Bedside Estimate of Mechanical Power (Part 5): Mortality Risk in ARDS Comparing Predictive Thresholds for Plateau Pressure, Driving Pressure, and Mechanical Power

Background: Previous abstract (Part 4) compared mechanical power transferred to the respiratory system (WRS), in which below/above the 20 J/min threshold revealed a widening mortality departure (ie, 24% vs. 42% respectively). Those whose WRS > 20 J/min accounted for 65% of subjects. Thresholds in plateau pressure (Pplat) > 30 cm H2O and driving pressure (PDR) > 15 cm H2O are also associated with increasing mortality risk in ARDS.1,2 This study examined the relevance of all three thresholds on mortality risk when compared to prominent non-pulmonary factors that drive mortality in ARDS.3 Methods: 948 ARDS subjects previously described (abstracts part 1-4) had threshold values for WRS, Pplat and PDR compared to non-pulmonary factors (ie, age, ARDSNet study comorbidity exclusion criteria,1 and APACHE II scores) both in univariate and multivariate logistic regression modeling. Alpha was set at 0.05. Results: In univariate analyses all variables were associated with mortality risk (P < .001). Low collinearity was found between dichotomous expressions of the inter-related variables WRS, Pplat and PDR (R2:0.19, 0.19, 0.23 respectively). Multivariate modelling revealed Pplat and WRS thresholds, but not PDR threshold, remained strongly associated with mortality when controlled for non-pulmonary variables (Table). Area under receiver operative curve of 0.80 (95%CI: 0.77-0.83), P < .001. Conclusions: When lung protective ventilation is initiated ≤ 24 h after ARDS onset, exceeding Pplat and WRS thresholds influences mortality rather than PDR threshold > 15 cm H2O.1. ARDS Network. N Engl J Med 2000;342(18):1301. 2. Amato MB et al. N Engl J Med 2015;372(8):747. Kallet RH et al. Respir Care 2019;64(5):493.Table 1VariablesOdds Ratio (95%CI)PAge1.03 (1.02-1.04)<0.001ARDSNet Exclusion+2.52 (1.83-3.47)<0.001APACHE II*1.09 (1.06-1.11)<0.001Wrs > 20 J/m1.76 (1.22-2.56)0.003Pplat > 30 cmH2O3.16 (1.92-5.25)<0.001Pdr > 15 cmH2O1.23 (0.86-1.76)0.25*APACHE = acute physiology and chronic health evaluation