Severe Impairment in Lung Function Induced by High Peak Airway Pressure during Mechanical Ventilation

Abstract

We explored the pulmonary effects of continuous mechanical ventilation (MV) at a peak inspiratory pressure of 50 cm H2O in healthy, paralyzed, and anesthetized adult sheep during a period of 48 h. The 9 control sheep (Group A) were ventilated with 40% oxygen at a tidal volume of about 10 ml/kg and a peak inspiratory pressure of 15 to 20 cm H2O. All these animals remained stable throughout the 48 h of MV with no change in lung function. The 7 sheep in Group B were ventilated with 40% oxygen using a pressure-controlled ventilator at 50 cm H2O peak inspiratory pressure, at a Vt of 50 to 70 ml/kg. All sheep in Group B developed severe respiratory failure and died or were killed within 2 to 35 h, and showed parenchymal consolidation at autopsy. The 9 sheep in Group C were ventilated as in Group B, except that 3.8% CO2 was added to the inspired gases: the Group C animals deteriorated more slowly, with little change in PaO2 but with a severely reduced FRC, Vt, total static lung compliance, and grossly abnormal l...