Clinical Evaluation of Stretchable and Wearable Inkjet-Printed Strain Gauge Sensor for Respiratory Rate Monitoring at Different Body Postures

Abstract

Respiratory rate (RR) is a vital sign with continuous, convenient, and accurate measurement which is difficult and still under investigation. The present study investigates and evaluates a stretchable and wearable inkjet-printed strain gauge sensor (IJP) to estimate the RR continuously by detecting the respiratory volume change in the chest area. As the volume change could cause different strain changes at different body postures, this study aims to investigate the accuracy of the IJP RR sensor at selected postures. The evaluation was performed twice on 15 healthy male subjects (mean ± SD of age: 24 ± 1.22 years). The RR was simultaneously measured in breaths per minute (BPM) by the IJP RR sensor and a reference RR sensor (e-Health nasal thermal sensor) at each of the five body postures namely standing, sitting at 90°, Flower’s position at 45°, supine, and right lateral recumbent. There was no significant difference in measured RR between IJP and reference sensors, between two trials, or between different body postures (all p > 0.05). Body posture did not have any significant effect on the difference of RR measurements between IJP and the reference sensors (difference <0.01 BPM for each measurement in both trials). The IJP sensor could accurately measure the RR at different body postures, which makes it a promising, simple, and user-friendly option for clinical and daily uses.

Influences of Sensor Placement Site and Subject Posture on Measurement of Respiratory Frequency Using Triaxial Accelerometers

“…It has been proven that with a gap longer than 10 min, there was significant difference (>30% of measured value) between repeated measurements of RF ( Edmonds et al, 2002 ). In our parallel study, with the gap of 1 min, there was no significant difference between repeated measurements of RF ( Al-Halhouli et al, 2020 ). Therefore, we used the gap of 2 min to ensure the repeatability of the RF measurements while the subjects could have a good rest.…”

Wearable Sensing and Telehealth Technology with Potential Applications in the Coronavirus Pandemic

“…The sensor technologies include thermal, humidity, acoustic, pressure, resistive, inductive, acceleration, electromyography, and impedance. A wearable device with these sensors can be mounted into chest belts, attached to a chest belt [40][41][42][43], or applied to the skin [44,45], amongst other modes of attachment.…”

“…But monitoring with a face mask can still be intrusive to users, and the displacement of the sensor may affect the accuracy. [47], RespiraSense™ patch (PMD Solutions, Ireland) [48], and MonBaby clip (MonBaby, New York, USA) [49], (b) Zephyr™ garment (Zephyr Technology, Auckland, New Zealand) [50], and state-of-the-art research (c) an epidermal thermal sensor [45], (d) humidity sensor [46], (e) wearable strain gauge [41], (f) waist-wearable triboelectric sensor, (g) breathing belt with 3D accelerometer [42], and (h) a BandAid like respiratory monitor [44].…”

“…The results indicate a high RR estimation accuracy (<0.07±0.54 bpm) at these places without significant difference, but the upper thorax was shown to be the most comfortable location [41]. Zhang et al developed a triboelectric nanogenerator based waist-wearable wireless respiratory monitoring device, and it was demonstrated to be highly accurate and sensitive for realtime respiratory monitoring [40].…”

Flexible ferroelectric wearable devices for medical applications

“…Al-Halhouli et al. used the inkjet printing technique to develop a stretchable and wearable strain gauge sensor (gauge factor >100) which could accurately measure the respiratory volume change in the chest area at five different postures; this included standing, sitting at 90°, Fowler's position at 45°, supine and right lateral recumbent ( Al-Halhouli et al., 2020 ).…”