Weighing Scale-Based Pulse Transit Time is a Superior Marker of Blood Pressure than Conventional Pulse Arrival Time

Abstract

Pulse transit time (PTT) is being widely pursued for cuff-less blood pressure (BP) monitoring. Most efforts have employed the time delay between ECG and finger photoplethysmography (PPG) waveforms as a convenient surrogate of PTT. However, these conventional pulse arrival time (PAT) measurements include the pre-ejection period (PEP) and the time delay through small, muscular arteries and may thus be an unreliable marker of BP. We assessed a bathroom weighing scale-like system for convenient measurement of ballistocardiography and foot PPG waveforms – and thus PTT through larger, more elastic arteries – in terms of its ability to improve tracking of BP in individual subjects. We measured “scale PTT”, conventional PAT, and cuff BP in humans during interventions that increased BP but changed PEP and smooth muscle contraction differently. Scale PTT tracked the diastolic BP changes well, with correlation coefficient of −0.80 ± 0.02 (mean ± SE) and root-mean-squared-error of 7.6 ± 0.5 mmHg after a best-case calibration. Conventional PAT was significantly inferior in tracking these changes, with correlation coefficient of −0.60 ± 0.04 and root-mean-squared-error of 14.6 ± 1.5 mmHg (p < 0.05). Scale PTT also tracked the systolic BP changes better than conventional PAT but not to an acceptable level. With further development, scale PTT may permit reliable, convenient measurement of BP.

Wearable Sensing and Telehealth Technology with Potential Applications in the Coronavirus Pandemic

“…The advantage of this method is that the R-peak of the ECG signal is easy to detect, especially during resting conditions. Several studies use alternative cardiac signals for ECG, such as impedance plethysmography (IPG) [99,100], phonocardiogram (PCG) [101,102], or ballistocardiogram (BCG) [103,104]. To improve the user comfort, a peripheral PTT-based multi-wavelength method has been proposed using two or multiple PPG sensors [105][106][107].…”

Multimodal Photoplethysmography-Based Approaches for Improved Detection of Hypertension

“…Kim et al [15] investigated the use of ballistocardiography (BCG) as a replacement for ECG as it does not include the PEP when measured from the BCG-J-wave and can therefore potentially yield a more precise proximal timing reference for PTT. Martin et al [5] later confirmed the accuracy of this method by investigating a bathroom-scale-like device that used BCG and foot PPG waveforms to successfully track BP better than PAT-BP [16].…”

“…Based on the same idea, the pulse arrival time (PAT) is also tested and examined, and both PTT and PAT have been found to be closely correlated with BP [4]. The PTT and PAT durations reflect the time required for an arterial pressure wave to travel between a proximal and a distal site of an artery [5]. The difference being that the PAT includes an initial measurement at the heart, commonly measured using electrocardiography (ECG), whereas the initial measurement site for PTT is located distally, calculated by multi-site photoplethysmography (PPG) [6] or through utilization of other biosignals.…”

A Revised Point-to-Point Calibration Approach with Adaptive Errors Correction to Weaken Initial Sensitivity of Cuff-Less Blood Pressure Estimation

“…For decades, many directions, such as biosensor [7,8], signal processing [9], calibrating, or modeling [10] and performance verification [11] were extensively reported and investigated for cuff-less BP measurement. Various BP monitoring models were proposed based on pulse wave velocity (PWV), pulse transit time (PTT), and pulse wave analysis (PWA), in which pulse signals could be non-invasively obtained through electrocardiogram (ECG), non-invasive photoplethysmography (PPG) [3,8] and ballistocardiography (BCG) originated from a cardiovascular system. Here, PPG, a non-invasive optical measurement technique by means of photoelectric measurement, obtained physiological signals and characteristics of the human body by detecting changes in blood volume in microvessels.…”