Continuous long-term prone position ventilation effects in pulmonary acute respiratory distress syndrome patients

Introduction

The optimal duration of prone position ventilation (PPV) in acute respiratory distress syndrome (ARDS) is uncertain. It has been pointed out that pulmonary ARDS patients respond less than extrapulmonary ARDS patients.

Objective

To study effects of continuous long-term PPV on gas exchange, PEEP, lung injury score and multiorgan failure in pulmonary ARDS patients.

Materials and methods

The design was a prospective (cohort). We studied 42 PPV periods in 33 pulmonary ARDS patients. Measures were taken in the supine position before PPV and at 1 hour after PPV, and then every 6 hours until the end of PPV. Statistical values are expressed as the median and interquartile range. Wilcoxon and Kruskal–Wallis tests were used. P < 0.05 was considered significant.

Results

The mean age was 44 (25–57) years, the initial lung injury score (LIS) was 3.1 (2.75–3.6), and PPV was maintained for 91 (51–117) hours. The PaO₂/FIO₂ ratio was 125 (99–181) mmHg before PPV and 256 (170–298) mmHg after 1 hour of PPV (P = 0.001). This difference with the supine PaO₂/FIO₂ ratio was sustained until the end of PPV. Initial values of PEEP were set at 15 (12–18) cmH₂O by constructing a PEEP-compliance curve; there were no differences in PEEP values along the study. Initial values of PaCO₂ were 47 (41–69) mmHg and there were no significant differences along the study period. After 24 hours of PPV, the LIS was significantly decreased in comparison with the supine value before PPV: 3 (2.25–2.7) vs 2.5 (2.25–2.75), P = 0.001. There were no significant complications.

Conclusion

PPV had a positive effect on gas exchange even after 6 hours. This effect lasts through the PPV period. Because of its effect on the LIS, a duration of 24 hours for continuous PPV could be useful in this patient setting.