Year : 2014 | Volume
: 17 | Issue : 4 | Page : 278-
Comparison between continuous noninvasive estimated cardiac output by pulse wave transit time and thermodilution method
Department of Critical Care and Anesthesiology, Medanta Institute of Critical Care and Anesthesiology, Medanta The Medicity, Sector 38, Gurgaon, Haryana, India
|How to cite this article:|
Mehta Y. Comparison between continuous noninvasive estimated cardiac output by pulse wave transit time and thermodilution method.Ann Card Anaesth 2014;17:278-278
|How to cite this URL:|
Mehta Y. Comparison between continuous noninvasive estimated cardiac output by pulse wave transit time and thermodilution method. Ann Card Anaesth [serial online] 2014 [cited 2020 Jul 4 ];17:278-278
Available from: http://www.annals.in/text.asp?2014/17/4/278/142060
An ideal cardiac output (CO) monitor should be minimally or noninvasive, continuous, cost effective, reproducible particularly during various physiological states and have a fast response time.  Methods of CO monitoring are broadly classified as:  Invasive, minimally invasive and noninvasive.
Pulmonary artery catheter (PAC) thermodilution is still considered the "gold standard" for CO estimation since its invention by Swan et al.  Gore et al.  and SUPPORT trial  showed that PAC use increased mortality after myocardial infarction, therefore, newer non or less invasive devices are being developed and validated in different clinical scenarios.
In this issue Sinha et al.  have tried to validate/correlate pulse wave transit time (PWTT) technique with eeCCO (estimated continuous cardiac output life sciences monitoring system which estimates the PWTT from the time gap between electrocardiogram (ECG)-R wave and the peripheral pulse detected by pulse oximeter in a mixed population of patients of coronary artery bypass graft, aortic valve replacement (AVR), aortic reconstruction and liver transplant. Liver transplant patients have a low systemic vascular resistance and may have a high output state.  This would affect the PWWT as would it happen in AVR due to high pulse pressure.
In this study, the esCCO estimated higher or lower values of CO by error almost equal to - of the actual CO. Seventy percent over/under estimation of CO can significantly alter the course of therapy, e.g. inotropes, vasodilators or volume and subsequently affect the clinical outcome with disastrous results.
The main advantage of PWTT technique is the noninvasiveness. You only need ECG and SpO 2 /noninvasive blood pressure to get the stroke volume and CO but the correlation between PAC and this has to be good enough with minimal bias, good precision and limits of agreement to be clinically reliable.
It is a well-planned and conducted paper with negative results. Authors have discussed the statistical method in detail with unbiased conclusions explaining the pitfalls of statistics, e.g. low bias in their paper! Till further work shows it. Otherwise, the jury is still out on PWTT technology for CO estimation.
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