Experimental Study Of High Frequency Oscillatory Ventilation Combined With Incremental Positive End-expiratory Pressure For The Treatment Of Smoke Inhalation Injury

Objective：To observe the effects of high frequency oscillatory ventilation combined withincremental positive end-expiratory pressure on respiration,circulation function andinflammatory response together with lung histologyin in dogs with smoke inhalationinjury,and to preliminarily reaserch the possible mechanism.Method：Twenty-four healthy local male dogs anesthetized intubated, and ventilated byBabylog8000plu（sDr ger）ventilator conventional mechanical for30min.After severesmoke inhalation injury dogs model was made,HFOV completely controlledbreathing for another30min.Dogs were divided into three groups:conventionalmandatory ventilation group(control group, n=8)，pure HFOV group (HFOV group,n=8) and HFOV combined with incremental PEEP group(HFOV+IP group, n=8)according to the random number table.Then conventional mandatory ventilation,purehigh frequency oscillatory ventilation and high frequency oscillatory ventilationcombined with incremental positive end-expiratory pressure were continuedrespectively.Animal performance,as well as pneodynamics、 hemodynamicsparameters and blood gas analysis results before injury, after induced, and aftertreatment of2h,4h,6h,8h were observed and recorded,the contents of TNF-α, IL-10inserum were detected at each time point by the enzyme-linked immunosorbent assay(ELISA).Animals were killed after8h ventilation,different parts of the lung tissueswere obtained for injury score and histological observation,and inflammatory factorTNF-α, IL-10in the right lower lung homogenates were detected by ELISA method.Results：（1）Pneumodynamics：PIP had significantly decreased in three groups of dogs afterventilation,both HFOV and HFOV+IP groups were significantly lower than controlgroup while ventilation(P<0.05or P<0.01),which was the lowest in the HFOV+IPgroup（P<0.05）;Compared with the control group,Pmean showed no significantlychange in HFOV and HFOV+IP groups after ventilation.Dynamic compliance(Cdyn) had elevated after injured,and both HFOV and HFOV+IP groups were significantlyhigher than the control group at each timepoint;while compared with the HFOVgroup,Cdyn level was obviously higher in HFOV+IP groupat at4h、6h、8hpoints(P<0.05or P<0.01).Airway resistance(Raw) showed no significant change ateach time point (P>0.05).Compared with the control and HFOV group, there stillshowed no significantly change in the HFOV+IP group(P>0.05).（2）Hemodynamics：at each timepoints of the three groups of dogs before andafter injury,heart rate (HR), mean arterial pressure (MAP), pulmonary artery pressure(PAP) and central venous pressure (CVP) and other hemodynamic parameters hadshowed no significant difference(P>0.05).In HFOV+IP group,cardiac output (CO)was lower than pre-injury at the pionts of4h,6h and8h ventilation,which also showedstatistical significance at each time point between groups(P <0.05or P <0.01).（3）Arterial blood gas analysis：After inhalation injury established PaO2in thethree groups significantly decreased (P<0.01),which increased since2h aftertreatment and sustained at favorite levels during4h treatment period (P<0.05);Compared with the control group,PaO2in both HFOV and HFOV+IP groups wereobviously higher (P<0.05); PaO2was higher at4h、6h and8h points in HFOV+IPgroup while compared with the HFOV group(P<0.01).The pH and PaCO2had nosignificant difference in the three groups at different treatment timepoints (P>0.05).（4）Inflammatory response:the levels of TNF-α had significantly decreased andthe content of IL-10had raised in both HFOV and HFOV+IP group while comparedwith the control group(P<0.05).When compared with the HFOV group,the levels ofTNF-α had significantly decreased and the content of IL-10had raised in HFOV+IPgroup at6h、8htimepionts(P<0.05).The contents of TNF-α in lung homogenate weresignificantly lower in both HFOV and HFOV+IP groups than control group,whichwas the lowest in HFOV+IP group (P<0.05);and the contents of IL-10in lunghomogenate were significantly higher in both HFOV and HFOV+IP groups thancontrol group,which was the highest in HFOV+IP group(P<0.05).(5)Pathological examination and histological injury found that the lung injurydegree were more alliviated both in HFOV and HFOV+IP group than which in thecontrol group,and the lowest in HFOV+IP group(P<0.05).The lung injury scores were respectively（4.38±0.19），（3.38±0.21），（2.97±0.23）in the three groups.Conclusions：1、HFOV combined with incremental PEEP(IP) can effectively improve thepulmonary gas exchange and lung compliance,but with adverse effect to CO.2、 HFOV combined with incremental PEEP could significantly improveinflammatory response and the lung injury, which maybe an ideal model ofventilation for the treatment of smoke inhalation injury.