Effects of an additional pressure support level on exercise duration in patients on prolonged mechanical ventilation

Background/Purpose: Noninvasive positive pressure ventilation has been regarded as a strategy for improving exercise performance. Whether an increase in the ventilatory support level improves exercise performance in patients who have received invasive ventilation is unknown. The purpose of this study is to examine the effects of an additional level of pressure support (PS) ventilation on exercise tolerance in patients undergoing prolonged mechanical ventilation (PMV). Methods: This study examined 15 patients who were undergoing PMV. All patients performed an upper-arm exercise test at three PS levels: the baseline PS level (PS), a level 2 cmH₂O higher than the baseline level (PS+2), and a level 4 cmH₂O higher than the baseline level (PS+4). The physiological response, reasons for discontinuing the exercise test, and exercise duration were recorded and analyzed. Results: The tidal volume increased significantly from 271.7 ± 54.7 mL to 398.3 ± 88.7 mL at the PS+4 level (. p = 0.01). Significant differences in exercise duration were observed at different PS levels. The exercise duration was significantly longer at the PS+4 level than at the PS and PS+2 levels (146.3 ± 139.9 seconds vs. 108.5 ± 85.9 seconds vs. 72.8 ± 43.9 seconds, p = 0.038) as their corresponding order. There were significant relationships between resting respiratory rate and exercise duration at the PS (r = -0.639, p = 0.034) and PS+2 levels (r = -0.668, p = 0.025). Conclusion: In patients undergoing PMV, an additional PS level of up to 4 cmH₂O compared with the baseline setting may help to improve exercise tolerance by prolonging exercise duration.