Early trajectories of pulmonary hemodynamics in ARDS patients undergoing V-V ECMO: key determinants and prognostic impact

Background Pulmonary hypertension (PH) frequently complicates acute respiratory distress syndrome (ARDS) and contributes to right ventricular dysfunction and mortality. Veno-venous extracorporeal membrane oxygenation (V-V ECMO) may attenuate PH through improved gas exchange, yet pulmonary pressures often remain elevated. Data on the determinants and prognostic impact of PH in ECMO-supported ARDS are limited. Methods We performed a retrospective observational study of adult ARDS patients receiving V-V ECMO at a tertiary referral center between 2003 and 2024. Only patients monitored with a pulmonary artery catheter were included. Daily hemodynamic, ventilatory, and gas exchange data were prospectively collected. Determinants of mean pulmonary artery pressure (mPAP) were analyzed using a linear mixed-effects model. The association of (1) mPAP on the first day of ECMO and (2) the mPAP trajectory over the first 5 ECMO days—expressed as the patient-specific daily slope—with hospital mortality was assessed using logistic regression before and after adjustment for confounders. Results Among 240 consecutive V-V ECMO patients, 225 had a pulmonary artery catheter and were analyzed. Median age was 51 years, 33% were female. The median mPAP during ECMO was 27 mmHg [23–32], with 91% of measurements exceeding 20 mmHg. Independent determinants of higher mPAP included intrapulmonary shunt fraction, lower venous pH, higher pulmonary artery occlusion pressure, increased PEEP, reduced respiratory system compliance, and longer ECMO duration. In contrast, higher venous partial pressure of oxygen and mixed venous oxygen saturation were associated with lower mPAP. mPAP on the first day of ECMO was not associated with hospital mortality. In contrast, the trajectory of mPAP during the first 5 days was independently associated with mortality (adjusted OR 1.89 per 1-mmHg/day increase, 95% CI 1.33–2.77, p < 0.001). Conclusions Pulmonary hypertension is highly prevalent in ARDS patients on V-V ECMO and reflects underlying disease severity. Early upward trajectories in mPAP, rather than the initial mPAP value, independently predicted higher mortality. Serial pulmonary pressure monitoring may provide relevant prognostic information and help guide management of pulmonary hemodynamics in ECMO-supported ARDS.