Effect Of Mechanical Ventilation With Cold Air On Body Temperature And Respiratory In Dogs

Objective: To investigate the effect of mechanical ventilation with cold air on body temperature, pneodynamics , blood gas parameters and histological changes of lung tissues in dogs.To search for a new method to lower body temperature and its effect on respiratory.Methods:Eighteen healthy male dogs were randomly divided into two groups, hypothermia group(n=9) and normothermia group(n=9).The animals were ventilated with cold air(4℃) and normal air(25℃) respectively,ventilation parameters were set as (VT=15ml/kg,RR=15bpm,I:E=1:2) in each group. The body temperatures(Tnp, Tb,Ta) were recorded immediately and repeatedly every 30mins until 240min post-intubation. Blood gas parameters(PaO2,PaCO2,PH) and pneodynamic parameters (Raw,Ppeak,Cstat)were measured at 0min,30min,1hour,2hours,3hours and 4hours after intubation. Plasma cytokine(TNF-αlpha,IL-6)concentrations at 0min, 2hours and 4hours were determined by ELISA,And histopathologic appearance of lung tissue was analyzed by light microscopy.Results: There were no significant differences in all values of body temperatures between the two groups(P>0.05); PaO2 in the hypothermia group at 30min was significantly lower than normothermia group(367.02±17.10[hypothermia]vs388.69±10.99[normothermia]mmHg)(P<0.01),There were no differences in PaO2 except that of 30min between the hypothermia group and the normothermia group (P>0.05); There were no statistical significances in PaCO2 , PH, Raw,Ppeak,Cstat values at different time between the hypothermia group and the normothermia group.In addition, Plasma IL-6 concentrations at 2h and 4h increased significantly in both groups compared with basal level. However, serum IL-6 at 2h and 4h significantly lower in hypothermia compared with normothermia group(at 2hours; 0.29±0.02 [hypothermia] vs 0.31±0.33[normothermia]ng·mL-1;at 4hours 0.28±0.02 [hypothermia] ng·mL-1vs0.30±0.03[normothermia] ng·mL-1);Plasma TNF-αconcentrations at 2h points significantly increased in both groups compared with basal level.But there were no significant differences in Plasma TNF-αconcentrations between the two group.and Cumulative mean histology scores showed a lower score in hypothermia group(2.44±1.03) compared with normothermia group(4.01±1.31) (P<0.05).Conclusion: These results indicate that cold air ventilation has no effect on body temperature.And cold air ventilation has no influences on pneodynamics and gas exchange.Furthermore ,cold air(4℃) ventilation has beneficial effect on attenuated the elevation of serum IL-6 concentrations and attenuate injury in lung tissues compared with normal air mechanical ventilation.