Effect of prone-position ventilation on oxygenation in patients with acute respiratory distress syndrome

Objective To determine the effect of prone position (PP) ventilation on oxygenation in patients with acute respiratory distress syndrome (ARDS) .Methods Twenty-three patients of both sexes (14 males, 9 females) with ARDS (within 72 h after onset of ARDS) were included in this study. The patients ranged in age from 43-78 years. Ten minutes before the patients were placed in prone position, midazolam 2-5 mg was given i. v. followed by continuous infusion at 2-3 mg·h-1 for sedation and a bolus of vecuronium 4 mg per hour for muscle relaxation. The patients were mechanically ventilated (VT 6-8 ml·kg-1, inspiration-time 1.0-1.2 s, RR 12-20 bpm, FiO2 0.4-1.0, PEEP 6-18 cm H2O) . The patients were placed in prone position for 2 h. Radial artery was cannulated and S-G catheter placed. MAP, CVP, MPAP, PAWP, cardiac output, PaO2 , PaCO2 peak inspiratory pressure (PIP) and airway resistance (Raw) were measured and recorded immediately before (T0) and 0.5, 2 h after the patients were placed in prone position (T1 , T2) and 2 h after supine position was resumed(T3) . PaO2/FiO2 and static compliance of the respiratory system (Cst) were calculated. Results In 87% of the patients PaO2/FiO2 was significantly increased during prone position (T1, T2) as compared to the baseline (T0) (P 0.01) and remained high at T3 , but there was no significant change in Cst, HR, MAP, CVP, MPAP, Raw, PAWP,and CO at T1 and T2 as compared to the baseline at T0. In the 87% of the patients with inprovement in PaO2 /FiO2 , Cst did not change significantly at T1 and T2 but significantly increased at T3 ( P 0.05). Conclusion Prone position ventilation can improve pulmonary gas exchange in patients with early ARDS even after supine position is resumed.