Polymer Optical Fibre Sensor for Measuring Breathing Rate of Lying Person

Abstract

Abstract A physiological sensor enabling measurement of one of the vital signs (breathing rate) of a person without direct contact with the person is presented. Compared to current vital signs measuring devices we present a much simpler and less time consuming method of measuring vital signs with the potential for applications in hospitals and homes. A practical prototype sensor, based on polymer optical fibre (POF) sensor instrumentation was fabricated using Toray specific grade fibre exhibiting an increase in 30 % bending losses from the standard (FX 1000) commercial fibre. A 640 nm light-emitting diode was used to illuminate the fibre, with its sensitivity to bending increased by cutting transversal grooves along the fibre and then by applying plastic rods along the fibre to increase bending loss. Although both methods increased the bending loss of the fibre, grooving reduced POF durability and integrity, whereas use of the plastic rods enhanced bending losses without damaging the fibre. Signals from respiration as well as postural movements of a person lying on the POF sensor allow measurements to be taken in an unobtrusive manner. Bending losses attenuating light transmission through the fibre were related to displacement of POF during respiration (expansion and contraction of the chest cavity displace the surface in contact with the upper torso – in this case the meandering arrangement of the fibre sensor located on a TREDAIRE substrate). Bending losses were converted to voltage signals and captured by National Instruments hardware together with LabVIEW software. The sensor was found to be competent in evaluating respiration with a resolution of 100 μV and a sensitivity of 2.3 % change in light transmission for each breathing cycle of the person under study.