Kick LL: A Smartwatch for Monitoring Respiration and Heart Rate using Photoplethysmography.

With the growing popularity of wearable devices in the consumer space, interest in leveraging this technological platform in the medical field is rising. In this report, we describe a smartwatch capable of measuring respiration and heart rate using photoplethysmography (PPG). The device couples a photosensor, specifically tuned bandpass filters, and frequency content analysis to extract respiration and heart rate from the PPG signal. The results from the experimental device were compared to a commercial chest strap heart rate monitor. Respiratory rate measurements agreed within 1 breath per minute and heart rate measurements agreed within 3-4 beats per minute of the reference device. Furthermore, the device was packaged in an untethered wristwatch allowing for realtime measurements and analysis.