Robust monitoring of vital signs integrated in textile

Abstract

A system is presented that monitors two of the most vital physiological parameters integrated in a wearable textile garment. Emphasis is put on the selection of sensing systems that are mechanically robust to suit the use in clothing. One application is with newborns suffering from an elevated risk for Sudden Infant Death Syndrome (SIDS). Heart and breathing rate are measured by sensing systems implemented on flexible substrates, integrated onto textile. Breathing rate is assessed by extracting accelerometer signals, which can also be used to detect the posture of the baby. The accelerometers have an accuracy of 1 mg and consume less than 2 mA, interface circuit included. Heart rate is assessed through ECG measurement with dry electrodes and a three-stage differential amplifier with a CMRR of 106 dB at 50 Hz. The system operates on a flexible 3.7 V battery and sends its acquired data wirelessly (at 2.4 GHz with a bandwidth of 770 Hz) to a computer, which processes and visualises the two parameters. Processing involves filtering and peak detection algorithms to extract the breathing and heart rate in Matlab. Because the presented work focuses on the two most important vital signs, the system already proves more robust than common home monitoring SIDS applications, typically focusing on a single parameter. Moreover, the use of accelerometers enables a safe and hermetic packaging technique that excludes unwanted interference.