BACKGROUND
Experimentally, maintaining high pressure or high volume ventilation in animal models produces an acute lung injury, however, there was little information on remodeling. We investigated the collagen synthesis in a rat model of ventilator-induced lung injury.
METHODS
Rats were ventilated with room air at 85 breaths/minute for 2 hours either tidal volume 7 ml/kg or 20 ml/kg (V(T)7 or V(T)20, respectively). After 2 hours of ventilation, rats were placed in the chamber for 24 hours.
Lung collagen was evaluated by immunohistochemistry (n=5) and collagen was quantitated by collagen assay (n=5). Static compliance (Csta) of the whole lung as obtained from the pressure volume curves.
RESULTS
Type I collagen was an increase in expression in the interstitium with large V(T) (20 ml/ kg) ventilation after 2 hours of mechanical ventilation (MV), and further increased expression after 24 hours of recovery period.
Static lung compliance was significantly (p<0.05) decreased in the V(T)20 compared with V(T)7 (0.221+/-0.05 vs 0.305+/-0.06 ml/cm H2O) after 2 hours of MV. There was a further decrease in lung compliance after 24 hours of recovery period (0.144+/-0.07 vs 0.221+/-0.05, p<0.05) in the V(T)20.
CONCLUSIONS
Large tidal volume ventilation causes an increase in type 1 collagen expression with reduction of lung compliance.