Assessment of sleep in ventilator-supported critically ill patients

Abstract

Objectives: In critically ill patients, sleep derangements are reported to be severe using Rechtschaffen and Kales (R&K) methodology; however, whether such methodology can reliably assess sleep during critical illness is unknown. We set out to determine the reproducibility of 4 different sleep-assessment methods (3 manual and 1 computer-based) for ventilator-supported critically ill patients and also to quantify the extent to which the reproducibility of the manual methods for measuring sleep differed between critically ill and ambulatory (control) patients. Design: Observational methodologic study. Setting: Academic center. Patients: Critically ill patients receiving mechanical ventilation and age-matched controls underwent polysomnography. Interventions: None. Measurements and Results: Reproducibility for the computer-based method (spectral analysis of electroencephalography [EEG]) was better than that for the manual methods: R&K methodology and sleep-wakefulness organization pattern (P = 0.03). In critically ill patients, the proportion of misclassifications for measurements using spectral analysis, sleep-wakefulness organization pattern, and R&K methodology were 0%, 36%, and 53%, respectively (P < 0.0001). The EEG pattern of burst suppression was not observed. Interobserver and intraobserver reliability of the manual sleep-assessment methods for critically ill patients (K = 0.52 ± 0.23) was worse than that for control patients (K = 0.89 ± 0.13; P = 0.03). In critically ill patients, the overall reliability of the R&K methodology was relatively low for assessing sleep (K = 0.19), but detection of rapid eye movement sleep revealed good agreement (K = 0.70). Conclusions: Reproducibility for spectral analysis of EEG was better than that for the manual methods: R&K methodology and sleep-wakefulness organization pattern. For assessment of sleep in critically ill patients, the use of spectral analysis, sleep-wakefulness organization state, or rapid eye movement sleep alone may be preferred over the R&K methodology.