A comparison of thoracic bioimpedance and pulse contour analysis in cardiac output monitoring in critically ill

Abstract

Hemodynamic monitoring is an important tool especially in critical care unit. The monitoring is varied from invasive cardiac output monitoring to noninvasive cardiac output monitoring. The trends are shifted to non-invasive cardiac output monitoring because it has good correlations with gold standard cardiac output monitoring. Latest invention of thoracic bioimpedance using signal morphology impedance cardiology is new to measure of cardiac output especially in critical care. However, there is limited number of studies comparing this device and gold standard monitoring. Total of 23 patients admitted to intensive care unit, SASMEC that required PiCCO monitoring enrolled in this study. All patients were in septic shock with SOFA score of > 4. Cardiac output parameters were taken using both machines concurrently, at 1,6,12, and 24 hours. Parameters taken were cardiac output, cardiac index, stroke volume, stroke volume index, systemic vascular resistance, and systemic vascular resistance index. Correlation analysis was done by using Pearson’s correlation, and mean difference was tested using paired t test and correlation between these two methods were tested using Bland Altman test. Pearson’s r correlation coefficient where the result showed significant correlation for 4 different stages of reading for systemic vascular resistance with R of R: 0.92 at first hour, 0.543 at 6 hour, 0.638 at 12 hour, and 0.551 at 24 hour ( P value of < 0.05). The first hour reading of systemic vascular reason showed strong correlation, with R 0.92 while the other next 3 readings were moderate in correlation. Other than that, there was moderate correlation of stroke volume r: 0.426 with P value < 0.005. Moderation correlation seen in stroke volume index at stage 2 (R 0.383), stage 3 (R 0.504) and stage 4 (R 0.411) together with stroke volume also showed moderate correlation at stage 3 (R 0.426) and stage 4 (R 0.411). There were significant differences at stage 3 and 4 (p- value <0.05) in stroke volume index while Cardiac index only showed significant in difference in stage 4. Bland Altman showed discrepancy result between both tools and presence of bias. In conclusion, all cardiac output parameters were statistically not significant except systemic vascular resistance. Reading hemodynamic parameters from Physioflow were not interchangeable with transpulmonary thermodilution.