Lung Volume Recruitment after Surfactant Administration Modifies Spatial Distribution of Ventilation

Abstract

Although surfactant replacement therapy is an established treatment in infant respiratory distress syndrome, the optimum strategy for ventilatory management before, during, and after surfactant instillation remains to be elucidated. To determine the effects of surfactant and lung volume recruitment on the distribution of regional lung ventilation. Acute lung injury was induced in 16 newborn piglets by endotracheal lavage. Optimum positive end-expiratory pressure was identified after lung recruitment and surfactant was administered either at this pressure in the "open" lung or after disconnection of the endotracheal tube in the "closed" lung. An additional recruitment maneuver with subsequent optimum end-expiratory pressure finding was executed in eight animals; in the remaining eight animals, end-expiratory pressure was set at the same level as before surfactant without further recruitment. ("Open" and "closed" lung surfactant administration was evenly distributed in the groups.) Regional ventilation was assessed by electrical impedance tomography. Impedance tomography data, airway pressure, flow, and arterial blood gases were acquired during baseline conditions, after induction of lung injury, after the first lung recruitment, and before as well as 10 and 60 min after surfactant administration. Significant shift in ventilation toward the dependent lung regions and less asymmetry in the right-to-left lung ventilation distribution occurred in the postsurfactant period when an additional recruitment maneuver was performed. Surfactant instillation in an "open" versus "closed" lung did not influence ventilation distribution in a major way. The spatial distribution of ventilation in the lavaged lung is modified by a recruitment maneuver performed after surfactant administration.