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; FIO2, 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.