Consequences of vascular flow on lung injury induced by mechanical ventilation

To investigate whether the magnitude of blood flow contributes to ventilator-induced lung injury, 14 sets of isolated rabbit lungs were randomized for perfusion at either 300 (Group A: n = 7) or 900 ml/min (Group B: n = 7) while ventilated with 30 cm H₂O peak static pressure. Control lungs (Group C: n = 7) were ventilated with lower peak static pressure (15 cm H₂O) and perfused at 500 ml/min. Weight gain, changes in the ultrafiltration coefficient (ΔK_f) and lung static compliance (CL), and extent of hemorrhage (scored by histology) were compared. Group B had a larger decrease in CL (-13 ± 11%) than Groups A (2 ± 6%) and C (5 ± 5%) (p < 0.05). Group B had more hemorrhage and gained more weight (16.2 ± 9.5 g) than Groups A (8.7 ± 3.4 g) and C (1.6 ± 1.0 g) (p < 0.05 for each pairwise comparison between groups). Finally, K_f (g · min^-1 · cm H₂O^-1 · 100 g^-1) increased the most in Group B (ΔK_f = 0.26 ± 0.20 versus 0.17 ± 0.10 in Group A and 0.05 ± 0.04 in Group C; p < 0.05 for B versus C). We conclude that the intensity of lung perfusion contributes to ventilator-induced lung injury in this model.