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. 2021;29(5):859-868.
doi: 10.3233/THC-202626.

Measurement of pulse transit time using ultra-wideband radar

Hui-Sup Cho, Young-Jin Park

Measurement of pulse transit time using ultra-wideband radar

Hui-Sup Cho et al. Technol Health Care. 2021.

Abstract

Background: The pulse transit time is an important factor that can be used to estimate the blood pressure indirectly. In many studies, pressures in the artery near and far from the heart are measured or the electrocardiogram and photoplethysmography are used to calculate the pulse transit time. In other words, the so-called contact measurements have been mainly used in these studies.

Objective: In this paper, a new method based on radar technology to measure the pulse transit time in a non-contact manner is proposed.

Methods: Radar pulses were simultaneously emitted to the chest and the wrist, and the reflected pulses were accumulated. Heartbeats were extracted by performing principal component analysis on each time series belonging to the accumulated pulses. Then, the matched heartbeat pairs were found among the heartbeats obtained from the chest and wrist and the time delay between them, i.e. the pulse transit time, was obtained.

Results: By comparing the pulse transit times obtained by the proposed method with those obtained by conventional methods, it is confirmed that the proposed method using the radar can be used to obtain the pulse transit time in a non-contact manner.

Keywords: Ultra-wide band; heartbeat; impulse radar; principal component analysis; pulse transit time.

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Conflict of interest statement

The authors declare no conflict of interests.

Figures

Figure 1.
Figure 1.
Experimental setup for measuring heartbeats from the chest and the wrist.
Figure 2.
Figure 2.
Shapes of (a) frame and (b) frame set (area marked in red indicates IOI).
Figure 3.
Figure 3.
(a) The frame set obtained from the chest, (b) the shape after it passes through band-pass filter – top view, (c) the frame set obtained from the wrist, and (d) the shape after it passes through band-pass filter – top view (the red squares represent the IOI).
Figure 4.
Figure 4.
Shapes of the restored signals from (a) the chest IOI and (b) the wrist IOI with black line and their heartbeat locations with blue stems.
Figure 5.
Figure 5.
Process of aligning the heartbeat train for PTT calculation.
Figure 6.
Figure 6.
Waveforms of ECG, PPG, and heartbeat waveform of the chest and the wrist that are obtained by the proposed method.
Figure 7.
Figure 7.
Shapes of aligned heartbeat trains (upper plane indicates the R peaks and the characteristic points of the PPG, and lower plane indicates the heartbeat train pair obtained from the chest and wrist).
See this image and copyright information in PMC

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