Effects of hypercapnia on oxygen free radicals in acute lung injury models / 中华急诊医学杂志

ABSTRACT

Objective To investigate the protective effects of hypereapnia on acute lung injury(ALI)in an model of rabbits in vivo,and to observe its effect on oxygen free radicals in the lung tissue in order to uncover the potential mechanisms.Method In the laboratory of pharmacology,China Medical Univereity,twenty-two healthy New Zealand white rabbits were randomly assigned to control group(Group C,n=6)with the injection of normal saline(0.1 ml/kg),and sixteen rabbits were injected with oleic acid(0.1ml/kg)intravenously,and then were randomly dirided into normocapnia group(Group N,n=8)and hypercapnia group(Group H,n=8,FiCO2=8%).Then tracheostomy was performed,and the experimental animals were ventilated for 3 hours after oleic acid or sterile normal saline administration.Lung mechanics,hemodynamics,blood-gas analysis were monitored.The rabbits were exsangninated.and the lungs and heart were taken out from the thorax.The concentration of superoxide dismutase(SOD)and malondialdehyde(MDA)in the lung tissue were assayed.Lung tissue wet/dry ratio and pulmonary permeability index were measured and histologic damage was assessed after three hours'mechanical ventilation.Results Peak airway pressure in Group H was significantly lower than that in Group N and the dynamic lung comphance Was significantly higher than that in Group N(P＜0.05).PaO2 in Group H was significantly higher than that in Group N(P＜0.05).The concentration of MDA in the lung tissue in group H was significantly lower than that in Group N(P＜0.05),and SOD in group H was significantly higher than that in Group N(P＜O.05).Lung tissue wet/dry ratio and pulmonary permeability in group H were significantly lower than that in Group N(P＜0.05).Histological tissus damage in Group N wassignificantly severer than that in Group H.Conclusions Hypercapnia induced by inhalation of high concentration of carbon dioxide(8%)plays protective role in this in vivo model of ALI.The mechanisms may be associated with enhanced SOD activity and the attenuation of lipid peroxidation in the lung tissue.