title: Reliability of thermodilution derived cardiac output with different operator characteristics.
abstract: Cardiac output (CO) is commonly measured using the thermodilution technique at the time of right heart catheterisation (RHC). However inter-operator variability, and the operator characteristics which may influence that, has not been quantified. Therefore, this study aimed to assess inter-operator variability with the thermodilution technique using a mock circulation loop (MCL) with calibrated flow sensors. Participants were blinded and asked to determine 4 levels of CO using the thermodilution technique, which was compared with the MCL calibrated flow sensors. The MCL was used to randomly generate CO between 3.0 and 7.0 L/min through changes in heart rate, contractility and vascular resistance with a RHC inserted through the MCL pulmonary artery. Participant characteristics including gender, specialty, age, height, weight, body-mass index, grip strength and RHC experience were recorded and compared to determine their relationship with CO measurement accuracy. In total, there were 15 participants, made up of consultant cardiologists (6), advanced trainees in cardiology (5) and intensive care consultants (4). The majority (9) had performed 26-100 previous RHCs, while 4 had performed more than 100 RHCs. Compared to the MCL-measured CO, participants overestimated CO using the thermodilution technique with a mean difference of +0.75 ± 0.71 L/min. The overall r2value for actual vs measured CO was 0.85. The difference between MCL and thermodilution derived CO declined significantly with increasing RHC experience (P < 0.001), increasing body mass index (P < 0.001) and decreasing grip strength (P = 0.033). This study demonstrated that the thermodilution technique is a reasonable method to determine CO, and that operator experience was the only participant characteristic related to CO measurement accuracy. Our results suggest that adequate exposure to, and training in, the thermodilution technique is required for clinicians who perform RHC.
authors.affiliation: Faculty of Health Sciences, School of Medicine, The University of Queensland, Brisbane, QLD, Australia.|The Prince Charles Hospital, Chermside, QLD, Australia.
authors.forename: Scott C
authors.initials: SC
authors.lastname: McKenzie
authors.affiliation: Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.
authors.forename: Kimble
authors.initials: K
authors.lastname: Dunster
authors.affiliation: Faculty of Health Sciences, School of Medicine, The University of Queensland, Brisbane, QLD, Australia.|The Prince Charles Hospital, Chermside, QLD, Australia.
authors.forename: Wandy
authors.initials: W
authors.lastname: Chan
authors.affiliation: Faculty of Health Sciences, School of Medicine, The University of Queensland, Brisbane, QLD, Australia.|The Prince Charles Hospital, Chermside, QLD, Australia.
authors.forename: Martin R
authors.initials: MR
authors.lastname: Brown
authors.affiliation: Faculty of Health Sciences, School of Medicine, The University of Queensland, Brisbane, QLD, Australia.|The Prince Charles Hospital, Chermside, QLD, Australia.|Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.
authors.forename: David G
authors.initials: DG
authors.lastname: Platts
authors.affiliation: The Prince Charles Hospital, Chermside, QLD, Australia.
authors.forename: George
authors.initials: G
authors.lastname: Javorsky
authors.affiliation: Faculty of Health Sciences, School of Medicine, The University of Queensland, Brisbane, QLD, Australia.|Nambour General Hospital, Nambour, QLD, Australia.
authors.forename: Chris
authors.initials: C
authors.lastname: Anstey
authors.affiliation: Faculty of Health Sciences, School of Medicine, The University of Queensland, Brisbane, QLD, Australia. shaun.gregory1@gmail.com.|Innovative Cardiovascular Engineering and Technology Laboratory, Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia. shaun.gregory1@gmail.com.|School of Engineering, Griffith University, Brisbane, Australia. shaun.gregory1@gmail.com.
authors.forename: Shaun D
authors.initials: SD
authors.lastname: Gregory
mesh_terms: D000328:Adult; D002138:Calibration; D006328:Cardiac Catheterization / Q000379:methods*; D002302:Cardiac Output; D002407:Catheterization, Swan-Ganz; D005260:Female; D018737:Hand Strength; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D015588:Observer Variation; D011651:Pulmonary Artery / Q000473:pathology; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013815:Thermodilution / Q000379:methods*
keywords: Cardiac output; Clinical measurements; Measurement precision; Pulmonary artery catheterisation; Thermodilution