Interview by Sree Roy
Mechanical ventilation can be a necessary supportive treatment for patients with breathing difficulties, with successful weaning often the goal. How can clinicians better predict who will pass or fail ventilation weaning?
A new study reports that patients in a long-term acute care facility being weaned from prolonged ventilation exhibited atypical sleep electroencephalogram (EEG) patterns linked with weaning failure. Patients with atypical sleep EEG patterns had higher rates of subsyndromal delirium and slowing of the wakeful EEG, suggesting these as biological signals for brain dysfunction.
“Pharmacologic and nonpharmacologic therapy may promote sleep consolidation and lower the incidence of delirium in critically ill patients. Whether these interventions to promote sleep consolidation can facilitate the return to normal sleep and wake EEG patterns, and their impact on outcomes, is unknown,” says study first author Hameeda Shaikh, MD, an assistant professor of medicine at Loyola University Stritch School of Medicine and director of the pulmonary and sleep outpatient clinics at Edward J Hines VA Hospital.
Shaikh discussed the study with Sleep Review over email. The transcript has been lightly edited for clarity and style.
[Editor’s Note: Read the full study, Effect of atypical-sleep EEG patterns on weaning from prolonged mechanical ventilation, in CHEST.]
What is the clinical significance of the study’s findings?
Brain dysfunction, as evidenced by the biologic signal of atypical sleep, persisted in patients at a long-term acute care facility, far beyond the onset of the initial critical illness in the acute intensive care unit (ICU), and was associated with weaning failure. This indicates that brain dysfunction, demonstrated by atypical sleep and wakeful EEG, may be an important factor in the pathogenesis of failure to wean from mechanical ventilation.
What challenges did you experience in performing full polysomnography (Natus Sandman Elite) on the patients in these studies that you likely wouldn’t have experienced in healthy people?
Performing sleep studies in patients on invasive mechanical ventilation was challenging at times. The patients in our study were unable to phonate, as they were ventilated via tracheostomy tube connected to a ventilator. Any perceived patient discomfort or irritation had to be patiently and carefully assessed by the investigator obtaining the sleep study. Nursing care, with frequent repositioning of the patient, often resulted in lead displacement. This issue was best addressed by having the investigator be present in the room to assist with patient repositioning.
Knowing what you know now about the study results, would you have changed anything about the equipment used to measure sleep in these circumstances?
Identifying atypical sleep can be challenging, and obtaining the full sleep EEG montage ensured that the interpreting investigators had ample EEG channels on which to base the analysis. We also used the respiratory inductive plethysmography bands and ventilator pressure and flow signals to evaluate for sleep disruption caused by respiratory-related arousals.
Obtaining the full night of data was also informative in that we could determine that REM sleep was less prominent in patients with atypical sleep compared to those with usual sleep. This finding allowed us to speculate on a possible mechanistic link between atypical sleep and weaning failure, as selective REM sleep deprivation is associated with a hypermetabolic state and total body catabolism. These observations suggest potential mechanisms whereby respiratory muscle structure and function are affected by atypical sleep.
Power spectral analysis was performed on a brief period of wakefulness, and atypical sleep patients demonstrated slowing of the wakeful EEG and higher rates of weaning failure. Whether slowing of the wakeful EEG alone (without sleep EEG data) could discriminate patients with weaning failure from those with successful weaning at a long-term acute care center is an interesting question for future research.
In the future, wireless EEG devices may improve the ease of obtaining sleep studies in the ICU and long-term acute care hospitals.
The findings support the possibility of a mechanistic link between the reticular activating system and atypical sleep. Can you further explain this?
Cognition was impaired—as evidenced by the presence of subsyndromal delirium—and there was slowing of the wakeful EEG in patients with atypical sleep. As the reticular activating system is the central regulatory center for sleep-wake transition, as well as cortical alertness and attention, we propose that the development of atypical sleep may be related to dysfunction at the level of the reticular activating system.
Further Reading:
What Does the Sleeping Brain Do in the ICU?
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