Concept Exploration: Respiratory Rate Monitoring Garment Using Digital Zero-Crossing Detection

Abstract

Measuring respiratory rate is a vital metric for monitoring human health in any setting. Despite its importance for detecting oncoming medical crises, it is often neglected due to the difficulties in accurate measurement. To combat this neglect, a respiratory rate monitoring smart garment was developed that measures breathing rate in real time in a manner that is unobtrusive to the patient. This paper focuses on a concept exploration of a non-invasive wearable garment to measure real time breathing rate using a digital zero-crossing detection signal processing approach. A respiratory rate monitoring garment was developed with a stitched sensor that wraps around the patient’s chest and operates based on the relationship between resistance and displacement. As a person breathes, the chest expands and contracts, displacing the stitched sensor causing a change in resistance that can be measured and then counted as a breath. Unlike current solutions that utilize the fast Fourier transform (FFT) for signal processing of breathing rate, digital zero-crossing detection is used in this garment for improved accuracy and lower computational power. Four participants took part in a total of 15 trials where their normal breathing rate was measured by the stitched sensor and by at least two independent observers. The average sensor breath count was 2.44 breaths below the manually observed breath count. Major contributions to error were due to manual calibration of the sensor, and these discrepancies will be addressed in further prototype development. Despite the error between the sensor and manual breath count, the performance of the garment indicates respiratory rate monitoring in real time is possible, which increases the feasibility of more accurate and frequent respiratory rate monitoring thus increasing the potential for improved patient health.