Empirical Study Of Intracavity ECG Characteristic P Wave Amplitude In PICC Catheter Tip Placement

Objective:To explore on the ratio of P-wave amplitude to QRS-wave amplitude in intracavity electrocardiogram at the best position of PICC catheter tip,in order to improve the accuracy of electrocardiogram（ECG）positioning technology in the diagnosis of catheter tip positioning,and to achieve the precise positioning of PICC catheter tip.Methods:The subjects were enrolled 180 patients underwent ultrasound-guided PICC catheterization in the Department of Hematology of a Third-Class Hospital from January to December2018.Aftersuccessfulcatheterization,Implementingintracavity electrocardiogram positioning.The gold standard chest radiograph determines the position of the catheter tip,which is divided into ideal position group,position too deep group and position too shallow group.According to the change of characteristic P wave amplitude in the literature and the pre-test results,the ratio of P wave amplitude to QRS wave amplitude is divided into five interval segments,which are≤30%interval segment,31%-40%interval segment,41%-50%interval segment,51%-60%interval segment,≥60%interval segment.The corresponding interval segments when the PICC catheter tip is located at the ideal position（T₆-T₇）,the too deep position（T₈-T₉）and the too shallow position（T₄-T₅）were discussed.The P/R ratio interval segment in which the catheter tip is located at the ideal position is obtained.Finally,the diagnostic test evaluation criteria were used to judge the effect of intracavitary ECG positioning technology.Results:A total of 180 patients were analyzed.1.The result of location.X-ray chest radiographs showed that 164（91.1%）patients had ideal catheter tip position,12（4.4%）were too deep,and 8（4.4%）were too shallow.Compared the basic data of ideal position group with that of deep position group or shallow position group,the difference was not statistically significant and comparable（P>0.05）.The results of the P/R ratio of intracavitary ECG localization showed that,there were 4 cases（2.2%）in the interval of≤30%,44 cases（24.4%）in the interval of 31-40%,86 cases（47.8%）in the interval of41%-50%,35 cases（19.4%）in the interval of 51-60%and 11 cases（6.1%）in the interval of≥60%.2.The location effect of P/R ratio.There was a statistically significant difference（P<0.001）between the positioning effect of each interval of P/R ratio.Further comparison between each two groups showed that:（1）The interval of P/R amplitud≤30%is significantly different from 31%-40%,41%-50%,51%-60%.Compared with the P/R ratio in the interval of≥60%,the difference is not statistically significant（P>0.05）.The ideal position rate of the catheter tip is 0 in the interval of the P/R ratio≤30%,90.1%in the interval of 31%-40%and 100%in the interval of 41%-50%or 51%-60%.The non-ideal position rate is 100%in the interval of the P/R ratio≤30%,9.1%in the interval of31%-40%,and 0 in the interval of 41%-50%or 51%-60%.（2）The different is not statistically significant between the P/R ratio in the interval of 31%-40%and the interval of41%-50%or 51%-60%（P>0.05）.However,there was significant difference when compared with that in the interval of≥60%（P<0.001）.The ideal location rate is 90.1%in31%-40%intervals and 27.3%in≥60%intervals.The non-ideal location rate is 9.1%in31%-40%intervals and 72.7%in≥60%intervals.（3）The difference between the P/R amplitude of 41%-50%or 51%-60%interval and the≥60%interval was statistically significant（P<0.001）.The ideal position rate was 100%in the range of 41%-50%or51%-60%and 27.3%in≥60%interval.The non-ideal position rate is 0 in the interval of41%-50%or 51%-60%,and 72.7%in the interval of≥60%.3.Diagnostic test results.The results of diagnostic tests showed that the accuracy of ECG positioning technique was97.77%and the sensitivity and specificity was 98.17%,and 93.75%respectively.The Yoden index was 0.92,the positive predictive value was 99.38%,and the negative predictive value was 83.33%.The ratio of Positive likelihood is 15.00,the ratio of negative likelihood is 0.02.The area under the ROC curve is 0.966 and the Kappa index is 0.867.Conclusion:The P/R amplitude ratio of ECG positioning technology has guiding significance for judging the position of catheter tip.The 41%-60%interval segment has the better positioning effect,while the≤30%and≥60%interval segment are not suitable for positioning.The sensitivity and specificity of electrocardiographic localization technique are high,and the area under ROC curve is nearly equal to 1.It is expected to become a new criterion for judging the tip position of PICC catheter and make up for the deficiency of X-ray.