An 11 μ w, two-electrode transimpedance biosignal amplifier with active current feedback stabilization

Wearable Real-Time Heart Attack Detection and Warning System to Reduce Road Accidents

Heart attack is one of the leading causes of human death worldwide. Every year, about 610,000 people die of heart attack in the United States alone-that is one in every four deaths-but there are well understood early symptoms of heart attack that could be used to greatly help in saving many lives and minimizing damages by detecting and reporting at an early stage. On the other hand, every year, about 2.35 million people get injured or disabled from road accidents. Unexpectedly, many of these fatal accidents happen due to the heart attack of drivers that leads to the loss of control of the vehicle. The current work proposes the development of a wearable system for real-time detection and warning of heart attacks in drivers, which could be enormously helpful in reducing road accidents. The system consists of two subsystems that communicate wirelessly using Bluetooth technology, namely, a wearable sensor subsystem and an intelligent heart attack detection and warning subsystem. The sensor subsystem records the electrical activity of the heart from the chest area to produce electrocardiogram (ECG) trace and send that to the other portable decision-making subsystem where the symptoms of heart attack are detected. We evaluated the performance of dry electrodes and different electrode configurations and measured overall power consumption of the system. Linear classification and several machine algorithms were trained and tested for real-time application. It was observed that the linear classification algorithm was not able to detect heart attack in noisy data, whereas the support vector machine (SVM) algorithm with polynomial kernel with extended time-frequency features using extended modified B-distribution (EMBD) showed highest accuracy and was able to detect 97.4% and 96.3% of ST-elevation myocardial infarction (STEMI) and non-ST-elevation MI (NSTEMI), respectively. The proposed system can therefore help in reducing the loss of lives from the growing number of road accidents all over the world.

An Engineering Perspective of External Cardiac Loop Recorder: A Systematic Review

External cardiac loop recorder (ELR) is a kind of ECG monitoring system that records cardiac activities of a subject continuously for a long time. When the heart palpitations are not the frequent and nonspecific character, it is difficult to diagnose the disease. In such a case, ELR is used for long-term monitoring of heart signal of the patient. But the cost of ELR is very high. Therefore, it is not prominently available in developing countries like India. Since the design of ELR includes the ECG electrodes, instrumentation amplifier, analog to digital converter, and signal processing unit, a comparative review of each part of the ELR is presented in this paper in order to design a cost effective, low power, and compact kind of ELR. This review will also give different choices available for selecting and designing each part of the ELR system. Finally, the review will suggest the better choice for designing a cost effective external cardiac loop recorder that helps to make it available even for rural people in India.

Preliminary results from BCG and ECG measurements in the heart failure clinic

We report on the preliminary deployment of a bathroom scale-based ballistocardiogram (BCG) system for the in-hospital monitoring of patients with heart failure. These early trials provided valuable insights into the challenges and opportunities for such monitoring. In particular, the need for robust algorithms and adapted BCG metric is suggested. The system was designed to be robust and user-friendly, with dual ballistocardiogram (BCG) and electrocardiogram (ECG) capabilities. The BCG was measured from a modified bathroom scale, while the ECG (used as timing reference) was measured using dry handlebar electrodes. The signal conditioning and digitization circuits were USB-powered, and data acquisition performed using a netbook. Four patients with a NYHA class III at admission were measured daily for the duration of their treatment at Stanford hospital. A measure of BCG quality, in essence a quantitative implementation of the BCG classes originally defined in the 1950s, is proposed as a practical parameter.

A 0.09 μW low power front-end biopotential amplifier for biosignal recording

This work presents a biopotential front-end amplifier in which the MOS transistors are biased in subthreshold region with a supply voltage and current of 0.4-0.8 V and 0.23-1.86 μA, respectively, to reduce the system power. Flicker noise is then removed using a chopping technique, and differential interference produced by electrode impedance imbalance is suppressed using a Gm-C filter. Additionally, the circuit is fabricated using TSMC 0.18 μm CMOS technology with a core area of 0.77 × 0.36 mm². With a minimum supply voltage of 0.4 V, the measured SNR and power consumption of the proposed IC chip are 54.1 dB and 0.09μW, respectively.

Noninvasive measurement of physiological signals on a modified home bathroom scale

A commercial bathroom scale with both handlebar and footpad electrodes was modified to enable measurement of four physiological signals: the ballistocardiogram (BCG), electrocardiogram (ECG), lower body impedance plethysmogram (IPG), and lower body electromyogram (EMG). The BCG, which describes the reaction of the body to cardiac ejection of blood, was measured using the strain gauges in the scale. The ECG was detected using handlebar electrodes with a two-electrode amplifier. For the lower body IPG, the two electrodes under the subject's toes were driven with an ac current stimulus, and the resulting differential voltage across the heels was measured and demodulated synchronously with the source. The voltage signal from the same two footpad electrodes under the heels was passed through a passive low-pass filter network into another amplifier, and the output was the lower body EMG signal. The signals were measured from nine healthy subjects, and the average signal-to-noise ratio (SNR) while the subjects were standing still was estimated for the four signals as follows: BCG, 7.6 dB; ECG, 15.8 dB; IPG, 10.7 dB. During periods of motion, the decrease in SNR for the BCG signal was found to be correlated to the increase in rms power for the lower body EMG (r = 0.89, p <; 0.01). The EMG could, thus, be used to flag noise-corrupted segments of the BCG, increasing the measurement robustness. This setup could be used for monitoring the cardiovascular health of patients at home.

Multi-signal electromechanical cardiovascular monitoring on a modified home bathroom scale

A commercially available bathroom scale was modified to enable unobtrusive and robust cardiovascular monitoring in the home. Handlebar electrodes were interfaced to an ultra-low power, two-electrode electrocardiogram (ECG) acquisition circuit providing consistent and clean heartbeat timing information. In addition, the footpad electrodes were used to detect lower-body electromyogram (EMG) and lower-body impedance plethysmogram (IPG) signals using two parallel circuits. The lower-body EMG signal was used as an indication of excessive motion of the subject on the scale. The lower-body IPG signal is related to blood flow through the legs, and will be investigated further in future studies. Finally, the component of bodyweight that varies with time--the ballistocardiogram (BCG) signal--was amplified from the existing strain gauges built into the scale. A preliminary validation was completed on five healthy subjects of varying sizes. The average signal-to-noise ratio (SNR) values computed over all five subjects for the ECG, IPG, and BCG signals were 17.2, 12.0, and 9.0 dB, respectively.