Danielle C. Mathersul

Background
Chronic pain (CP) and PTSD often co-occur, leading to increased symptom severity, anxiety, depression, disability, and opioid use. Reduced cardiac vagal activity (CVA) and emotion regulation (ER) are both observed within these patients, which is indicated to induce heightened anxiety when faced with pain or trauma reminders. Thus, we aim to specifically target CVA via heart rate variability biofeedback (HRVBF), which to our knowledge has yet to be evaluated in comorbid patients exhibiting CP and PTSD. Additionally, via high frequency data sampling, the trajectories of CVA and ER during HRVBF will be assessed, elucidating potential mechanisms driving clinical benefits.

Methods
This study utilises a six-week randomized waitlist control HRVBF intervention, with a three-month follow-up, in a target sample of N=80, diagnosed with CP and PTSD. Based on the role of CVA in pain, PTSD and ER, we hypothesize that HRVBF will improve symptom severity and enhance ER. Daily HRV and ER assessments, as well as laboratory testing of breathing patterns and HRV at multiple time points throughout the intervention allows for in-depth mediation analysis to infer potential causal relationships between CVA and ER during biofeedback.

Discussion
This study aids in developing new treatment protocols for comorbid CP and PTSD. Furthermore, whilst the association between CVA and ER is well documented, causal relationships during HRVBF have thus far not been delineated. The high data sampling approach provides the opportunity to clarify their interaction in the progression of CP and PTSD.