Gender is shown to have little objective effect on polysomnography sleep architecture or sleep regulation. Women (age > 50 years) may have slightly better SWS preservation than men. Power spectral analysis has shown a small increase in delta, theta, and lower a frequencies in women compared with men… Normative data during illness will be needed to establish whether the increase in delta activity in these patients reflects cerebral dysfunction. Certainly in the IS group who were fully awake, alert, and responsive with minimal drug influence, cerebral dysfunction is less likely an etiology of increased delta activity. Source
Our study had several limitations. The sample size was too small to allow for logistic regression, and several factors may confound the results. Because the study was underpowered, negative findings must be interpreted cautiously. The wide SD reflected the large variability in the groups and results could have been affected by one or two subjects. Blood drug levels were not drawn so we are unable to evaluate the actual drug level, dosage, and stages of sleep between groups. IL-1 and TNF levels also were not obtained, so a clear determination of the effect of sepsis is unknown. Although we sought to control for extraneous variables by limiting our patient population to only medical ICU patients with respiratory diagnoses, patients were not randomized and the groups differed in type of respiratory diagnosis and gender distribution. This could have led to a preselection bias based on the preexistence of the medication regimen alone. Finally, normative sleep data during illness is lacking.
This study suggests that 24-h continuous monitoring of sleep, an unrecognized vital sign, may be helpful in critically ill patients. Although patients receiving NMBA were sedated, they were shown to be awake by EEG criteria approximately 22% of the time. The functional significance of this is unknown. Circadian rhythm was disturbed, and daytime sleep periods were essential to prevent total sleep deprivation. TST increased as severity of illness increased. All patients demonstrated fragmented sleep and increased amounts of delta activity using the traditional Rechtschaffen and Kales amplitude criteria and a modified 50-^V criteria. The patients receiving NMBA demonstrated a nonstatistically significant 5% increase in delta activity using the mDelta criteria. The cause of fragmented sleep and increased delta is likely multifactorial and may be due to variation in methodology, age, drugs, metabolic effects related to illness, and the homeostatic effect on delta activity. Further studies are needed to delineate the independent contribution of these factors in a larger sample of critically ill patients. Use of a power spectral approach for analyzing sleep and sedation may be more sensitive in detecting changes in a and delta activity. Whether sleep disruption contributes to difficulty with weaning from mechanical ventilation and recovery from illness needs to be determined. Promoting sleep consolidation may facilitate this process.