Detecting Respiratory Rate Using Flexible Multimaterial Fiber Electrodes Designed for a Wearable Garment

Smart sensors embedded into wearables and capable of monitoring vital signs have become an important research topic and the technology of interest for numerous commercial ventures. Monitoring respiratory rate is challenging due to the complexity and uniqueness of the musculoskeletal movements involved in the breathing process. At the same time, it is a critical factor in assessing patient health. Multi-material fibers exhibit the potential to be inter-woven into a textile and used in a wearable garment to measure respiration rate. This study compares the effectiveness of two types of flexible multi-material fibers, namely the polyethylene-co-vinyl acetate (PEVA) fiber and the polydimethylsiloxane elastomer (PDMS) fiber, in detecting respiratory rate using two principles, the Fiber Strain method and the Bioimpedance method. The study involved five experiments where ten volunteers' respiratory rate was measured under different conditions: deep breathing, holding breath, deep breathing with exercise, relaxed breathing, and deep breathing with the fibers mounted onto a wearable. Overall, the PDMS fiber outperformed the PEVA fiber in detecting the breathing rate by providing better accuracy, greater signal to noise ratio (SNR), and more versatility. Although some studies have previously described the successful use of multi-material fibers in monitoring vital signs, e.g., electromyography, no reported research could be identified that examined the use of these multi-material fibers for respiratory rate measurement.