Towards the standardization of ballistocardiography systems for J-peak timing measurement

Abstract

Ab st ra c t -There is a growing interest in accurately measuring the timing of the J peak of the ballistocardiogram (BCG) in order to obtain cardiovascular function markers non-invasively, especially in modern home healthcare applications. In this paper we have studied the effect that some common uncertainty sources have in the time measurement of the J peak. This is a necessary step towards the standardization of modern ballistocardiography systems equivalent to that available for EGC systems. We conclude that, to reduce J peak time uncertainty below the measured intrinsic uncertainty of about ±2 ms, the minimal bandwidth should be from 1.5 Hz to 22.5 Hz; the sampling frequency can be decreased up to 50 Hz when using cubic spline interpolation; 5 bits are required to quantify the signal, and signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR) should be over 40 dB and 3 dB respectively. Ke ywo rd s: Ballistocardiogram, acquisition system, biomedical instrumentation, standardization.

Direct Pulse Transit Time Measurement from an Electronic Weighing Scale

“…The four strain gages in an electronic weighing scale were connected into a Wheatstone bridge and interfaced to a differential amplifier with gain set to 5,000 by using a fully-differential, first-order, high-pass, passive filter [16], with corner frequency set to 0.5 Hz [17] to reject the body weight signal and low-frequency motion artifacts. The amplifier output was ac-coupled to an amplifier with gain 5 and corner frequency set to 0.5 Hz whose output was connected to a first-order, low-pass filter with corner frequency set to 25 Hz [17] to reduce high-frequency noise and power-line interference.…”

Impact of the Mechanical Interface on BCG Signals obtained from Electronic Weighing Scales

“…The BCG was obtained from each scale by arranging their strain gauges to form a Wheatstone bridge that was connected to a typical BCG analog front-end [9]. This provided a total gain of 25,000 and a bandwidth from 0.5 Hz to 25 Hz that minimizes possible errors in the timing of BCG waves [9].…”

“…This provided a total gain of 25,000 and a bandwidth from 0.5 Hz to 25 Hz that minimizes possible errors in the timing of BCG waves [9].…”

“…Additionally, a lead I ECG was recorded between hands by using a custom ambulatory ECG system [9], to be used as a timing reference during the analysis of BCG data.…”

“…This view, in which the mechanic response of the weighing scale is considered not to distort the BCG signal, has been sustained until now [1,8]. Contrarily, the influence of the electronic interface has received more attention as a necessary step towards the standardization of electronic stages of BCG acquisition systems [9]. On the other hand, it has been recently pointed out that time correlations between the pre-ejection period and some features of the BCG are different when measured using a force plate or a weighing scale [10], which has been attributed to the wider bandwidth of force plates.…”