalities. There were large variations in total sleep time (TST) with the mean total sleep time per 24-h study period of 8.8 +/- 5.0 h. Sleep-wake cycles were fragmented and nonconsolidated with a mean of 57 +/- 18% and 43 +/- 18% of the TST occurring during the day and night, respectively. Environmental noise was responsible for 11.5 and 17% of the overall arousals and awakenings from sleep, respectively. The mean noise arousal index was 1.9 +/- 2.1 arousals/h sleep., Conclusions: (1) ICU patients are qualitatively, but not necessarily quantitatively, sleep deprived; and (2) although environmental noise is in part responsible for sleep-wake abnormalities, it is not responsible for the majority of the sleep fragmentation and may therefore not be as disruptive to sleep as the previous literature suggests.

The etiology of sleep disruption in patients in intensive care units (ICUs) is poorly understood, but is thought to be related to environmental stimuli, especially noise. We sampled 203 patients (121 males and 82 females) from different ICUs (cardiac [CCU], cardiac stepdown [CICU], medical [MICU], and surgical [SICU]) by questionnaire on the day of their discharge from the unit, to determine the perceived effect of environmental stimuli on sleep disturbances in the ICU. Perceived ICU sleep quality was significantly poorer than baseline sleep at home (p = 0.0001). Perceived sleep quality and daytime sleepiness did not change over the course of the patients' stays in the ICU, nor were there any significant differences (p > 0.05) in these parameters among respective units. Disruption from human interventions and diagnostic testing were perceived to be as disruptive to sleep as was environmental noise. In general, patients in the MICU appeared to be more susceptible to sleep disruptions from environmental factors than patients in the other ICUs. Our data show that: (1) poor sleep quality and daytime sleepiness are problems common to all types of ICUs, and affect a broad spectrum of patients; and (2) the environmental etiologies of sleep disruption in the ICU are multifactorial.