Effect of prone position on the oxygenation of patients with acute respiratory distress syndrome after failure recruitment maneuvers at high altitudes

OBJECTIVE: To assess the effect of prone position on the oxygenation of patients with acute respiratory distress syndrome (ARDS) after recruitment maneuvers (RM) failure at high altitudes. METHODS: Forty-one ARDS patients who were invalid for RM therapy at the altitude of 2260 metres area hospital were enrolled[mean oxygenation index (PaO(2)/FiO(2)) increased than RM<20% considered as RM invalid]. All were divided into acute respiratory distress syndrome (ARDSp) and extra-acute respiratory distress syndrome (ARDSexp) based on different etiology, and each group was randomly divided into the supine and the prone position group, i.e. that ARDSp prone position group (n=11), ARDSp supine group (n=9), ARDSexp prone position group (n=10), and ARDSexp supine group (n=11). Before ventilation and 1, 2, 3, 4 hours after ventilation, arterial partial pressure of oxygen (PaO(2)), PaO(2)/FiO(2), static lung compliance (Cst), airway resistance (Raw) were monitored. RESULTS: One hour after ventilation in ARDSexp prone position group, PaO(2)/FiO(2) was significantly higher than before ventilation (157.4±40.6 mm Hg vs. 129.3±48.7 mm Hg, P<0.05), and increased by ventilation time, peaked at 4 hours (219.1±41.1 mm Hg). Within 3 hours ventilation in ARDSexp prone position group, PaO(2)/FiO(2) was significantly higher compared with the other three groups, and there were no significant differences among the other three groups. PaO(2)/FiO(2) in ARDSp prone position group and ARDSexp prone position group at 4 hours of ventilation were significantly higher compared with the corresponding supine group (208.8±39.7 mm Hg vs. 127.4±47.1 mm Hg, 219.1±41.1 mm Hg vs. 124.9±50.8 mm Hg, both P<0.05). There was no statistically significant difference in Cst before and after ventilation, and there was no significant changes among the groups. Raw in ARDSp prone position group at 4 hours of ventilation were significantly reduced than before ventilation (6.8±1.7 cm H(2)O×L(-1)×s(-1) vs. 10.7±1.8 cm H(2)O×L(-1)×s(-1), P<0.05), and significantly lower than the other three groups. There was no statistically significant difference in RAW among other three groups at each time point. CONCLUSION: Prone position can improve RM oxygenation invalid ARDS patients at high altitudes.