ICU Literature Updates from May 2013

Characterisation of Sleep in Intensive Care Using 24-hour Polysomnography: An Observational Study

The goal of this study was to evaluate the sleep of intensive care patients with specific regards to environmental noise. 57 patients who were in an Australian tertiary hospital’s ICU were enrolled in this study. Polysomnography was performed over a 24 hour period to assess sleep. Noise and light levels were measures as well. The authors found that the majority of sleep was stage 1 and stage 2 sleep with very little slow wave and REM sleep. Most patients reported their sleep as poor. The authors concluded that sleep in the ICU is poor and may be related to noise, critical illness and treatment interactions.

Does Using Pressure-Controlled Ventilation to Rest Respiratory Muscles Improve Sleep in ICU Patients?

The authors of this study sought to evaluate the impact of pressure controlled ventilation compared to spontaneous ventilation. 35 patients with acute on chronic respiratory failure requiring mechanical ventilation were enrolled in this study. Sleep architecture was evaluated in a randomized cross-over design with patients being assigned to one mode from 10pm to 2 am and then the other mode from 2 am to 6am. The authors discovered that sleep architecture was altered in these patients. According to this study, PCV was associated with improved sleep quality and quantity compared to low PSV. The authors recommend that nocturnal respiratory muscles rest through PCV to improve sleep in the ICU.

Patient-Ventilator Synchrony and Sleep Quality with Proportional Assist and Pressure Support Ventilation

In this study, the authors examined patient ventilator asynchrony and sleep quality in fourteen critically ill patients who were not sedated. Approximately 86% of the patients had COPD as the reason fro admission to the ICU. Patients in this study were ventilated with either proportional assist ventilation with load adjustable gain factors (PAC+) or pressure support in a randomized crossover study design. During the evaluation, patients were placed on PSV or PAV+ and then alternated every 4 hours over night. Initial patient selection was based on patients asynchrony with PSV. Polysomnopgraphy was performed in these patients over 24 hours.

The authors found that PAV+ significantly reduced the number of asynchronies per hour when compared to PSV. However, PAV+ was also associated with more sleep fragmentation. The authors concluded that PAV+ improved asynchronies but failed to improve sleep in mechanically ventilated patients.

Comparison of Sleep Quality With Mechanical Versus Spontaneous Ventilation During Weaning of Critically Ill Tracheostomized Patients

In this study, the authors evaluated the impact of mechanical ventilation on sleep quality and quantity in patients who could not be liberated from mechanical ventilation and had a trach. The trial was a randomized cross over study, which enrolled 16 patients. All patients enrolled were free from sedation and were able tolerate at least 5 hours of spontaneous ventilation. Patients were randomized to spontaneous ventilation or low level of pressure support in a crossover fashion from 10pm to 8 AM. The authors found total sleep time to be greater in the mechanical ventilation group. There were no differences in slow wave sleep, REM sleep of the sleep fragmentation index in the groups. The authors concluded that sleep quality was not significantly different in difficult to wean patients with or without mechanical ventilation.