Diffuse alveolar damage due to inappropriate strategy of mechanical ventilation in an experimental porcine model.

BACKGROUND The aim of the study was to determine how tidal volumes may affect the lung and haemodynamics during mechanical ventilation. MATERIALS AND METHODS With the approval of the Ethics Committee, the study included a total of 24 healthy piglets, average weight 30 kg (range 28-33 kg). The animals were ventilated for 90 minutes under general anaesthesia with two different tidal volume strategies and allocated into three groups. Group A, animals were healthy controls, Group B, animals comprised 8 piglets with an abdominal aortic aneurysm and ventilated with a low tidal volume strategy (VT(exp) 7 ml/kg). Group C comprised 8 animals seven days after kidney transplantation, ventilated with a high tidal volume strategy (VT(exp) 12 ml/kg). Changes in lung mechanics and hemodynamics were assessed at 30th and 90th minutes. Lung tissue samples were examined histologically. RESULTS Protective ventilation in Group A and B did not confer any haemodynamic and lung mechanic differences. Significant differences were only found in Group C at 90 minutes for increased preload of both heart ventricles (CVP; t-test 4.07, p<0.01 and PAoP; t-test 8.43, p<0.01), pulmonary vascular resistance (t-test 3.11, p<0.05), and decreased expiratory tidal volume (t-test 6.07, p<0.01), dynamic lung compliance (t-test 3.83, p<0.01) and cardiac output (t-test 2.07, p<0.01). Diffuse alveolar damage was detected histologically. CONCLUSION Mechanical ventilation at high tidal volumes reaching 12 ml/kg caused functional changes in the lungs, diffuse alveolar damage and reduction of cardiac output within 90 minutes.