Effect of Dynamic Ventilatory Factors on Lung Histopathology in a Dog Model of Acute Respiratory Distress Syndrome

Objective To evaluate the effect of dynamic ventilatory factors on lung histopathology in a dog model of acute respiratory distress syndrome(ARDS).Methods The ARDS dog model was duplicated by instillation hydrochloric acid.The dogs were divided into 4 groups:(1) low VT(6 mL/kg) at respiratory rate 30,low inspiratory flow 6 mL/(kg·s).(2) large VT(20 mL/kg) at respiratory rate 30,high inspiratory flow 20 mL/(kg·s).(3) large VT(20 mL/kg) at respiratory rate 15,high inspiratory flow 17 mL/(kg·s).(4) large VT(20 mL/kg) at respiratory rate 15,low inspiratory flow 10 mL/(kg·s).All the dogs were killed after 4 h ventilation.Physiology parameters、lung histopathological changes、DAD scores、and PMN counting were measured.Results Under light microscope,lung tissue appeared seriously pathological changes in group B.Alveolar wall was obscure and dent without cavity.There were the infiltration of inflammatory cells and proteins and red blood cells.Alveolar septum became thick.DAD scores in group B(12.8 ±1.47) was higher than that in groups A and D(P0.01),there was no difference between groups B and C(P0.05).Conclusion Large volume ventilation with high inspiratory flow 、high respiratory rate could produce severe lung injury.Reduction of inspiratory flow and respiratory rate at large volume ventilation provides pulmonary protection.