Touch-Based System for Beat-to-Beat Impedance Cardiogram Acquisition and Hemodynamic Parameters Estimation
Among all cardiovascular diseases, congestive heart failure (CHF) has a very high rate of hospitalization and mortality. In order to prevent hospitalization, there is a strong need to identify patients at risk of a CHF event by estimating a set of relevant hemodynamic parameters that will allow physicians to detect its early onset. Today, one of the most popular non-invasive methods to obtain these parameters is through the acquisition of electrocardiogram (ECG) and impedance cardiogram (ICG) by using large hospital systems with electrodes placed on the chest and thorax region. In order to be useful in an ambulatory setting, it is important to obtain an ultra-low power wearable system for acquiring the ICG and ECG, and to detect CHF. In this paper, we present a touch-based ultra-low power device for real-time ICG and ECG signal acquisition, and hemodynamic parameters estimation. We also propose methods for noise cancellation and for calculating the hemodynamic parameters. In addition, a comparative evaluation of susceptibility to different measuring positions is presented. Our proposed design is highly correlated with traditional systems (> 80%), but able to work with very low power budgets, thus allowing long duration of over four days on a single battery charge.