ABSTRACT
Neil S. Freedman, Joost Gazendam, Lachelle Levan, Allan I. Pack, And
Richard J. Schwab
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 theoverall 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. (Am
J Respir Crit Care Med Vol 163. pp 451–457, 2001)
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