Abstract
Pulse wave analysis enables stroke volume to be estimated from an arterial blood pressure waveform. Multi-beat analysis is a novel pulse wave analysis method. We aimed to investigate cardiac output (CO) estimations using multi-beat analysis of the radial arterial blood pressure waveform in patients undergoing off-pump coronary artery bypass surgery (OPCAB) using intermittent pulmonary artery thermodilution (PATD) as the reference method. This was a prospective clinical method comparison study. In 58 patients, we measured CO using PATD (PATD-CO; reference method) and simultaneously recorded the radial arterial blood pressure waveform that we used for off-line estimation of CO based on multi-beat analysis (MBA-CO; test method) using the Argos CO monitor (Retia Medical; Valhalla, NY, USA). The final analysis was performed using 572 paired CO measurements. We performed Bland–Altman analysis accounting for multiple observations per patient. To describe the ability of the test method to track changes in CO over time we computed four-quadrant plots using a central exclusion zone of 15% and calculated the concordance rate. Mean PATD-CO was 4.13 ± 1.26 L/min and mean MBA-CO was 4.31 ± 1.25 L/min. The mean of the differences between PATD-CO and MBA-CO was − 0.20 L/min with a standard deviation of ± 1.14 L/min and 95% limits of agreement of − 2.48 to + 2.08 L/min. The concordance rate for CO changes between PATD-CO and MBA-CO was 89%. CO estimations using multi-beat analysis (Argos monitor) show reasonable agreement and trending ability compared with PATD-CO as the reference method in adult patients during OPCAB.
Highlights
Cardiac output (CO) monitoring is recommended in highrisk surgical and critically ill patients [1,2,3]
We performed intermittent pulmonary artery thermodilution (PATD) measurements to assess reference CO values and simultaneously recorded the radial arterial blood pressure waveform that we used for off-line estimation of CO by multi-beat analysis (MBA) using the Argos CO monitor
To assess the agreement between PATD-CO and MBACO we performed Bland–Altman analysis accounting for multiple observations per patient [14] and calculated the mean and standard deviation (SD) of the differences, and the 95% limits of agreement (= mean difference ± 1.96 × SD of the difference), and the percentage error [15]
Summary
Cardiac output (CO) monitoring is recommended in highrisk surgical and critically ill patients [1,2,3]. Various methods for CO estimation with different physical measurement principles and degrees of invasiveness are available [4, 5]. Uncalibrated pulse wave analysis, the estimation of stroke volume based on the analysis of the arterial blood pressure waveform, constitutes a minimally invasive method and enables CO to be estimated continuously [3, 6,7,8]. One method to mathematically analyze the radial arterial blood pressure waveform to estimate stroke volume and CO is the so-called multi-beat analysis (MBA) [9, 10]. This method assumes a Windkessel model of the cardiovascular system.
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