Lung computed tomography during a lung recruitment maneuver in patients with acute lung injury

Abstract

Objective: To assess the acute effect of a lung recruitment maneuver (LRM) on lung morphology in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Patients: Ten patients with ALI/ARDS on mechanical ventilation. Design: Prospective clinical study. Setting: Computed tomography (CT) scan facility in a teaching hospital. Interventions: An LRM performed by stepwise increases in positive end-expiratory pressure (PEEP) of up to 30–40 cmH2O. Lung basal CT sections were taken at end-expiration (patients 1 to 5), and at end-expiration and end-inspiration (patients 6 to10). Arterial blood gases and static compliance (Cst) were measured before, during and after the LRM. Measurements and main results: Poorly aerated and non-aerated tissue at PEEP 10 cmH2O accounted for 60.0±29.1% of lung parenchyma, while only 1.1±1.8% was hyperinflated. Increasing PEEP to 20 and 30 cmH2O, compared to PEEP 10 cmH2O, decreased poorly aerated and non-aerated tissue by 16.2±28.0% and 33.4±13.8%, respectively (p<0.05). This was associated with an increase in PaO2 and a decrease in total static compliance. Inspiration increased alveolar recruitment at all PEEP levels. Hyperinflated tissue increased up to 2.9±4.0% with PEEP 30 cmH2O, and to a lesser degree with inspiration. No barotrauma or severe hypotension occurred. Conclusions: Lung recruitment maneuvers improve oxygenation by expanding collapsed alveoli without inducing too much hyperinflation in ALI/ARDS patients. An LRM during the CT scan gives morphologic and functional information that could be useful in setting ventilatory parameters.