Partial liquid ventilation and positive end-expiratory pressure reduce ventilator-induced lung injury in an ovine model of acute respiratory failure

Objective: To examine the isolated and combined effects of positive end-expiratory pressure (PEEP) and partial liquid ventilation (PLV) on the development of ventilator-induced lung injury in an ovine model. Design: Prospective controlled animal study. Setting: University-based cardiovascular animal physiology laboratory. Subjects: Thirty-eight anesthetized supine sheep weighing 22.3 ± 2.2 kg. Interventions: Animals were ventilated for 6 hrs (respiratory rate, 15; F10₂, 1.0, inspiratory/expiratory ratio, 1:1) with one of five pressure-controlled strategies, expressed as peak inspiratory pressure (PIP)/PEEP: low-PIP, 25/5 cm H₂O (n = 8); high-PIP, 50/5 cm H₂O (n = 8); high-PIP-PLV, 50/5 cm H₂O-PLV (n = 8); high-PEEP, 50/20 cm H₂O (n = 7); and high-PEEP-PLV, 50/20 cm H₂O-PLV (n = 7). Measurements and Main Results: Compared with the low-PIP control, high-PIP ventilation increased airleak, shunt, histologic evidence of lung injury, neutrophil infiltrates, and wet lung weight. Maintaining PEEP at 20 cm H₂O or adding PLV reduced the development of physiologic shunt and dependent histologic injury indexes. Neither higher PEEP nor PLV reduced the high incidence of barotrauma observed in high-PIP animals. Conclusions: We conclude that application of PLV or PEEP at 20 cm H₂O may improve gas exchange and afford lung protection from ventilator-induced lung injury during high-pressure mechanical ventilation in this model.