Positive End-Expiratory Pressure and Respiratory Rate Modify the Association of Mechanical Power and Driving Pressure With Mortality Among Patients With Acute Respiratory Distress Syndrome

IMPORTANCE: Mechanical power and driving pressure have known associations with survival for patients with acute respiratory distress syndrome. OBJECTIVES: To further understand the relative importance of mechanical power and driving pressure as clinical targets for ventilator management. DESIGN: Secondary observational analysis of randomized clinical trial data. SETTING AND PARTICIPANTS: Patients with the acute respiratory distress syndrome from three Acute Respiratory Distress Syndrome Network trials. MAIN OUTCOMES AND MEASURES: After adjusting for patient severity in a multivariate Cox proportional hazards model, we examined the relative association of driving pressure and mechanical power with hospital mortality. Among 2,410 patients, the relationship between driving pressure and mechanical power with mortality was modified by respiratory rate, positive end-expiratory pressure, and flow. RESULTS: Among patients with low respiratory rate (< 26), only power was significantly associated with mortality (power [hazard ratio, 1.82; 95% CI, 1.41–2.35; p < 0.001] vs driving pressure [hazard ratio, 1.01; 95% CI, 0.84–1.21; p = 0.95]), while among patients with high respiratory rate, neither was associated with mortality. Both power and driving pressure were associated with mortality at high airway flow (power [hazard ratio, 1.28; 95% CI, 1.15–1.43; p < 0.001] vs driving pressure [hazard ratio, 1.15; 95% CI, 1.01–1.30; p = 0.041]) and neither at low flow. At low positive end-expiratory pressure, neither was associated with mortality, whereas at high positive end-expiratory pressure (≥ 10 cm H(2)O), only power was significantly associated with mortality (power [hazard ratio, 1.22; 95% CI, 1.09–1.37; p < 0.001] vs driving pressure [hazard ratio, 1.16; 95% CI, 0.99–1.35; p = 0.059]). CONCLUSIONS AND RELEVANCE: The relationship between mechanical power and driving pressure with mortality differed within severity subgroups defined by positive end-expiratory pressure, respiratory rate, and airway flow.