Accuracy of the BoMED NCCOM3 Bioimpedance Cardiac Output Monitor during Induced Hypotension: An Experimental Study in Dogs

Abstract

Changes in thoracic electrical bioimpedance during the cardiac cycle are utilised by the BoMed NCCOM3 monitor to measure cardiac output (COTEs)' The technique provides a continuous noninvasive measurement but it has not been widely accepted. To determine the accuracy of the monitor, we compared its measurement with cardiac output measured by dye dilution (CODnJ during induced hypotension and recovery in 23 dogs. After calibration of the NCCOM3 monitor during a resting state in each dog [mean blood pressure 112 ± 17 (SD), mean CODD 3.22 ± 0.99I1minj, the mean difference (COTEIrCODnJ between paired measurements at the nadir of hypotension (blood pressure 55 ± 24 mmHg) was 0.29 ± 0.47 IImin whose limits of agreement (mean difference ± 2 SD) were + 111.8% and-59.1% of the mean hypotensive CODD (l.1O ± 0.66I1min). Upon recovery from hypotension (mean blood pressue 102 ± 20 mmHg), the mean difference between paired measurements was-0.28 ± 0.66 IImin, whose limits of agreement were + 44.1% and-67.8% of the mean CO DD (2.36 ± 1.01 IImin). The mean difference between the two techniques is too variable and excessive to permit substitution of one technique for the other. These results do not support the accuracy and reliability of the BoMed NCCOM3 cardiac output monitor.

Evaluation of a minimally invasive non–calibrated pulse contour cardiac output monitor (FloTrac/Vigileo) in anaesthetized dogs

“…Additionally a Bland-Altman analysis of the ratio of _ Qt TD over _ Qt FloTrac was performed to correct for the increasing bias with increasing _ Qt values. To objectify the agreement of the method, the percentage bias (100% · mean bias/mean _ Qt of the two methods) and the percentage error (100% · (2 · SD of the bias)/mean _ Qt of the two methods) were calculated (Tibballs et al 1992;Critchley & Critchley 1999).…”

“…To objectify the agreement of the method, the percentage bias (100% × mean bias/mean Q̇t of the two methods) and the percentage error (100% × (2 × SD of the bias)/mean Q̇t of the two methods) were calculated (Tibballs et al. 1992; Critchley & Critchley 1999).…”

Comparison of cardiac output measurement using the CardioQPTM oesophageal Doppler with cardiac output measurement using thermodilution technique in children during heart catheterisation*

“…CardioQP underestimates CO values measured by TDT by about 20%, which can be explained by the absence of cerebral and upper limb blood flow in the descending aorta. However, the large mean percentage error of more than 30% caused by the large mean difference between paired CO values does not support the use of the CardioQP for the assessment of absolute CO values [7, 8].…”

“…The mean percentage error was calculated by two standard deviations divided by mean CO multiplied with 100. A mean percentage error not exceeding 30% was defined to indicate clinical useful reliability of the CardioQP [7, 8]. Data are presented as range and median, or mean and standard deviation, as appropriate.…”

Continuous noninvasive arterial pressure

“…This was estimated by the SD of repeated measurements of AP from 60 consecutive pulse beats in each patient, also called the within-subject SD [13][14][15] for IAP and CNAP, respectively. The size of percentage measurement error was calculated by twice the within-subject SD divided by the population mean AP [16]. Given no significant difference between the sizes of the measurement errors, one would accept the hypothesis that IAP and CNAP are interchangeable [15].…”