HRV Biofeedback in Pain Patients

This study fulfills the national Veterans Health Administration/Department of Defense (VHA/DoD) Task Force recommendation that complementary, integrative therapies for pain management be provided to Veterans. Chronic pain elicits stress which increases sympathetic output fostering autonomic nervous system imbalance, an overextended stress response, fatigue, depression and insomnia. Heart Rate Variability (HRV) is a measure of the interplay between the sympathetic and parasympathetic nervous systems, and thus is a useful and easily-measured index of autonomic balance that has a relationship to chronic pain effects. HRV biofeedback (HRV-B) is a novel, biobehavioral procedure that restores normal autonomic balance. Through HRV-B, patients increase parasympathetic cardiac output and restore autonomic balance via induction of 'HRV coherence'. The investigators' pilot study indicated that HRV-B produced coherence and alleviated self-reported ratings of chronic pain and stress among Veterans attending the investigators' Pain Clinic. The proposed clinical intervention will further test hypotheses that HRV-B increases HRV coherence, reduces self-reported pain, stress, depression, fatigue, and insomnia, and improves cognition among Veterans with chronic pain.

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 (n=40 each for the HRV-B and sham treatment groups; total N=80 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)

Outcomes will be measured at 4 time points. pre-training; post-training, one week after the 6 weekly treatments are over; at 4 weeks follow-up after post-training, and at an 8-week post-training follow-up (total time of participation is 16 weeks from pre-training to 8 week follow-up).

Furthermore, chronic stress is associated with disrupted circadian rest/activity rhythms and domains of quality of life (QoL) including fatigue, insomnia, and reduced physical and social functioning. Interventions that relieve pain thus represent a novel therapeutic target for normalizing dysfunctional rest/activity rhythms and these QoL domains among pain patients. The investigators are also interested in assessing the effects of HRV-B on cognitive function in pain patients. Thus, the investigators' secondary exploratory objectives are to determine if HRV-B: (1) improves sleep and rest/activity rhythms; (2) alleviates self-reported fatigue and depression; and (3) improves cognitive function (reaction time, attention). Circadian endpoints will be measured as actigraphic parameters of sleep (e.g., duration, efficiency), and rest/activity (e.g., dichotomy index, interdaily stability), and with the Insomnia Symptom Questionnaire (ISQ); fatigue will be assessed using the Multi-Dimensional Fatigue Inventory (MFI), which assesses general physical and mental fatigue and motivation. Depression will be assessed via the Beck Depression Inventory II (BDI-II). Cognitive function will be measured with a cognitive battery comprised of the Paced Auditory Serial Addition Test (PASAT), the Rey Auditory Verbal Learning Test (RAVLT), and the Psychomotor Vigilance Test (PVT).

Proposed Intervention. HRV-B training will follow a previously established, standardized protocol. The primary (HRV coherence, pain, stress) and exploratory outcomes (insomnia, fatigue, depression, cognition). Outcomes will be assessed at 4 time points: pre-training; post-training, one week after the 6 weekly treatments are over; at 4 weeks follow-up after post-training, and at an 8-week post-training follow-up (total time of participation is 16 weeks from pre-training to 8 week follow-up). There will be no HRV-B training at the 8 week follow-up, only assessment. Standardized procedures will characterize HRV coherence and other frequency- or time-domain HRV measures, and validated instruments will be used to assess pain and stress. Wrist actigraphy will characterize insomnia via continuous, 24-hour/day personal monitoring of rest/activity rhythms at 1-week intervals coinciding with the baseline pre-training (baseline), post-training, and 8-week follow-up assessments. The investigators will provide portable data-logging devices for practicing HRV-B at home. Sham intervention subjects will have pulse and respiration monitored but not receive active training; instead they will view a static, relaxing nature picture on a computer screen.

The investigators will control false discovery rates at 5%. Analyses will be based on intent to treat with two-sided tests. The effect of HRV-B on coherence and other HRV variables will be analyzed using linear mixed models for repeated measures data from sequential time assessments, and a between-subjects factor to evaluate the intervention after adjusting for potential confounding factors (e.g., age, standard therapy, medications, co-morbid disease). Baseline relationships between HRV and endpoints will be examined using multiple regression models. Few studies have examined the multivariate relationship between pain, autonomic dysfunction, stress, depression, sleep, rest/activity rhythms, fatigue, and cognition.