Effect of earplugs on polysomnographic sleep and description of sleep-disturbing factors in critically ill subjects

Consequences of sleep deprivation in critically ill patients may include impaired lymphocyte and granulocyte function, reduction of natural killer cell and lymphokine-activated killer cell number and activity, and delayed weaning from mechanical ventilation. Studies of the impact of sleep-promoting interventions in mechanically ventilated subjects are not available. The primary objective of this research was to measure the impact of soft foam earplugs to reduce noise during the nighttime hours on the sleep of critically ill subjects. An increase in the sleep maintenance efficiency index (SMEI) and rapid eye movement (REM) sleep was expected when earplugs were worn. Other sleep disrupters and sleep during the day and afternoon hours were measured. Patients more than 18 years of age, who met the enrollment criteria, were studied using a randomized, unblinded, crossover design. Polysomnographic sleep was measured on 2 nights, with one "washout" night in between. Earplugs were randomly assigned to be worn on 1 night. A variety of environment, care content, and care process variables was also measured. Polysomnographic sleep was measured during the day and afternoon hours in 7 subjects. The sample consisted of 5 males and 8 females, with average ± SD for age = 56.9 ± 20 years, days in intensive care unit (ICU) at enrollment = 12.6 ± 8.3. Twelve of the subjects were mechanically ventilated. Significantly more REM sleep was obtained on the night earplugs were worn, and the power to detect a difference in SMEI was inadequate. All 13 subjects' sleep architecture was severely disturbed compared to normal sleep architecture, with or without earplugs. A clear pattern of increased opportunity for sleep on the night earplugs were worn was evident. Subjects slept during the day and afternoon hours; however, sleep architecture remained grossly fragmented, with markedly reduced REM and slow-wave sleep (SWS). The clinical significance of the increase in REM sleep seen in this study is open to debate. The study provides a reasonable basis to use earplugs to promote sleep because earplugs did provide more REM sleep. Over time, the effects might be of clinical importance. Before the efficacy of sleep in critically ill patients can be tested, an effective intervention must be developed.