Animal model of unilateral ventilator-induced lung injury

Objective: To design, implement, and test a selective lung ventilator for setting a rat model of unilateral ventilator-induced lung injury (VILI). Design and setting: Interventional animal study in a university laboratory for animal research. Subjects: Anesthetized and paralyzed male Wistar rats. Interventions: A selective ventilator designed to apply varying tidal volume, PEEP, and breathing gas to each lung of the rat was implemented and evaluated. Five control animals were ventilated at 7 ml/kg (3.5 ml/kg each lung). Unilateral VILI was induced in six animals subjected to selective ventilation (3.5 ml/kg in one lung and 15 ml/kg in the other lung). After 3 h of ventilation the animals were killed and the lungs excised. Measurements and results: Lung edema was assessed by means of the ratio between wet and dry lung weights. No significant differences were found in lungs of control animals (5.16 +/- 0.22 and 4.96 +/- 0.25), but the W/D ratio in the over ventilated lung (8.98 +/- 3.80) was significantly greater than that in the normally ventilated lung (4.76 +/- 0.15), indicating selective induction of lung edema by over stretch. Conclusions: This selective ventilator can be implemented into a rat model of unilateral VILI to gain further insight into the mechanisms of pulmonary injury induced by different ventilatory strategies.