Sleep is considered restorative and important for illness recovery. In converse, sleep disruption has been shown to adversely affect recovery from illness by reducing cognition, immune function, respiratory drive and cardiovascular function. Yet, the sleep of critically ill patients has received little attention, despite the clinical importance and possibility of reducing mortality. Dr. Brian Gehlbach recognized this need of investigation of sleep disruption in critically ill patients undergoing mechanical ventilation, and will utilize the Brain Research Foundation Seed Grant to elucidate the correlation between sleep quality and clinical outcomes.
The experience of critical care encompasses a variety of stimuli and interventions that may interfere with normal sleep. The physical environment of a hospital room has been shown to be poorly suited for normal sleep. Constant background noise levels that frequently range between 60 and 80 dB and ambient light that frequently is not in phase with the patients’ normal light/dark cycle can interfere with a patient’s “internal body clock” or circadian rhythms. In addition, procedures and nursing care are generally performed without consideration of the time of day which can also disrupt sleep. Finally, the critical illness itself may disturb sleep through the experiences of pain, fear or central nervous system disturbance.
While a handful of studies have demonstrated circadian rhythm disturbances in patients on ventilators, the infrequent sampling of hormone levels to determine rhythmicity and the absence of concurrent polysomnography (sleep recording) have left a lot of unanswered questions. Dr. Gehlbach plans to definitively characterize the circadian rhythms and quality of sleep of acutely ill patients undergoing mechanical ventilation for respiratory failure.
The first aspect of the project will characterize the sleep quality and circadian rhythms of critically ill patients on a ventilator. All patients in the study will undergo continuous polysomnography to determine sleep quality. It is expected that most patients will exhibit reduced and fragmented REM sleep patterns. In addition, the levels of 6-sulfatoxymelatonin (the major metabolite of the pineal hormone melatonin) will be measured at hourly intervals in order to assess circadian rhythmicity, which is expected to be disrupted.
In addition to analyzing the patient’s sleep quality and circadian rhythm, Dr. Gehlbach and his colleagues will manipulate the hospital room environment to promote better sleep by reducing noise, enforcing a normal light-dark cycle, and if possible performing nursing care according to time of day. This management of the environment should strengthen circadian rhythms and improve sleep quality.
The ultimate outcome of this study is to speed up recovery and lessen the duration of mechanical ventilation. It has been shown that the presence of delirium has been associated with adverse clinical outcomes, including longer hospital stay and increased 6-month mortality for patients with respiratory failure. However, the role of sleep disruption in mediating delirium has not been investigated. If a relationship between disrupted sleep and delirium in critical illness is determined, doctors could utilize practical strategies that can be employed at the bedside to greatly impact a patient’s recuperation.
Dr. Gehlbach is confident that this previously neglected but extremely important area of research will generate results that are immediately applicable to the care of our sickest patients, and that something as simple as turning off the light at night may help save a life.