Lung morphology predicts response to recruitment maneuver in patients with acute respiratory distress syndrome

Abstract

Objectives: The impact of recruitment maneuvers on gas exchange, hemodynamics, alveolar recruitment, and hyperinflation is highly variable among patients with acute respiratory distress syndrome. The objective was to determine whether differences in lung morphology, defined as differences in the pulmonary distribution of aeration loss, predict the response to recruitment maneuvers.

Design: Prospective study.

Setting: A 16-bed medical-surgical intensive care unit in a university hospital.

Measurements and main results: Nineteen consecutive patients with early acute lung injury/acute respiratory distress syndrome were studied. Computed tomography scans, respiratory mechanics, hemodynamics, and gas exchange were obtained at zero end-expiratory pressure during an open-lung ventilation (controlled mode, tidal volume 6 mL/kg of ideal body weight, positive end-expiratory pressure set 2 cm H2O above the lower inflection point of the inspiratory pressure volume curve at zero end-expiratory pressure) during a recruitment maneuver (continuous positive airway pressure of 40 cm H2O for 40 secs), and, finally, 5 mins after the recruitment maneuver during open-lung ventilation. Nine patients presented focal and 10 presented nonfocal lung morphology at zero end-expiratory pressure. Recruitment maneuver-induced recruited volume after 5 mins of open-lung ventilation was 48 +/- 66 mL and 417 +/- 293 mL in patients with focal and nonfocal lung morphology, respectively (p = .0009). Recruitment maneuver-induced alveolar hyperinflation represented 23% +/- 14% and 8% +/- 9% of total lung volume in patients with focal and nonfocal morphology, respectively (p = .007). In patients with focal lung morphology, hyperinflated lung volume was significantly greater during and 5 mins after (316 +/- 155 mL) than immediately before recruitment maneuvers (150 +/- 175 mL; p = .0407.

Conclusion: Lung morphology at zero end-expiratory pressure predicts the response to recruitment maneuvers. Patients with focal lung morphology are at risk for significant hyperinflation during the recruitment maneuvers, and lung recruitment is rather limited.