 The specific aims are to: 1 conduct a randomized, sham-controlled, pilot intervention trial to determine whether HRV-B increases HRV coherence among chronic pain patients n40 each for the HRV-B and sham treatment groups; total N80 patients; 2 determine whether HRV-B reduces self-reported pain and stress among chronic pain patients. The primary endpoints include HRV coherence, pain Brief Pain Inventory or BPI,and stress Perceived Stress Scale or PSS 