A Textile Sleeve for Monitoring Oxygen Saturation Using Multichannel Optical Fibre Photoplethysmography.

Hattan K Ballaji,Stephen P Morgan,Serhiy Korposh,Francisco U Hernandez,Byron Salisbury,Ricardo Correia,Barrie R Hayes-Gill

doi:10.3390/s20226568

Hattan K Ballaji, Stephen P Morgan + Show 5 more

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https://doi.org/10.3390/s20226568

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Abstract

Textile-based systems are an attractive prospect for wearable technology as they can provide monitoring of key physiological parameters in a comfortable and unobtrusive form. A novel system based on multichannel optical fibre sensor probes integrated into a textile sleeve is described. The system measures the photoplethysmogram (PPG) at two wavelengths (660 and 830 nm), which is then used to calculate oxygen saturation (SpO2). In order to achieve reliable measurement without adjusting the position of the garment, four plastic optical fibre (POF) probes are utilised to increase the likelihood that a high-quality PPG is obtained due to at least one of the probes being positioned over a blood vessel. Each probe transmits and receives light into the skin to measure the PPG and SpO2. All POFs are integrated in a stretchable textile sleeve with a circumference of 15 cm to keep the sensor in contact with the subject’s wrist and to minimise motion artefacts. Tests on healthy volunteers show that the multichannel PPG sensor faithfully provides an SpO2 reading in at least one of the four sensor channels in all cases with no need for adjusting the position of the sleeve. This could not be achieved using a single sensor alone. The multichannel sensor is used to monitor the SpO2 of 10 participants with an average wrist circumference of 16.0 ± 0.6 cm. Comparing the developed sensor’s SpO2 readings to a reference commercial oximeter (reflectance Masimo Radical-7) illustrates that the mean difference between the two sensors’ readings is −0.03%, the upper limit of agreement (LOA) is 0.52% and the lower LOA is −0.58%. This multichannel sensor has the potential to achieve reliable, unobtrusive and comfortable textile-based monitoring of both heart rate and SpO2 during everyday life.

Highlights

Wearable and smart textile technology for health monitoring is an area of great interest for health and wellbeing
This paper describes the first implementation of a textile-based multichannel SpO2 measurement system and an investigation in a human volunteer study
Sensor C did not provide any PPG signals. This 100% reliable PPG detection was possible in all 10 subjects. These results demonstrate that sensor position is important for obtaining high quality PPG signals, and this is likely to be related to whether the sensor lies near a major vessel

Summary

Introduction

Wearable and smart textile technology for health monitoring is an area of great interest for health and wellbeing. New devices have been developed using different sensing technology with the aim of providing reliable unobtrusive monitoring [1,2,3,4]. These devices use discrete sensors integrated into textiles and there are challenges with comfort of users for long-term health monitoring. Sensors 2020, 20, 6568 fibres into textiles [5,6,7,8,9] where heart rate and oxygen saturation monitoring have been demonstrated. Photoplethysmography (PPG) technology is used extensively in optical sensors that are found in medical and fitness monitoring devices. Red and infrared (IR) wavelengths are typically combined to calculate an R value [12,13]: R=

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