Intercomparison of recruitment maneuver efficacy in three models of acute lung injury

Objective: To compare the relative efficacy of three forms of recruitment maneuvers in diverse models of acute long injury characterized by differing pathoanatomy. Design: We compared three recruiting maneuver (RM) techniques at three levels of post-RM positive end-expiratory pressure in three distinct porcine models of acute lung injury: oleic acid injury; injury induced purely by the mechanical stress of hightidal airway pressures; and pneumococcal pneumonia. Setting: Laboratory in a clinical research facility. Subjects: Twenty-eight anesthetized mixed-breed pigs (23.8 ± 2.6 kg). Interventions: The RM techniques tested were sustained inflation, extended sigh or incremental positive end-expiratory pressure, and pressure-controlled ventilation. Primary Measurements: Oxygenation and end-expiratory lung volume. Main Results: The post-RM positive end-expiratory pressure level was the major determinant of post-maneuver Pao₂, independent of the RM technique. The pressure-controlled ventilation RM caused a lasting increase of Pao ₂ in the ventilator-induced lung injury model, but in oleic acid injury and pneumococcal pneumonia, there were no sustained oxygenation differences for any RM technique (sustained inflation, incremental positive end-expiratory pressure, or pressure-controlled ventilation) that differed from raising positive end-expiratory pressure without RM. Conclusions: Recruitment by pressure-controlled ventilation is equivalent or superior to sustained inflation, with the same peak pressure in all tested models of acute lung injury, despite its lower mean airway pressure and reduced risk for hemodynamic compromise. Although RM may improve Pao₂ in certain injury settings when traditional tidal volumes are used, sustained improvement depends on the post-RM positive end-expiratory pressure value.