Measuring sleep in critically ill patients: beware the pitfalls.

Survivors of critical illness frequently report poor sleep while in the intensive care unit (ICU), and sleep deprivation has been hypothesized to lead to emotional distress, ICU delirium and neurocognitive dysfunction, prolongation of mechanical ventilation, and decreased immune function. Thus, the careful study of sleep in the ICU is essential to understanding possible relationships with adverse clinical outcomes. Such research, however, must be conducted using sleep measurement techniques that have important limitations in this unique setting. Polysomnography (PSG) is considered the gold standard but is cumbersome, time consuming, and expensive. As such, alternative methods of sleep measurement such as actigraphy, processed electroencephalography monitors, and subjective observation are often used. Though helpful in some instances, data obtained using these methods can often be inaccurate and misleading. Even PSG itself must be interpreted with caution in this population due to effects of critical illness and associated treatments.