呼气末正压对超声测量下腔静脉直径及变异度的影响

Effects of different positive end-expiratory pressures on internal caliber of inferior vena cava and variation of cardiac output after volume expansion measured by transthoracic echocardiography in patients under mechanically respiratory support

目的应用床旁超声测量机械通气患者下腔静脉（IVc）内径及其呼吸变异度来评估其容量反应性，并观察呼气末正压（PEEP）对上述指标的影响。方法前瞻性选取2013年2月至2014年12月入住安徽医科大学第二附属医院重症医学科行机械通气患者40例。PEEP=0时超声测量IVc最大径（IVcDmax）、最小径（IVcDmin），计算IVc扩张指数（dIVc）。依据补液试验后心输出量增加是否≥15％将患者分为容量反应（＋）组和（-）组。R0c曲线分析IVcDmax、dIVc预测容量反应性的价值；将PEEP依次设置为5、10、15cmH20（1cmH20=0．098kPa）后，再次测量并分析IVCDmax、dIVC与PEEP的相关性及变化趋势。结果容量反应（＋）22例，（-）18例。IVcDmax和dIVc预测容量反应性的ROc曲线下面积分别为O．85（95％CI0．79—0．91）和0．95（95％c，0．91～O．98），均P〈O．001；以液体负荷前IVcDmax2．03cm为阈值预测容量反应性的敏感度、特异度分别为68．1％、94．3％；以dIVc12．40％为阈值预测容量反应性的敏感度、特异度分别为80．7％、98．6％。随PEEP递增，容量负荷试验（＋）组的dIVc组间存在总体差异性（P〈0．05），IVCDmax线性趋势检验P值〈0．01。PEEP与IVCDmax（r=0．35，P=0．001）、dIVc（r=-0．59，P=0．000）变化存在相关性。容量负荷试验（-）组IVcDmax线性趋势检验P值〈0．05，dIVc组问比较及其线性趋势检验均P值〉0．05。PEEP与IVcDmax变化存在相关性（r=0．28，P=0．019）；与dIVc变化无相关性（r=-0．04，P=0．771）。结论超声测量IVcDmax及dIVc可用于评价患者容量反应性，dIVc预测价值更高。PEEP可对该两项指标测量产生影响，尤其对容量反应阳性者。

Objective To evaluate the variation of internal caliber of inferior vena cava （IVC） during volume expansion measured by transthoracic eehocardiography in patients under mechanically respiratory support with different positive end-expiratory pressure （PEEP）. Methods Forty mechanical ventilated patients admitted to ICU from February 2013 to December 2014 were enrolled for prospective study. The maximum diameter of IVC （ IVCDmax ） and minimum diameter of IVC （ IVCDmin ） during PEEP = 0 were measured by using transthoracie echocardiography, and the dilatation index of IVC （ dlVC ） was calculated. The patients were divided into positive fluid responsiveness group and negative fluid responsiveness group according to the cardiac output （CO） increased over 15% or not after fluid therapy. ROC curve was employed to analyze dlVC and IVCDmax to predict the value of responsiveness. The relevance and variation trend among IVCD dlVC and PEEP were measured and analyzed after setting up the PEEP levels to 5, 10, 15 cm H2 0 successively. Results Of 40 patients, there were 22 assigned into positive group and 18 into negative group. The areas under ROC curve of volume responsiveness predicted by IVCDmax and dlVC were 0. 85 （95% C10. 79-0. 91 ） and 0. 95 （95% CI0. 91-0. 98 ） , respectively （ both P 〈 0. 01 ）. The sensitivity and specificity of predicted responsiveness by transthoracic echocardiography were 68.1% and 94. 3% , respectively, when 2. 03 cm was the optimal cut-off point of IVCDmax before fluid therapy. The sensitivity and specificity were 80. 7% and 98.6%, respectively, when 12. 40% was the optimal cut-off point of dlVC. In the fluid responsiveness positive group, as PEEP increased, there were differences in dlVC between groups （P 〈 0. 05 ）, and the P value of linear trend test of IVCDmax was 〈 0. 01. There were correlations between PEEP and IVCD （r =0. 35, P =0. 001 ）, dlVC （r = -0. 59, P = 0. 000）. In the fluid responsiveness negative group, as PEEP increased, the P value of linear trend test of IVCDmax was 〈 0. 05. The P values of inter-groups and linear trend test of dlVC were 〉 0. 05. There was correlation between PEEP and IVCDmax （r =0. 28, P =0. 019） , no correlation between PEEP and dlVC （r = -0. 04, P = 0. 771 ）. Conclusion Both IVCDmax, and dlVC measured by transthoracic echocardiography could be employed to evaluate responsiveness of patients, and the value of dlVC was higher. PEEP could influence the measurement of the two parameters, especially in fluid responsiveness positive patients.