The Influence Of Inhaling Different Concentration Oxygen On Children’s Lung Function In Anesthesia

BackgroundIn the process of pediatric anesthesia induction and maintenance, the use of pureoxygen has become a common phenonmenon in clinical anesthesia. Pure oxygen canprovide inceresed oxygen reserves and the hypoxia tolerance time of children. Thestudy about adults found that inhalation of high concentrations of oxgen for a longtime can cause lung damage, increase lung shunt fraction and affect the exchange oflung function. However these studys about children is very little. The currentmonitoring index of lung exchange include PA-aO2, PaO2/FiO2, PA-aO2/PaO2andPaO2/PAO2. These indicators can better reflect the lung exchange function, and thesecan also judge the existence of a switching barriers early. It has important significanceto prevent hypoxemia. This study obseved the impact of inhaled air on children’s lungfunction in anesthesia to provide the reference for clinical anesthesia use low oxygenconcentration.MethodApproved by the hospital ethics committee.40children scheduled for electivesurgery of lower extremity had been operated through general anaesthesia withtracheal intubation(all children with hip dislocation). Inclued25males and15females,ASAⅠ-Ⅱ,aged2years old-6yeaes old, wight10-20kilograms. They wererandomly assigned to two groups, which group had20children. Group A(low oxygenconcentration grpup) with FiO2=22%; Group B(pure oxgen group) with FiO2=100%.Anesthesia were induced by intravenous injection Atropine0.1-0.2mg/kg, Midazolam 0.1-0.2mg/kg, Sufentanil0.3ug/kg, Propofol2-3mg/kg, Cisatracurium1-2mg/kg.Maintain anesthesia using Dexmedetomidine0.6ug/kg/h and1-3%sevofluraneinhalation. According to the operation needs continuous intravenous injectionSufentanil0.2ug/kg. Use the bispectral index monitoring the sedative-hypnotic depthin the operation and keep the BIS value of two groups between40and60. Adjust theinhaled oxygen concentration makes FiO2=22%in group A(air group) andFiO2=100%in group B(pure oxygen group). All the children were mechanicallyventilated with VC model. Tidal volumes of6-8ml/kg body weight, I:E ratio on1:2,respiratory frequency was between15and22. According to the PetCO2adjust the VTand respiratory frequency, made the PetCO2in38-41mmHg and airway pressureunder23mmH2O. Record the hemodynamic parameters of two groups at thebeginning of the operation(T1) and affter the operation2hours(T2). Extracted theradial artery blood for blood gas analysis after the begin of the operation2hours andrecorded the results. According to the alveolar formula calculate the PAO2, PA-aO2,PA-aO2, PaO2/FiO2, PA-aO2/PaO2and PaO2/PAO2.Results1.Hemodynamic Index: Comparison between the two time poins in the group,the MAP and HR at T2time point was significantly lower than the T1, and thedifference was statistically significant(P＜0.05). Comparison between the groups, theMAP and HR at the same time points was no significant difference(P＞0.05).2.At the T2time point, PaO2of the group B was obviously higher than that ingroup A and the difference was statistically significant(P＜0.05); SpO2of the group Bslightly higher than that in group A and the difference was statistically significant (P＜0.05). There was no significant difference between the two groups on the PaCO23.Compared within the two groups, the PaO2/FiO2of the group B slightlyhigher than that in group A, but there was no significant difference(P＞0.05). ThePA-aO2of group B was obviously higher than that in group A and the difference wasstatistically significant(P＜0.05). PA-aO2/PaO2and PaO2/PAO2of group B comparedwith that of group A, the difference was statistically significant(P＜0.05) Conclusion:1.For children with normal lung function, suction air will not lead to hyoxemia inanesthesia maintain process. but also avoid the impact on lung exchange formintaking high concentration oxygen.2.For children with normal lung function, improving inhaled oxygenconcentration can increase the alveolar-arterial oxygen partial press difference(PA-aO2)， oxygen index(PaO2/FiO2) and respiratory index(RI=PA-aO2/PaO2), butreduce artery alveolar oxygen partial pressure ratio(PaO2/PAO2). Improving oxygenconcentration can affect the switching function.