P.-F. Migeotte is with the Department of Cardiology, Universite Libre de Bruxelles 1050, Brussels, Belgium (e-mail: Pierre-Francois.Migeotte@ulb.ac.be).K.-S. Park is with the Department of Biomedical Engineering, Seoul National University, Seoul 110-799, Korea (e-mail: kspark@bmsil.snu.ac.kr).M. Etemadi is with the Department of Bioengineering and Therapeutic Sciences, University of California at San Francisco, San Francisco, CA 94143 USA (e-mail: mozziyar.etemadi@ucsf.edu).K. Tavakolian is with the Department of Electrical Engineering, University of North Dakota, Grand Forks, ND 58202 USA (e-mail: kouhyart@gmail.com).R. Casanella is with the Instrumentation, Sensors, and Interfaces Group, Universitat Politecnica de Catalunya, 08034 Barcelona, Spain (e-mail: ramon. casanella@upc.edu).J. Zanetti is with Acceleron Medical Systems, Arkansaw, WI 54721 USA (e-mail: jmzsenior@gmail.com).J. Tank is with the Klinsche Pharmakologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany (e-mail: Tank.Jens@mh-hannover.de).I. Funtova is with the

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This paper describes a novel differential synchronous demodulator intended for signal conditioning in modulating sensors and impedance measurements. The circuit proposed merges the demodulating and low-pass filtering stages in a single integrator stage and yields, for differential measurements, the performance quality inherent to coherent demodulation, with the added advantages of compactness and low cost. We analyse the theoretical limits of the relevant performance parameters, such as the common mode rejection ratio (CMRR), signal-to-noise ratio (SNR), linearity and quadrature rejection. Our experimental results validate the theoretical predictions. In the range from 1 kHz to 50 kHz, the CMRR, which does not depend on matching integrating capacitors, exceeds 65 dB for unity differential gain, and the SNR exceeds 90 dB.

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.

Ballistocardiography is a non-invasive technique that yields information about the cardiovascular system that is not available in other external signals such as the electrocardiogram (ECG). In the last years, several research groups have obtained the ballistocardiogram (BCG) by using instrumentation methods simpler than those available in the 1950s and that did not progress because of their complexity as compared to ultrasound and other noninvasive techniques that are in common use nowadays. We describe a novel method for real-time robust heart- (HR) and respiratory- (RR) rate detection from a subject that stands on a common electronic bathroom scale. BCG signals from the scale are wirelessly sent to a PC where algorithms based on the continuous wavelet transform (CWT) extract the HR and the RR. HR results are compared to those obtained from the ECG. To better assess the RR results, subjects have been asked to synchronize their breathing rate to an on-screen bar-graph set at a constant rate of breaths per minute. This method to obtain the heart and respiratory rates is simple, compact, non-invasive and passive, and can be applied to any person able to stand on an electronic weighing scale, even if wearing shoes.

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Time intervals measured between the electrocardiogram (ECG), the photoplethysmogram (PPG) or the impedance plethysmogram (IPG), have long been used to noninvasively assess cardiovascular function. Recently, the ballistocardiogram (BCG) has been proposed as an alternative physiological signal to be used in time interval measurements for the same purpose. In this work, we study the behavior of the RJ interval, defined as the time between the R wave of the electrocardiogram (ECG) and the J wave of the BCG, under fast pressure changes induced by paced respiration and tracked by a beat-to-beat blood pressure (SBP and DBP) waveform monitor. The aim of this work is to gain a deeper understanding of these newly proposed time intervals and to further assess their usefulness to determine cardiovascular performance.

The Driven-Right-Leg (DRL) circuit has been used for about 50 years to reduce interference due to common-mode voltage in biopotential amplifiers in scenarios that range from fixed equipment supplied from power lines to battery-supplied ambulatory monitors, and for systems that use gelled, dry, textile, and capacitive electrodes. However, power-line interference models predict that for isolation amplifiers, currently mandated by safety standards, power-line interference can often couple mostly in differential mode rather than in common mode. In this work we analyze the effect of the DRL circuit in different ECG leads to elucidate its actual effect on power-line interference reduction. It turns out that that the DRL circuit, which effectively reduces common-mode interference, affects differential-mode interference in an unpredictable way and can increase interference.