Heart rate variability (HRV) is among the most promising markers for the detection of mental stress. HRV represents the variations in the beat-to-beat alteration in the heart rate.

We have realized a prototype system based on a custom sensor board (named CardioShield) with a specific receiver for a wireless chest belt (produced by Polar Electro) detecting heart beats. The board is mounted on a standard TelosB mote running
SPINE, customized with a specific processing function that computes the inter-beat time interval.

The prototype running on the SPINE coordinator receives these timed events and performs an HRV analysis by extracting time-domain features on the inter-beat times over a 10-min window. Then, these features are fed to a threshold-based classifier to detect the mental stress condition of the subject.

Reference paper

A. Andreoli, R. Gravina, R. Giannantonio, P. Pierleoni, and G. Fortino. SPINE-HRV: a BSN-based toolkit for heart rate variability analysis in the time-domain. Wearable and Autonomous Biomedical Devices and Systems: New issues and Characterization – Lecture Notes on Electrical Engineering, 75:369-389, 2010.