IMR Press / FBE / Volume 15 / Issue 2 / DOI: 10.31083/j.fbe1502012
Open Access Original Research
Carotid Artery Corrected Flow Time Measured by Wearable Doppler Ultrasound Accurately Detects Changing Stroke Volume During the Passive Leg Raise in Ambulatory Volunteers
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1 Health Sciences North Research Institute, Sudbury, ON P3E 2H2, Canada
2 Flosonics Medical, Toronto, ON M5V 2Y1, Canada
3 Northern Ontario School of Medicine, Sudbury, ON P3E 2C6, Canada
*Correspondence: (Jon-Émile S. Kenny)
Front. Biosci. (Elite Ed) 2023, 15(2), 12;
Submitted: 3 September 2022 | Revised: 25 February 2023 | Accepted: 16 March 2023 | Published: 22 May 2023
(This article belongs to the Special Issue Frontiers in Biomedical Technology & Biomedicine)
Copyright: © 2023 The Author(s). Published by IMR Press.

This is an open access article under the CC BY 4.0 license.


Background: The change in the corrected flow time of the common carotid artery (ccFTΔ) has been used as a surrogate of changing stroke volume (SVΔ) in the critically-ill. Thus, this relatively easy-to-obtain Doppler measure may help clinicians better define the intended effect of intravenous fluids. Yet the temporal evolution of SVΔ and ccFTΔ has not been reported in volunteers undergoing a passive leg raise (PLR). Methods: We recruited clinically-euvolemic, non-fasted, adult, volunteers in a local physiology lab to perform 2 PLR maneuvers, each separated by a 5 minute ‘wash-out’. During each PLR, SV was measured by a non-invasive pulse contour analysis device. SV was temporally-synchronized with a wireless, wearable Doppler ultrasound worn over the common carotid artery that continuously measured ccFT. Results: 36 PLR maneuvers were obtained across 19 ambulatory volunteers. 8856 carotid Doppler cardiac cycles were analyzed. The ccFT increased nearly ubiquitously during the PLR and within 40–60 seconds of PLR onset; the rise in SV from the pulse contour device was more gradual. SVΔ by +5% and +10% were both detected by a +7% ccFTΔ with sensitivities, specificities and areas under the receiver operator curve of 59%, 95% and 0.77 (p < 0.001) and 66%, 76% and 0.73 (p < 0.001), respectively. Conclusions: The ccFTΔ during the PLR in ambulatory volunteers was rapid and sustained. Within the limits of precision for detecting a clinically-significant rise in SV by a non-invasive pulse contour analysis device, simultaneously-acquired ccFT from a wireless, wearable ultrasound system was accurate at detecting ‘preload responsiveness’.

carotid artery
corrected flow time
fluid responsiveness
passive leg raise
Fig. 1.
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