Slow moderate pressure recruitment maneuver minimizes negative circulatory and lung mechanic side effects: Evaluation of recruitment maneuvers using electric impedance tomography

Objective: To evaluate the efficacy of different lung recruitment maneuvers using electric impedance tomography. Design and setting: Experimental study in animal model of acute lung injury in an animal research laboratory. Subjects: Fourteen pigs with saline lavage induced lung injury. Interventions: Lung volume, regional ventilation distribution, gas exchange, and hemodynamics were monitored during three different recruitment procedures: (a) vital capacity maneuver to an inspiratory pressure of 40 cmH₂O (ViCM), (b) pressure-controlled recruitment maneuver with peak pressure 40 and PEEP 20 cmH₂O, both maneuvers repeated three times for 30 s (PCRM), and (c) a slow recruitment with PEEP elevation to 15 cmH₂O with end inspiratory pauses for 7 s twice per minute over 15 min (SLRM). Measurements and results: Improvement in lung volume, compliance, and gas exchange were similar in all three procedures 15 min after recruitment. Ventilation in dorsal regions of the lungs increased by 60% as a result of increased regional compliance. During PCRM compliance decreased by 50% in the ventral region. Cardiac output decreased by 63±4% during ViCM, 44±2% during PCRM, and 21±3% during SLRM. Conclusions: In a lavage model of acute lung injury alveolar recruitment can be achieved with a slow lower pressure recruitment maneuver with less circulatory depression and negative lung mechanic side effects than with higher pressure recruitment maneuvers. With electric impedance tomography it was possible to monitor lung volume changes continuously.