Fig. 1

The wireless, wearable Doppler biosensor. A The device on a healthy volunteer. B The carotid artery Doppler spectrogram with the area under the velocity time curve, or velocity time integral (VTI), and flow time (FT) demarcated by the onset and end of systole. The FT is corrected for heart rate by the equation of Wodey to give the carotid corrected flow time (ccFT). The VTI for a single cardiac cycle represents the distance traveled by the blood, in centimeters, per beat. The ccFT is the duration of mechanical systole in milliseconds, corrected for heart rate by the equation of Wodey [22]