Sleep monitoring in the intensive care unit: comparison of nurse assessment, actigraphy and polysomnography.

OBJECTIVE: Sleep loss and sleep disruption are common in critically ill patients and may adversely affect clinical outcomes. Although polysomnography remains the most accurate and reliable way to measure sleep, it is costly and impractical for regular use in the intensive care unit. This study evaluates the accuracy of two other methods currently used for measuring sleep, actigraphy (monitoring of gross motor activity) and behavioural assessment by the bedside nurse, by comparing them to overnight polysomnography in critically ill patients. DESIGN: Observational study with simultaneous polysomnography, actigraphy and behavioural assessment of sleep. SETTING: Medical-surgical intensive care unit. PATIENTS AND PARTICIPANTS: Twelve stable, critically ill, mechanically ventilated patients [68 (13) years, Glasgow coma scale 11 (0)]. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Sleep was severely disrupted, reflected by decreased total sleep time and sleep efficiency, high frequency of arousals and awakenings and abnormal sleep architecture. Actigraphy overestimated total sleep time and sleep efficiency. The overall agreement between actigraphy and polysomnography was <65%. Nurse assessment underestimated the number of awakenings from sleep. Estimated total sleep time, sleep efficiency and number of awakenings by nurse assessment did not correlate with polysomnographic findings. CONCLUSIONS: Actigraphy and behavioural assessment by the bedside nurse are inaccurate and unreliable methods to monitor sleep in critically ill patients.

Contribution of the intensive care unit environment to sleep disruption in mechanically ventilated patients and healthy subjects.

Recent studies have challenged the traditional hypothesis that excessive environmental noise is central to the etiology of sleep disruption in the intensive care unit (ICU). We characterized potentially disruptive ICU noise stimuli and patient-care activities and determined their relative contributions to sleep disruption. Furthermore, we studied the effect of noise in isolation by placing healthy subjects in the ICU in both normal and noise-reduced locations. Seven mechanically ventilated patients and six healthy subjects were studied by continuous 24-hour polysomnography with time-synchronized environmental monitoring. Sound elevations occurred 36.5 +/- 20.1 times per hour of sleep and were responsible for 20.9 +/- 11.3% of total arousals and awakenings. Patient-care activities occurred 7.8 +/- 4.2 times per hour of sleep and were responsible for 7.1 +/- 4.4% of total arousals and awakenings. Healthy subjects slept relatively well in the typically loud ICU environment and experienced a quantitative, but not qualitative, improvement in sleep in a noise-reduced, single-patient ICU room. Our data indicate that noise and patient-care activities account for less than 30% of arousals and awakenings and suggest that other elements of the critically ill patient's environment or treatment should be investigated in the pathogenesis of ICU sleep disruption.