UC San Diego

Copyright © 2015 by the Society of Criti. Objective: Global lung stress varies considerably with low tidal volume ventilation for acute respiratory distress syndrome. High stress despite low tidal volumes may worsen lung injury and increase risk of death. No widely available parameter exists to assess global lung stress. We aimed to determine whether the volume delivered during a recruitment maneuver (VRM) is inversely associated with lung stress and mortality in acute respiratory distress syndrome. Design: Substudy of an acute respiratory distress syndrome clinical trial on esophageal pressure-guided positive end-expiratory pressure titration. Setting: U.S. academic medical center. Patients: Forty-two patients with acute respiratory distress syndrome in whom airflow, airway pressure, and esophageal pressure were recorded during the recruitment maneuver. Interventions: A single recruitment maneuver was performed before initiating protocol-directed ventilator management. Recruitment maneuvers consisted of a 30-second breath hold at 40 cm H2O airway pressure under heavy sedation or paralysis. VRM was calculated by integrating the flow-time waveform during the maneuver. End-inspiratory stress was defined as the transpulmonary (airway minus esophageal) pressure during end-inspiratory pause of a tidal breath and tidal stress as the transpulmonary pressure difference between end-inspiratory and end-expiratory pauses. Measurements and Main Results: VRM ranged between 7.4 and 34.7 mL/kg predicted body weight. Lower VRM predicted high end-inspiratory and tidal lung stress (end-inspiratory: β = -0.449; 95% CI, -0.664 to -0.234; p < 0.001; tidal: β = -0.267; 95% CI, -0.423 to -0.111; p = 0.001). After adjusting for Pao2/Fio2 and either driving pressure, tidal volume, or plateau pressure and positive end-expiratory pressure, VRM remained independently associated with both end-inspiratory and tidal stress. In unadjusted analysis, low VRM predicted increased risk of death (odds ratio, 0.85; 95% CI, 0.72-1.00; p = 0.026). VRM remained significantly associated with mortality after adjusting for study arm (odds ratio, 0.84; 95% CI, 0.71-1.00; p = 0.022). Conclusions: Low VRM independently predicts high lung stress and may predict risk of death in patients with acute respiratory distress syndrome.