Design and preliminary assessment of a smart textile for respiratory monitoring based on an array of Fiber Bragg Gratings

Abstract

Comfortable and easy to wear smart textiles have gained popularity for continuous respiratory monitoring. Among different emerging technologies, smart textiles based on fiber optic sensors (FOSs) have several advantages, like Magnetic Resonance (MR)-compatibility and good metrological properties. In this paper we report on the development and assessment of an MR-compatible smart textiles based on FOSs for respiratory monitoring. The system consists of six fiber Bragg grating (FBG) sensors glued on the textile to monitor six compartments of the chest wall (i.e., right and left upper thorax, right and left abdominal rib cage, and right and left abdomen). This solution allows monitoring both global respiratory parameters and each compartment volume change. The system converts thoracic movements into strain measured by the FBGs. The positioning of the FBGs was optimized by experiments performed using an optoelectronic system. The feasibility of the smart textile was assessed on 6 healthy volunteers. Experimental data were compared to the ones estimated by an optoelectronic plethysmography used as reference. Promising results were obtained on both breathing period (maximum percentage error is 1.14%), inspiratory and expiratory period, as well as on total volume change (mean percentage difference between the two systems was ~14%). The Bland-Altman analysis shows a satisfactory accuracy for the parameters under investigation. The proposed system is safe and non-invasive, MR-compatible, and allows monitoring compartmental volumes.

Sensing Systems for Respiration Monitoring: A Technical Systematic Review

“…It was the most widely used parameter by far. Other metrics based on the analysis of the magnitude versus time curve, such as breathing period or expiratory/inspiratory times, were barely used (2% in the wearable category) [ 94 , 103 ]. The representation of the volume versus time curve or the use of volumetric parameters was not common.…”

“…In relation to the activities or positions considered in the experiments, lying down and sitting were the most tested positions. Other positions or activities, like standing, walking, moving, or running, were used in a minority of studies [ 2 , 17 , 21 , 61 , 62 , 66 , 67 , 68 , 77 , 79 , 81 , 91 , 94 , 101 , 102 , 103 , 108 , 110 , 111 , 115 , 118 , 119 , 124 , 129 , 131 , 132 , 135 , 146 , 147 , 148 , 149 , 177 , 178 , 188 , 205 , 214 , 233 , 235 ]. Most of the studies that provided information on activities considered more than one position [ 2 , 6 , 9 , 17 , 21 , 52 , 53 , 61 , 62 , 66 , 67 , 68 ,…”

“…Maximum-minimum detection: A popular processing technique is to identify maximum and/or minimum points in the breathing signals ( x ). Massaroni et al [ 103 ] used the maximum and minimum values to obtain the respiratory period ( T r ), as well as inspiratory ( T i ) and expiratory ( T e ) time. The process for detecting maximum and minimum points is similar to peak detection.…”

“…Other parameters, such as size or weight, can also affect the adoption of the technology. These parameters have only been provided in a limited number of studies [ 2 , 3 , 17 , 21 , 49 , 62 , 64 , 68 , 72 , 85 , 93 , 94 , 97 , 98 , 99 , 103 , 105 , 108 , 110 , 113 , 114 , 116 , 119 , 120 , 124 , 126 , 135 , 136 , 138 , 141 , 143 , 144 , 146 , 148 , 161 ]. Future works should also consider size and weight as important factors in the design of sensing systems, subjecting them to evaluation.…”

“…An ideal breathing sensor should be mobile, easy to use, imperceptible and immune to body motion [ 48 , 119 , 135 ]. Several authors agree that a system that covers all these aspect should be successfully integrated into clothing [ 21 , 59 , 65 , 69 , 84 , 85 , 94 , 103 , 108 , 113 , 119 , 123 , 142 , 143 , 151 ]. This is a consequence of the fact that long-term home monitoring entails direct connection between patient and system.…”