Cardiac Output Monitoring by Pulse Contour Analysis, the Technical Basics of Less-Invasive Techniques.

Jörn Grensemann

doi:10.3389/fmed.2018.00064

Abstract

Routine use of cardiac output (CO) monitoring became available with the introduction of the pulmonary artery catheter into clinical practice. Since then, several systems have been developed that allow for a less-invasive CO monitoring. The so-called “non-calibrated pulse contour systems” (PCS) estimate CO based on pulse contour analysis of the arterial waveform, as determined by means of an arterial catheter without additional calibration. The transformation of the arterial waveform signal as a pressure measurement to a CO as a volume per time parameter requires a concise knowledge of the dynamic characteristics of the arterial vasculature. These characteristics cannot be measured non-invasively and must be estimated. Of the four commercially available systems, three use internal databases or nomograms based on patients’ demographic parameters and one uses a complex calculation to derive the necessary parameters from small oscillations of the arterial waveform that change with altered arterial dynamic characteristics. The operator must ensure that the arterial waveform is neither over- nor under-dampened. A fast-flush test of the catheter–transducer system allows for the evaluation of the dynamic response characteristics of the system and its dampening characteristics. Limitations to PCS must be acknowledged, i.e., in intra-aortic balloon-pump therapy or in states of low- or high-systemic vascular resistance where the accuracy is limited. Nevertheless, it has been shown that a perioperative algorithm-based use of PCS may reduce complications. When considering the method of operation and the limitations, the PCS are a helpful component in the armamentarium of the critical care physician.

Highlights

Ill patients often receive extended hemodynamic monitoring with measurement or estimation of cardiac output (CO) as an aid for guiding fluid and vasopressor therapy
The aim of this review is to focus on the technical basics of uncalibrated pulse contour methods for monitoring of CO
Since the CO is only estimated according to different algorithms, the pulse contour analysis methods are error prone when used in critically ill patients who often have a low systemic vascular resistance (SVR), i.e., in septic shock as outlined earlier

Summary

INTRODUCTION

Ill patients often receive extended hemodynamic monitoring with measurement or estimation of cardiac output (CO) as an aid for guiding fluid and vasopressor therapy. Transpulmonary thermodilution techniques have been introduced, still allowing for a measurement of CO while less invasive, only requiring a central venous and an arterial line that are often used for standard hemodynamic monitoring in intensive care patients [4]. The less- or minimal-invasive methods estimate a CO from an arterial pulse contour waveform [5,6,7] and require only a conventional arterial line to obtain an input signal. Since arterial impedance and arterial compliance cannot be measured non-invasively, all PCS must obtain a good estimate of these parameters. This system samples the arterial waveform at 100 Hz and determines CO in 20 s intervals by a multiplication of the pulse rate with the SD of the arterial pressure

Method

LIMITATIONS

Findings

CONCLUSION