Pulse Wave Velocity Measurement in the Carotid Artery Using an LED-LED Array Pulse Oximeter

Pulse wave velocity (PWV) is frequently used as an early indicator of risk of cardiovascular disease. Conventional methods of PWV measurement are invasive and measure the regional PWV, introducing errors from unknown measurement distance to masking local changes in compliance. This paper describes the development and testing of a non-invasive PWV sensor using photoplethysmograph signals. The sensor measures the pulse in the carotid artery with three sensor arrays spaced at 20 mm, 30 mm and 50 mm spacing. Each array of 20 LED-LED sensors are placed at 5 mm to get the largest amplitude pulse across the neck, and to allow for inaccurate sensor placement. LEDs are used as light emitters and the inherent capacitance of reverse biased LEDs measure the reflected light. The foot-foot and phase difference methods were used to calculate the PWV at each measurement distance. The foot-foot method was more reliable than the phase difference at all distances with a PWV of 5.26 ms(-1) in a single-subject trial. The sample rate of 570 Hz was deemed too slow as one sample difference resulted in a PWV change of 1.5 m s(-1). The developed sensor measured the local PWV within the expected physiological range around 6 m s(-1). All future measurements will be measured at 1 kHz and an increased LED output intensity. Copyright (C) 2020 The Authors.