Complement activation contributes to ventilator-induced lung injury in rats

The complement system contributes to ventilator induced lung injury (VILI). We hypothesized that pretreatment with the C1 esterase inhibitor (C1INH) Berinert® constrains complement activation consecutively inducing improvements in arterial oxygenation and histological pulmonary damage. At baseline, male Sprague-Dawley rats underwent mechanical ventilation in a conventional mode (PIP 13 cm H₂O, PEEP 3 cm H₂O). In the Control group, the ventilator setting was maintained (Control, n = 15). The other animals randomly received intravenous pretreatment with either 100 units/kg of the C1-INH Berinert® (VILI-C1INH group, n = 15) or 1 ml saline solution (VILI-C group, n = 15). VILI was induced by invasive ventilation (PIP 35 cm H₂O, PEEP 0 cm H₂O). After two hours of mechanical ventilation, the complement component C3a remained low in the Control group (258 ± 82 ng/ml) but increased in both VILI groups (VILI-C: 1017 ± 283 ng/ml; VILIC1INH: 817 ± 293 ng/ml; P < 0.05 for both VILI groups versus Control). VILI caused a profound deterioration of arterial oxygen tension (VILI-C: 193 ± 167 mmHg; VILI/C1-INH: 154 ± 115 mmHg), whereas arterial oxygen tension remained unaltered in the Control group (569 ± 26 mmHg; P < 0.05 versus both VILI groups). Histological investigation revealed prominent overdistension and interstitial edema in both VILI groups compared to the Control group. C3a plasma level in the VILI group were inversely correlated with arterial oxygen tension (R = -0.734; P < 0.001). We conclude that in our animal model of VILI the complement system was activated in parallel with the impairment in arterial oxygenation and that pretreatment with 100 units/kg Berinert® did neither prevent systemic complement activation nor lung injury.