A Wearable Biofeedback Intervention Device for Continuous Stress Monitoring with Pulse Transit Time Measurement

Abstract

Stress can lead to increased vulnerability to disease and is important for management of recovery for substance use disorder. Stress can determined by pulse transit time(PTT) within a physiological monitoring system, using both electrocardiogram and pulse waves. Pulse transit time is the time difference between the R peak in the ECG wave and the start of the pulse. Recovering patients exhibit stress when facing cues, so a biofeedback system would recognize this stress and train the user with a relaxation method. The system is intended to be portable with three electrodes located near the center of the chest. An Arduino was connected to a custom ECG and a pulse sensor worn on the wrist that used photoplethysmography. The pulse sensor had noise when there was wrist movement. Chest movement and heavy breathing shifted the baseline of the QRS complex. Both had small fluctuations which were reduced by a smoothing filter. Pulse Transit Time can be calculated and monitored live, displayed on a screen warning the user of stress. For accuracy, the monitoring system needs to be checked. When a cue is detected, the user is aware of stress and the monitor is able to provide a relaxation tool, so that less stress is induced the next time a cue is present.