• Takeshi Yoshida, Doreen Engelberts, Gail Otulakowski, Bhushan Katira, Martin Post, Niall D Ferguson, Laurent Brochard, Amato Marcelo B P MBP, and Brian P Kavanagh.
• From the Department of Translational Medicine (T.Y., D.E., G.O., B.K., M.P., B.P.K.) Departments of Critical Care Medicine and Anesthesia (T.Y., B.K., B.P.K.), Hospital for Sick Children, University of Toronto, Toronto, Canada Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada (T.Y., B.K., N.F., L.B., B.P.K.) Division of Respirology, Department of Medicine, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada (N.F.) Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada (L.B.) the Cardio-Pulmonary Department, Pulmonary Division, Heart Institute (Incor), University of São Paulo, Brazil (M.A.).
• Anesthesiology. 2018 Jul 1; 129 (1): 163-172.

BackgroundIn supine patients with acute respiratory distress syndrome, the lung typically partitions into regions of dorsal atelectasis and ventral aeration ("baby lung"). Positive airway pressure is often used to recruit atelectasis, but often overinflates ventral (already aerated) regions. A novel approach to selective recruitment of dorsal atelectasis is by "continuous negative abdominal pressure."MethodsA randomized laboratory study was performed in anesthetized pigs. Lung injury was induced by surfactant lavage followed by 1 h of injurious mechanical ventilation. Randomization (five pigs in each group) was to positive end-expiratory pressure (PEEP) alone or PEEP with continuous negative abdominal pressure (-5 cm H2O via a plexiglass chamber enclosing hindlimbs, pelvis, and abdomen), followed by 4 h of injurious ventilation (high tidal volume, 20 ml/kg; low expiratory transpulmonary pressure, -3 cm H2O). The level of PEEP at the start was ≈7 (vs. ≈3) cm H2O in the PEEP (vs. PEEP plus continuous negative abdominal pressure) groups. Esophageal pressure, hemodynamics, and electrical impedance tomography were recorded, and injury determined by lung wet/dry weight ratio and interleukin-6 expression.ResultsAll animals survived, but cardiac output was decreased in the PEEP group. Addition of continuous negative abdominal pressure to PEEP resulted in greater oxygenation (PaO2/fractional inspired oxygen 316 ± 134 vs. 80 ± 24 mmHg at 4 h, P = 0.005), compliance (14.2 ± 3.0 vs. 10.3 ± 2.2 ml/cm H2O, P = 0.049), and homogeneity of ventilation, with less pulmonary edema (≈10% less) and interleukin-6 expression (≈30% less).ConclusionsContinuous negative abdominal pressure added to PEEP reduces ventilator-induced lung injury in a pig model compared with PEEP alone, despite targeting identical expiratory transpulmonary pressure.

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