• Bhushan H Katira, Doreen Engelberts, Sheena Bouch, Jordan Fliss, Luca Bastia, Kohei Osada, Kim A Connelly, AmatoMarcelo B PMBPLaboratório de Pneumologia LIM-09, Disciplina de Pneumologia, Instituto do Coração (Incor) Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil., Niall D Ferguson, Wolfgang M Kuebler, Brian P Kavanagh, Laurent J Brochard, and Martin Post.
• Translational Medicine Program, Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, 686 Bay St., 9th Floor, Toronto, ON, M5G 0A4, Canada.
• Crit Care. 2022 Feb 18; 26 (1): 4747.

BackgroundAn abrupt lung deflation in rodents results in lung injury through vascular mechanisms. Ventilator disconnections during endo-tracheal suctioning in humans often cause cardio-respiratory instability. Whether repeated disconnections or lung deflations cause lung injury or oedema is not known and was tested here in a porcine large animal model.MethodsYorkshire pigs (~ 12 weeks) were studied in three series. First, we compared PEEP abruptly deflated from 26 cmH2O or from PEEP 5 cmH2O to zero. Second, pigs were randomly crossed over to receive rapid versus gradual PEEP removal from 20 cmH2O. Third, pigs with relative volume overload, were ventilated with PEEP 15 cmH2O and randomized to repeated ETT disconnections (15 s every 15 min) or no disconnection for 3 h. Hemodynamics, pulmonary variables were monitored, and lung histology and bronchoalveolar lavage studied.ResultsAs compared to PEEP 5 cmH2O, abrupt deflation from PEEP 26 cmH2O increased PVR, lowered oxygenation, and increased lung wet-to-dry ratio. From PEEP 20 cmH2O, gradual versus abrupt deflation mitigated the changes in oxygenation and vascular resistance. From PEEP 15, repeated disconnections in presence of fluid loading led to reduced compliance, lower oxygenation, higher pulmonary artery pressure, higher lung wet-to-dry ratio, higher lung injury score and increased oedema on morphometry, compared to no disconnects.ConclusionSingle abrupt deflation from high PEEP, and repeated short deflations from moderate PEEP cause pulmonary oedema, impaired oxygenation, and increased PVR, in this large animal model, thus replicating our previous finding from rodents. Rapid deflation may thus be a clinically relevant cause of impaired lung function, which may be attenuated by gradual pressure release.© 2022. The Author(s).

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