[Sleep in intensive care: a crucial but little-known issue].

A CRUCIAL BUT LITTLE-KNOWN ISSUE. Polysomnography is the best tool to study sleep in intensive care unit (ICU), but this recording is complex to perform in such environment. Sleep alterations in ICU patients are specific and include electroencephalographic abnormalities during sleep and wake, rendering sleep scoring more complicated. Severe deficit in deep sleep, rapid eye movement sleep and an important sleep fragmentation are reported by most studies. Sleep cycles are disorganized with many sleep episodes during daytime. Sleep disruptions result from light levels, noisy environment, and 24-hours nurses care. Assisted ventilation, sedation, loss of circadian rhythms also contribute to these disruptions. Biological and neurobehavioral consequences of sleep alterations lengthen weaning from mechanical ventilation and have some deleterious impacts on morbidity and mortality. Procedures to promote sleep have been attempted, with limited results to date. However, recent innovation might help to monitor sleep and help patients to achieve some restorative sleep.