Resonance Breathing Intervention Opioid Use Disorder

This intervention uses the Camera Heart Rate Variability (CHRV) smartphone application, a resonance breathing app that is available for download to iPhones and Android devices. The CHRV app uses Photoplethysmography (PPG) technology to measure heart rate. PPG is a noninvasive technology that uses a light source (the phone's flashlight) and a photodetector (the phone's camera lens) at the surface of one's skin to measure the volumetric variations of blood circulation. The app also has a timer (to allow the participant to see how long they use the app in each session). The iPhone version of the app also has a breathing pacer (a bar that moves up and down to show the participant when to inhale and exhale). Participants are instructed to initiate a resonance breathing session for at least 5 minutes every day and whenever they experience cravings, feel like they are going to relapse, feel anxious or stressed, or just want to feel calm.