Objective: To examine patient-ventilator asynchrony and sleep quality in non-sedated critically ill patients ventilated with proportional assist ventilation with load adjustable gain factors (PAV+) and pressure support (PSV).
Methods: This was a randomized crossover physiological study conducted in an adult ICU at a tertiary hospital. Patients who exhibited patient-ventilator asynchrony on PSV were selected. Polysomnography was performed in these patients over 24 h, during which respiratory variables were continuously recorded. During the study period, each patient was randomized to receive alternating 4-h periods of PSV and PAV+ equally distributed during the day and night. Sleep architecture was analyzed manually using predetermined criteria. Patient-ventilator asynchrony was evaluated breath by breath using the flow-time and airway pressure-time waveforms.
Results: Fourteen patients were studied. The majority (85.7 %) had either acute exacerbation of COPD as admission diagnosis or COPD as comorbidity. During sleep, compared to PSV, PAV+ significantly reduced the patient-ventilator asynchrony events per hour of sleep [5 (1-17) vs. 40 (4-443), p = 0.02, median (25-75th interquartile range)]. Compared to PSV, PAV+ was associated with slightly but significantly greater sleep fragmentation [18.8 (13.1-33.1) versus 18.1 (7.0-22.8) events/h, p = 0.01] and less REM sleep [0.0 % (0.0-8.4) vs. 5.8 % (0.0-21.9), p = 0.02).
Conclusions: PAV+ failed to improve sleep in mechanically ventilated patients despite the fact that this mode was associated with better synchrony between the patient and ventilator. These results do not support the hypothesis that patient-ventilator synchrony plays a central role in determining sleep quality in this group of patients.