Oxygenation versus driving pressure for determining the best positive end-expiratory pressure in acute respiratory distress syndrome

OBJECTIVE: The aim of this prospective longitudinal study was to compare driving pressure and absolute PaO(2)/FiO(2) ratio in determining the best positive end-expiratory pressure (PEEP) level. PATIENTS AND METHODS: In 122 patients with acute respiratory distress syndrome, PEEP was increased until plateau pressure reached 30 cmH(2)O at constant tidal volume, then decreased at 15-min intervals, to 15, 10, and 5 cmH(2)O. The best PEEP by PaO(2)/FiO(2) ratio (PEEP(O2)) was defined as the highest PaO(2)/FiO(2) ratio obtained, and the best PEEP by driving pressure (PEEP(DP)) as the lowest driving pressure. The difference between the best PEEP levels was compared to a non-inferiority margin of 1.5 cmH(2)O. MAIN RESULTS: The best mean PEEP(O2) value was 11.9 ± 4.7 cmH(2)O compared to 10.6 ± 4.1 cmH(2)O for the best PEEP(DP): mean difference = 1.3 cmH(2)O (95% confidence interval [95% CI], 0.4–2.3; one-tailed P value, 0.36). Only 46 PEEP levels were the same with the two methods (37.7%; 95% CI 29.6–46.5). PEEP level was ≥ 15 cmH(2)O in 61 (50%) patients with PEEP(O2) and 39 (32%) patients with PEEP(DP) (P = 0.001). CONCLUSION: Depending on the method chosen, the best PEEP level varies. The best PEEP(DP) level is lower than the best PEEP(O2) level. Computing driving pressure is simple, faster and less invasive than measuring PaO(2). However, our results do not demonstrate that one method deserves preference over the other in terms of patient outcome. Clinical trial number: #ACTRN12618000554268. Registered 13 April 2018.