Efficacy of Different Recruitment Maneuvers for Improved Lung Inhomogeneity in a Pig Model of ARDS

Background: In acute respiratory distress syndrome (ARDS), lung recruitment maneuvers can recruit collapsed alveoli in gravity-dependent lung regions, improving the homogeneity of ventilation distribution. This study used electrical impedance tomography (EIT) to investigate the efficacy of different recruitment maneuvers for alveolar recruitment in a pig model of ARDS. Methods: ARDS was induced in ten healthy male pigs with repeated bronchoalveolar lavage until the arterial partial pressure of oxygen (PaO 2 )/fraction of inspired oxygen (FiO 2 ) (P/F ratio) was < 100 mmHg and remained stable for 30 minutes (TARDS). ARDS pigs underwent three sequential recruitment maneuvers, including sustained inflation (SI), increments of positive end-expiratory pressure (PEEP) (IP), and pressure-controlled ventilation (PCV) applied in random order, with 30 mins at a PEEP of 5 cmH 2 O between maneuvers. Respiratory mechanics, hemodynamics, arterial blood gas, and EIT were recorded at baseline, TARDS, and before and after each recruitment maneuver.Results: In all ten pigs, ARDS was successfully induced with a mean 2.8±1.03 (2800±1032.80ml) bronchoalveolar lavages. PaO 2 , SO 2 , P/F, and compliance were significantly improved after recruitment with SI, IP or PCV (all p<0.05), and there were no significant differences between maneuvers. Global inhomogeneity (GI) was significantly decreased after recruitment with SI, IP, or PCV. There were no significant differences in GI before or after recruitment with the different maneuvers. The decrease in GI (ΔGI) was significantly greater after recruitment with IP compared to SI (p=0.023), but there was no significant difference in ΔGI between IP and PCV. Conclusion: SI, IP, and PCV increased oxygenation, regional compliance and lung compliance, and decreased inhomogeneous gas distribution with no adverse effects on hemodynamics in ARDS pigs. IP significantly improved inhomogeneity of the lung compared to SI.