Partition of respiratory mechanics in patients with acute respiratory distress syndrome and association with outcome: a multicentre clinical study.

Purpose: In acute respiratory distress syndrome (ARDS), physiological parameters associated with outcome may help defining targets for mechanical ventilation. This study aimed to address whether transpulmonary pressures (P), including transpulmonary driving pressure (DP), elastance-derived plateau P, and directly-measured end-expiratory P, are better associated with 60-day outcome than airway driving pressure (DP). We also tested the combination of oxygenation and stretch index [PaO/(FiO*DP)].

Methods: Prospective, observational, multicentre registry of ARDS patients. Respiratory mechanics were measured early after intubation at 6 kg/ml tidal volume. We compared the predictive power of the parameters for mortality at day-60 through receiver operating characteristic (ROC) and assessed their association with 60-day mortality through unadjusted and adjusted Cox regressions. Finally, each parameter was dichotomized, and Kaplan-Meier survival curves were compared.

Results: 385 patients were enrolled 2 [1-4] days from intubation (esophageal pressure and arterial blood gases in 302 and 318 patients). As continuous variables, DP, DP, and oxygenation stretch index were associated with 60-day mortality after adjustment for age and Sequential Organ Failure Assessment, whereas elastance-derived plateau P was not. DP and DP performed equally in ROC analysis (P = 0.0835). DP had the best-fit Cox regression model. When dichotomizing the variables, DP ≥ 15, DP ≥ 12, plateau P ≥ 24, and oxygenation stretch index < 10 exhibited lower 60-day survival probability. Directly measured end-expiratory P ≥ 0 was associated with better outcome in obese patients.

Conclusion: DP was equivalent predictor of outcome than DP. Our study supports the soundness of limiting lung and airway driving pressure and maintaining positive end-expiratory P in obese patients.