Feasibility of cardiac output measurements in critically ill patients by medical students

Geert Koster, Thomas Kaufmann, Bart Hiemstra, Renske Wiersema, Madelon E Vos, Devon Dijkhuizen, Adrian Wong, Thomas W L Scheeren, Yoran M Hummel, Frederik Keus, Iwan C C van der Horst, Geert Koster, Thomas Kaufmann, Bart Hiemstra, Renske Wiersema, Madelon E Vos, Devon Dijkhuizen, Adrian Wong, Thomas W L Scheeren, Yoran M Hummel, Frederik Keus, Iwan C C van der Horst

Abstract

Background: Critical care ultrasonography (CCUS) is increasingly applied also in the intensive care unit (ICU) and performed by non-experts, including even medical students. There is limited data on the training efforts necessary for novices to attain images of sufficient quality. There is no data on medical students performing CCUS for the measurement of cardiac output (CO), a hemodynamic variable of importance for daily critical care.

Objective: The aim of this study was to explore the agreement of cardiac output measurements as well as the quality of images obtained by medical students in critically ill patients compared to the measurements obtained by experts in these images.

Methods: In a prospective observational cohort study, all acutely admitted adults with an expected ICU stay over 24 h were included. CCUS was performed by students within 24 h of admission. CCUS included the images required to measure the CO, i.e., the left ventricular outflow tract (LVOT) diameter and the velocity time integral (VTI) in the LVOT. Echocardiography experts were involved in the evaluation of the quality of images obtained and the quality of the CO measurements.

Results: There was an opportunity for a CCUS attempt in 1155 of the 1212 eligible patients (95%) and in 1075 of the 1212 patients (89%) CCUS examination was performed by medical students. In 871 out of 1075 patients (81%) medical students measured CO. Experts measured CO in 783 patients (73%). In 760 patients (71%) CO was measured by both which allowed for comparison; bias of CO was 0.0 L min-1 with limits of agreement of - 2.6 L min-1 to 2.7 L min-1. The percentage error was 50%, reflecting poor agreement of the CO measurement by students compared with the experts CO measurement.

Conclusions: Medical students seem capable of obtaining sufficient quality CCUS images for CO measurement in the majority of critically ill patients. Measurements of CO by medical students, however, had poor agreement with expert measurements. Experts remain indispensable for reliable CO measurements. Trial registration Clinicaltrials.gov; http://www.clinicaltrials.gov; registration number NCT02912624.

Keywords: Cardiac output; Critical care; Intensive care unit; Medical students; Ultrasonography.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Flow diagram of the Simple Intensive Care Studies-I (SICS-I). ICU intensive care unit, CCUS critical care ultrasonography, CO cardiac output, LVOT left ventricular outflow tract, VTI velocity time interval
Fig. 2
Fig. 2
Bland–Altman plot showing the comparison between cardiac output measured by medical students (COmedical student) and core lab experts (COexpert). The mean bias between COexpert and COmedical student and the upper and lower limits of agreement (LOA) are presented. The figure clearly shows the widening of the LOA in both directions with increasing CO

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