A wearable carotid Doppler tracks changes in the descending aorta and stroke volume induced by end‐inspiratory and end‐expiratory occlusion: A pilot study

Figures

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  Figure 1. The wireless Doppler ultrasound patch. A, Wireless, hands‐free Doppler patch placed over common carotid artery of a healthy volunteer. B, Scaled image of the Doppler patch. C, Metrics obtained from wearable Doppler

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  Figure 2. Relationships between carotid VTI, aortic VTI, and SV. A, Relationship between aortic VTI as gold standard and change in carotid VTI. The asterisk notes the single point of discordance on the four‐quadrant plot. B, Relationship between SV as gold standard and change in aortic VTI. C, Relationship between SV as gold standard and change in carotid VTI. The y‐axis is percent change for all panels. See text for details. SV, stroke volume; VTI, velocity time integral

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  Figure 3. Summary data from simulated occlusion tests. A, Percent change on the y‐axis for all subjects for all Doppler metrics, across T1, T2, and T3 on the x‐axis; bars represent SE. B, Coefficient of variation on the y‐axis for all subjects for all Doppler metrics across T1, T2, and T3 on the x‐axis. C, Data from an individual with a slow aortic response across the entire maneuver; each dot from the carotid and aorta represent one heartbeat, while the SV represents 20 second data points from the pulse contour analysis device. D, An individual with carotid “overshoot” early in the sEEOT. The y‐axis is percent change and the same for both subjects; T1, T2, and T3 are highlighted for clarity. sEEOT, simulated end‐expiratory occlusion test; sEIOT, simulated end‐inspiratory occlusion test; SV, stroke volume; VTI, velocity time integral