Flat knitted sensors for respiration monitoring [From mind to market]

T his article discusses the development and testing of textile electrodes and piezoresistive sensors [1] made of yarn and integrated in firefighter underwear (Figures 1 and 2) to monitor breathing and electrocardiogram (ECG) data. Ubiquitous recording and transmission of human and environmental data in firefighters and victims in the frame of fire or other emergencies is the core of the European integrated project “Proetex” (FP6-2004IST-4-026987). Within this project, several wearable systems are under development: shoes, jacket, underwear for firefighters/rescuers, and a patch for victims for the purpose of triage. In the firefighter’s underwear three parameters have to be monitored: ECG, respiration, and body temperature. Different from monitoring body temperature, which uses chips embedded in the vest, ECG and respiration are monitored using electrodes and piezoresistive sensors made of yarns and realized in a one-step process during fabric production. This technical solution has been chosen to improve wearability, ease of use, and reduce set-up time of the system, without invalidating sensor performance [2]. The present work shows results obtained with the Proetex inner garment, focusing attention on respiration monitoring. Two different methodologies have been used: variation in electrical resistance in a piezoresistive sensor and variation of thorax impedance measured with four textile electrodes [3].