An electrodeless, wearable system for simultaneous monitoring of cardiac and respiratory function

Introduction: Complex interactions inextricably link the pulmonary and cardiovascular systems. It is unsurprising then that chronic diseases such as chronic obstructive pulmonary disease (COPD) and heart failure are prevalent comorbidities affecting a huge proportion of the world population. Distinguishing their overlapping physiological effects is difficult. As a result the ability to monitor both cardiac function and respiration in a non-intrusive manner would be of great benefit to clinicians and researchers alike. To address this need, we have developed an inexpensive wearable solution to monitor both cardiac and respiration volume. Methods: Four electoresistive bands were pre-calibrated and embedded in a t-shirt. A 1mA constant-current source was applied to each band and the applied voltage recorded at 1kHz using a 16-bit ADC. The circumference of each band was calculated and used to estimate sectional volumes as truncated cones. From this data both respiration and cardiac output in ml are extracted. Results: Volume traces clearly display the contribution the top, mid and low sections of the thorax to respiration. Cardiac output volume is also displayed following signal processing to remove the respiration signal. Conclusions: This preliminary work demonstrates that an electroresistive system as described has tremendous potential as a low-cost method of recording both respiration and cardiac output.