Reproducibility of estimated cardiovascular function by transthoracic bioimpedance cardiography in healthy volunteers.
In ten healthy volunteers, stroke index (SI), heart rate (HR), thoracic fluid conductivity (TFC) and index of contractility (IC) were estimated by transthoracic bioimpedance measurements (BoMed Noninvasive Continuous Cardiac Output Monitor, model 3, Revision 7 (NCCOM3-R7)). Intra- and inter-observer variability and the influence of time of day (morning or afternoon) were determined. The intra-observer variability was significantly smaller during the morning than during the afternoon. The mean differences +/- standard error between consecutive measurements for morning versus afternoon measurements were, respectively: SI, 0.8 +/- 1.2 vs. 4.6 +/- 1.2 ml/m2 (P = 0.057); HR, -1.0 +/- 0.6 versus -0.9 +/- 0.6 beats/min; TFC, -0.0 +/- 0.3 vs. 1.0 +/- 0.3 (= TFC x 1000.omega-1) (P = 0.031) and IC, -0.6 +/- 0.9 vs. 5.6 +/- 0.9 (= IC x 1000.s-1) (P = 0.001). The inter-observer variability for SI, HR, TFC and IC did not reach statistical significance. These data suggest that reproducible measurements can be obtained provided that only morning or afternoon measurements are compared. Since the reproducibility of measurements was better during the morning than during the afternoon, we recommend that measurements are performed in the morning.
van Oppen
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Department of Obstetrics and Gynaecology, Utrecht University Hospital, The Netherlands.
van der Tweel
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Bruinse
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HW
D000328:Adult; D002307:Cardiography, Impedance / Q000295:instrumentation; D004553:Electric Conductivity; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D009200:Myocardial Contraction / Q000502:physiology; D015588:Observer Variation; D015203:Reproducibility of Results; D013318:Stroke Volume / Q000502:physiology; D013909:Thorax / Q000502:physiology; D013997:Time Factors