Sleep

Critically ill patients are more likely to successfully weaned from a mechanical ventilator or breathing machine if they have higher levels of wakefulness and both their right and left brains experience the same depth of sleep, according to new research published online. In “Sleep and Pathological Wakefulness at Time of Liberation from Mechanical Ventilation,” Laurent Brochard, MD, Ph.D., and co-authors used polysomnography or a sleep study, and a novel index developed by one of the co-authors, Magdy Younes, MD, Ph.D.

The odds ratio product

The index’s odds ratio product (ORP) provides a continuous digital score from 0 (very deep sleep) to 2.5 (full wakefulness). While mechanical ventilation is life-saving; it can cause lung damage, infections; other health problems; patients should take off a ventilator as soon as medically possible. Physicians use a spontaneous breathing trial (SBT) during which a patient breathes with no or little help from the ventilator to assess the patient’s readiness for breathing on his or her own.
Therefore, “Successful separation from mechanical ventilation necessitates an adequate response from a number of physiological systems; all of which could impair by sleep deprivation. Noting that previous studies have, in fact; linked pathological sleep with prolonged difficulties in separated from the ventilator. “They wondered whether assessing a period of sleep and wakefulness in the hours before attempting a separation from the ventilator could predict the success of this process.

Toronto-area hospitals

” The researchers analyzed data from 37 patients at 3 Toronto-area hospitals who scheduled for an SBT and had undergone polysomnography for 15 hours before the test. SBT was successful in 19 patients. In 11 of these patients, their breathing tube is removed; in the other 8 patients; so the breathing tube is not removed because despite a successful SBT; other clinical factors indicated they were not ready for extubation. In 18 patients; the SBT was unsuccessful.
1. Therefore the classical sleep stages as by conventional sleep scoring guidelines not associated with the success or failure of the SBT.
2. Longer durations of full wakefulness as measured by ORP (>2.2) were highly correlated with a successful SBT and extubation.
3. Poor correlation between sleep depth in the right and left-brain hemispheres strongly predicts SBT failure.
The researchers said the fact that ORP scores with success or failure in weaning patients from mechanical ventilation while standard sleep scores were not; most likely reflects ORP’s ability to better distinguish different levels of sleep. Dr. Brochard explained that classical sleep analysis is very difficult by frequent “atypical” or “pathological” tracings in ICU patients. This is particularly true during a condition called pathological wakefulness.

Wakefulness or sleep classically

“Defining wakefulness or sleep classically, Dr. Brochard; necessitates detecting short-wave brain activity that typically characterizes sleep and a decrease in higher frequencies that characterize wakefulness and comparing these results to clinical behavior: does the patient look awake or asleep?” The researchers noted that sleep deprivation produces a brainwave pattern similar to pathological wakefulness and that despite being clinically awake patients are obtunded; meaning they are not fully awake.

The authors speculate that this pathological wakefulness is the flip side of sleep deprivation. So the dissociation between the brain hemispheres was an “entirely new” finding that raised many questions: What is exactly causing the dissociation between the two hemispheres observed in these patients? Is it primarily sleep deprivation? Or is there an influence of the sedative drugs.

In conclusion, Administered in the first days; or of certain medical conditions? How and how fast can it be reversed? Answers to these questions may lead to changes in how mechanically ventilated patients are managed in the ICU. “They now have a monitoring tool of the brain that can help us address questions of major importance for the outcome of patients in the ICU.