The effect of Spinal Manipulative Therapy on Heart Rate Variability and pain in patients with chronic neck pain: A Randomized Controlled trial

Abstract

Background Recent experimental research has suggested that Spinal Manipulative Therapy (SMT) may reduce pain through modulation of the ascending pain signals and/or the central pain regulating mechanisms. People with persistent neck pain (NP) have also been found to have disturbances in Autonomic Nervous System (ANS) regulation. A common way to study ANS is to measure heart rate variability (HRV). It is not known if deviations in HRV are related to changes in pain perception or to the treatment response to SMT. Commonly, an individual in pain will experience pain reduction when exposed to a second pain stimulus, a mechanism known as Conditioning Pain Modulation (CPM). Patients with persistent pain have been found to have a reduced CPM reaction. It is not known if this is predictive of treatment response to SMT. The aim of the study is to examine the effects of SMT on HRV and pain and to test if a CPM test can be used to predict treatment response, in a population of patients with recurrent and persistent NP. Method/Design A multicentre randomized controlled clinical trial will be carried out in multidisciplinary primary care clinics. This setting is chosen to minimize bias resulting from patient preference to treatment modality and provider. The subjects are either self-referred or referred from other health care practitioners locally. The treatment modalities are two well-known interventions for NP; SMT and stretching exercises compared to stretching exercises alone. The subjective pain experience will be investigated by assessing pain intensity and the affective quality of pain. HRV will be measured using a portable heart monitor and CPM will be measured with a standardized cold-pressor-test. Measurements will be performed at baseline, prior to the third treatment and after the fourth treatment. Discussion The study will utilize normal clinical procedures, which should aid transferability and external validity of the results. The study will provide knowledge regarding the underlying mechanisms of the effects of SMT. Furthermore, the study will examine if a CPM test is predictive of treatment outcome in a population of patients with recurrent and persistent NP.