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. 2020 Jan 29;2(1):e0072.
doi: 10.1097/CCE.0000000000000072. eCollection 2020 Jan.

A Carotid Doppler Patch Accurately Tracks Stroke Volume Changes During a Preload-Modifying Maneuver in Healthy Volunteers

Jon-Émile S Kenny  1 , Igor Barjaktarevic  2 , Andrew M Eibl  1 , Matthew Parrotta  1 , Bradley F Long  1   3 , Joseph K Eibl  1   3 , Frederic Michard  4
Affiliations

A Carotid Doppler Patch Accurately Tracks Stroke Volume Changes During a Preload-Modifying Maneuver in Healthy Volunteers

Jon-Émile S Kenny et al. Crit Care Explor. .

Abstract

Objectives: Detecting instantaneous stroke volume change in response to altered cardiac preload is the physiologic foundation for determining preload responsiveness.

Design: Proof-of-concept physiology study.

Setting: Research simulation laboratory.

Subjects: Twelve healthy volunteers.

Interventions: A wireless continuous wave Doppler ultrasound patch was used to measure carotid velocity time integral and carotid corrected flow time during a squat maneuver. The Doppler patch measurements were compared with simultaneous stroke volume measurements obtained from a noninvasive cardiac output monitor.

Measurements and main results: From stand to squat, stroke volume increased by 24% while carotid velocity time integral and carotid corrected flow time increased by 32% and 9%, respectively. From squat to stand, stroke volume decreased by 13%, while carotid velocity time integral and carotid corrected flow time decreased by 24% and 10%, respectively. Both changes in carotid velocity time integral and corrected flow time were closely correlated with changes in stroke volume (r 2 = 0.81 and 0.62, respectively). The four-quadrant plot found a 100% concordance rate between changes in stroke volume and both changes in carotid velocity time integral and changes in corrected flow time. A change in carotid velocity time integral greater than 15% predicted a change in stroke volume greater than 10% with a sensitivity of 95% and a specificity of 92%. A change in carotid corrected flow time greater than 4% predicted a change in stroke volume greater than 10% with a sensitivity of 90% and a specificity of 92%.

Conclusions: In healthy volunteers, both carotid velocity time integral and carotid corrected flow time measured by a wireless Doppler patch were useful to track changes in stroke volume induced by a preload-modifying maneuver with high sensitivity and specificity.

Keywords: carotid ultrasound; corrected flow time; fluid responsiveness; stroke volume; velocity time interval.

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Conflict of interest statement

Drs. Kenny, Andrew M. Eibl, Parrotta, Long, and Joseph K. Eibl are working with Flosonics, a start-up developing a commercial version of the Doppler patch. Dr. Michard is the founder and managing director of MiCo, a Swiss consulting firm. MiCo does not sell any medical products, and Dr. Michard does not own shares nor receive royalties from any MedTech company. Dr. Barjaktarevic has disclosed that he does not have any potential conflicts of interest.

Figures

Figure 1.
Figure 1.
Overview of device. A, Novel hands-free Doppler patch placed over common carotid artery of a healthy volunteer and used to collect carotid velocity time integral and corrected flow time. B, To scale image of the Doppler patch. C, Spectrogram and metrics obtained from Doppler patch.
Figure 2.
Figure 2.
Illustration of stand-squat-stand preload-modifying maneuver. FTc = corrected flow time, SV = stroke volume, VTI = velocity time integral.
Figure 3.
Figure 3.
Results of preload-modifying maneuver. A, Individual percent changes in stroke volume, carotid velocity time integral (VTI), and carotid corrected flow time (FTc) during the squat maneuver (n = 22); (B) averaged absolute values for changes in stroke volume, VTI, and FTc during the squat maneuver (* p < 0.05, ** p < 0.01, *** p < 0.001).
Figure 4.
Figure 4.
Comparative statistics for stroke volume and carotid Doppler metrics. A and B, Four-quadrant plots comparing percent change in stroke volume on x-axis to percent change in carotid velocity time integral (VTI) and carotid corrected flow time (FTc) on y-axis, respectively. C and D, Optimal thresholds for changes in carotid VTI and changes in carotid FTc, respectively, to detect a change in stroke volume greater than 10% (delta stroke volume [SV]).
See this image and copyright information in PMC

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