Improving the Sleep and Circadian Rhythms of Mechanically Ventilated Patients

The goal of this project is to determine whether the sleep and circadian rhythms of critically ill patients undergoing mechanical ventilation can be improved through practical strategies that can be employed at the bedside.

Nearly 1 million patients develop respiratory failure annually in the United States; yet, the sleep of patients undergoing mechanical ventilation has received little attention. This project is designed to characterize sleep and circadian rhythmicity in critically ill patients and to explore the efficacy of a non-pharmacological intervention to improve sleep and normalize circadian phase. The study will examine the effect of a protocol employing noise reduction and enforcement of a robust light-dark cycle on sleep quality and circadian rhythmicity. A secondary analysis will examine the relationship between delirium and sleep disruption and loss of circadian rhythmicity. Circadian rhythmicity will be characterized through the measurement of urinary 6-sulfatoxymelatonin levels at frequent intervals, while sleep will be assessed using continuous polysomnography.

This multifaceted intervention attempts to enhance sleep and circadian rhythmicity through improved scheduling of nursing procedures, enforcement of a day/night routine, increased light exposure during the day, and decreased light and sound exposure during the night. The intervention began the morning after enrollment and enforced a specific period of enhanced light exposure from 9:00 a.m. to noon. The initial target of 5,000 lux administered by light box (Sunsation, SunBox Co.) was reduced to 400-700 lux after the first 10 subjects were enrolled in the study.

The magnitude of the phase change in 6-sulfatoxymelatonin excretion between Day 1 and Day 3 will be compared between the intervention and usual care groups. This is done by comparing, for each group, the timing of the best-fit maximum on Day 1 with the timing of the best-fit maximum on Day 3. The result is expressed in hours. A positive value represents a phase advance from Day 1 to Day 3 (e.g. an earlier occurrence of maximum excretion on Day 3 when compared with Day 1), while a negative value represents a phase delay from Day 1 to Day 3 (e.g. a later occurrence of maximum excretion on Day 3 when compared with Day 1).

The percentage of subjects who exhibit normal circadian timing of 6-sulfatoxymelatonin excretion on Day 3 will be compared between the intervention and usual care groups.

The amplitude (e.g. one half the value from peak to trough of the fitted cosine curve) of the circadian rhythm of 6-sulfatoxymelatonin on Day 3 will be compared between the usual care and intervention groups.

The difference between the polysomnographically derived daytime and nocturnal spectral edge frequency 95% parameter will be used as a measure of increased diurnal sleep/wake activity. This parameter will be compared between the usual care and intervention groups.

The percentage of patients who are delirious at the conclusion at the study will be compared between the intervention and usual care groups.

Inclusion Criteria: Age 18 years or older Receiving mechanical ventilation and intravenous sedation Exclusion Criteria: Debilitating central nervous system disease or degenerative disorder Active seizures Persistent coma Renal failure requiring dialysis Expected to be extubated within 24 hours Currently receiving neuromuscular blocker