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Continuous negative abdominal pressure reduces ventilator-induced lung injury in a porcine model - 12/7/2018

Anesthesiology 2018; 121: 163-72


In 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'.



 The authors carried out a randomised laboratory study in anaesthetised pigs. Lung injury was induced by surfactant lavage followed by 1?hour of injurious mechanical ventilation. Randomisation (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?hours 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 (versus ˜3) cm H2O in the PEEP (versus PEEP plus continuous negative abdominal pressure) groups. Oesophageal pressure, haemodynamics and electrical impedance tomography were recorded, and injury determined by lung wet/dry weight ratio and interleukin-6 expression.


All animals survived but cardiac output was decreased in the PEEP group. The addition of continuous negative abdominal pressure to PEEP resulted in greater oxygenation (PaO2/fractional inspired oxygen 316?±?134 versus 80?±?24 mmHg at 4?hours; p=0.005), compliance (14.2?±?3.0 versus 10.3?±?2.2?ml/cm H2O; p=0.049) and homogeneity of ventilation, with less pulmonary oedema (˜10% less) and interleukin-6 expression (˜30% less).



The authors conclude that continuous 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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