Abstract

Introduction: Novel markers of prognosis in the acute respiratory distress syndrome (ARDS) are needed. Hypothesis: We hypothesized that pulmonary vascular compliance would predict outcome in ARDS, and that higher left heart filling pressure would be associated with increased pulsatile loading of the right ventricle manifested as reduced RC time. Methods: We performed a retrospective analysis of 392 subjects with a complete hemodynamic data set on trial day 0 in the ARDS Network Fluid and Catheter Treatment Trial of PA catheter use in ARDS. Pulmonary vascular compliance (Cpa) was calculated as stroke volume divided by PA pulse pressure. Pulmonary vascular resistance (PVR) was calculated as mean PA pressure minus pulmonary artery wedge pressure (PAWP) divided by cardiac output. The RC time was calculated as the product of PVR and Cpa. Cox proportional hazard modeling and Kaplan-Meier survival analysis were performed with primary outcome of death. Results: The mean age was 50 ± 16 years. Mean PA pressure and PAWP were both elevated (29 ± 8 mmHg and 15 ± 5 mmHg, respectively) as was cardiac output (7.7 ± 2.7 L/m). The mean PVR was 2.1 ± 1.2 Wood units and Cpa 4.6 ± 2.5 ml/mmHg. Mean RC time was 0.47 ± 0.24 seconds (s). With each 5 mmHg increase in PAWP, RC time decreased by 0.06 s (p<0.0001 for slope). There was increased hazard of death per quartile decrease in Cp (HR 1.28, 95% CI 1.08-1.52; p = 0.004) and per quartile increase in PVR (HR 1.23, 95% CI 1.04-1.46; p = 0.02). Adjusted for APACHE III score, there remained a trend towards increased hazard of death per quartile increase in PVR (HR 1.2 95% CI 1.03-1.4, p = 0.02) and per quartile decrease in Cp (HR 1.18 95% CI 1.0-1.4, p = 0.055). Kaplan-Meier survival curves per quartile of Cp are shown in the Figure. Conclusion: Pulmonary vascular compliance predicts mortality in ARDS. Higher wedge pressure is associated with lower RC time in ARDS consistent with increased RV pulsatile loading.