Contributions of vascular flow and pulmonary capillary pressure to ventilator-induced lung injury

Objective: To evaluate the influence of vascular flow on ventilator-induced lung injury independent of vascular pressures. Design: Laboratory study. Setting: Hospital laboratory. Subjects: Thirty-two New Zealand White rabbits. Interventions: Thirty-two isolated perfused rabbit lungs were allocated into four groups: low flow/low pulmonary capillary pressure; high flow/high pulmonary capillary pressure; low flow/ high pulmonary capillary pressure, and high flow/low pulmonary capillary pressure. All lungs were ventilated with peak airway pressure 30 cm H2O and positive end-expiratory pressure 5 cm H2O for 30 mins. Measurements and Main Results: Outcome measures included frequency of gross structural failure (pulmonary rupture), pulmonary hemorrhage, edema formation, changes in lung compliance, pulmonary vascular resistance, and pulmonary ultrafiltration coefficient. Lungs exposed to high pulmonary vascular flow ruptured more frequently, displayed more hemorrhage, developed more edema, suffered larger decreases in compliance, and had larger increases in vascular resistance than lungs exposed to low vascular flows (p < .05 for each pairwise comparison between groups). Conclusions: These findings suggest that high pulmonary vascular flows might exacerbate ventilator-induced lung injury independent of their effects on pulmonary vascular pressures. Copyright © 2006 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins.