Magnetic plethysmograph transducers for local blood pulse wave velocity measurement

Abstract

We present the design of magnetic plethysmograph (MPG) transducers for detection of blood pulse waveform and evaluation of local pulse wave velocity (PWV), for potential use in cuffless blood pressure (BP) monitoring. The sensors utilize a Hall effect magnetic field sensor to capture the blood pulse waveform. A strap based design is performed to enable reliable capture of large number of cardiac cycles with relative ease. The ability of the transducer to consistently detect the blood pulse is verified by in-vivo trials on few volunteers. A duality of such transducers is utilized to capture the local PWV at the carotid artery. The pulse transit time (PTT) between the two detected pulse waveforms, measured along a small section of the carotid artery, was evaluated using automated algorithms to ensure consistency of measurements. The correlation between the measured values of local PWV and BP was also investigated. The developed transducers provide a reliable, easy modality for detecting pulse waveform on superficial arteries. Such transducers, used for measurement of local PWV, could potentially be utilized for cuffless, continuous evaluation of BP at various superficial arterial sites.

Central Blood Pressure Estimation From Distal PPG Measurement Using Semiclassical Signal Analysis Features

“…where SCSA is recovering the signal shape while ignoring peak details when N h = 2 or N h = 3. (c)(d) With N h increasing (between [5,10]), the rest of the signal is also recovered.…”

“…In fact, most researchers use more than two sensors in their research of cuff-less ABP estimation, [9] has reached fairly well accuracy but also requires two sensors. There are works that utilize only one signal, such as [10], however, multiple magnetic sensors need to be placed in order to obtain pulse wave velocity (PWV) signal, hindering their simplicity to use.…”

“…In the recorded samples of some individuals (typically in a patient), the dicrotic notch is not detectable, thus casting doubt on studies where inappropriate PPG signals might result in high errors with unkown effects. [12] develops new methods for estimating BP regardless of the form and shape (appropriate and inappropriate) of PPG signal, but their result falls into grade C in SBP estimation, with BHS standard [13]. Another challenge is that, in studies such as [9] [12], the result slightly exceeds the error boundary of the systolic blood pressure (SBP) requirement [14].…”

Blood Pressure Estimation Using Photoplethysmography Only: Comparison between Different Machine Learning Approaches

“…Another group of researchers introduced the cuffless BP measurement technique using modified normalised pulse volume and heart rate [ 13 ]. Multiple magnetic sensors have also been used to measure pulse wave velocity (PWV) for the estimation of cuffless BP [ 14 ]. Although some of the cuffless BP devices achieved overall acceptable accuracies, the above mentioned algorithms required at least two sensors [ 15 ], making them unsuitable for true wearable applications.…”

Blood Pressure Estimation Using Pulse Transit Time From Bioimpedance and Continuous Wave Radar

“…Although very compact and comfortable, the orientation of the sensor on the neck may result in the Ballistocardiogram appearing as an unwanted signal. A magnetic sensor has been reported in [17], where two magneto-resistive sensors are placed on either side of a permanent magnet. Blood arterial pulsations influence the magnetic field, changing the resistance of the sensors.…”