Meta-analytic evidence for decreased heart rate variability in chronic pain implicating parasympathetic nervous system dysregulation

Effects of spinal cord stimulation on heart rate variability in patients with Failed Back Surgery Syndrome

Background

Building on the recent finding that chronic pain patients with impaired functioning of the descending nociceptive inhibitory system (DNIS) present lower resting heart rate variability (HRV), this study aims to investigate the impact of Spinal Cord Stimulation (SCS) on HRV in patients with Failed Back Surgery Syndrome (FBSS). More precisely, we hypothesize that SCS influences the DNIS, with increased parasympathetic tone as a consequence, as measurable by HRV analysis.

Methods

Twenty-two patients diagnosed with FBSS and treated with SCS participated in this study. HRV was measured with a 2-lead ECG registration tool during on and off states of SCS. HRV analysis for time, frequency, time-frequency and nonlinear domain parameters was based on a 5-minute recording segment.

Results

The mean heart rate and low frequency power were significantly lower when SCS was activated. HRV, absolute and normalized high frequency power significantly increased during SCS compared to without SCS. The ratio of low frequency/high frequency ratios, as parameter for global sympathetic-parasympathetic equilibrium, significantly decreased when SCS was activated.

Conclusions

When SCS is switched off, patients with FBSS present relatively stronger sympathetic tone and weaker parasympathetic activity. Activation of the SCS, possibly via stimulation of the DNIS, restores this disbalance of autonomic activity.

Machine learning-based prediction of clinical pain using multimodal neuroimaging and autonomic metrics

Although self-report pain ratings are the gold standard in clinical pain assessment, they are inherently subjective in nature and significantly influenced by multidimensional contextual variables. Although objective biomarkers for pain could substantially aid pain diagnosis and development of novel therapies, reliable markers for clinical pain have been elusive. In this study, individualized physical maneuvers were used to exacerbate clinical pain in patients with chronic low back pain (N = 53), thereby experimentally producing lower and higher pain states. Multivariate machine-learning models were then built from brain imaging (resting-state blood-oxygenation-level-dependent and arterial spin labeling functional imaging) and autonomic activity (heart rate variability) features to predict within-patient clinical pain intensity states (ie, lower vs higher pain) and were then applied to predict between-patient clinical pain ratings with independent training and testing data sets. Within-patient classification between lower and higher clinical pain intensity states showed best performance (accuracy = 92.45%, area under the curve = 0.97) when all 3 multimodal parameters were combined. Between-patient prediction of clinical pain intensity using independent training and testing data sets also demonstrated significant prediction across pain ratings using the combined model (Pearson's r = 0.63). Classification of increased pain was weighted by elevated cerebral blood flow in the thalamus, and prefrontal and posterior cingulate cortices, and increased primary somatosensory connectivity to frontoinsular cortex. Our machine-learning approach introduces a model with putative biomarkers for clinical pain and multiple clinical applications alongside self-report, from pain assessment in noncommunicative patients to identification of objective pain endophenotypes that can be used in future longitudinal research aimed at discovery of new approaches to combat chronic pain.

Correlation Between Chronic Neck Pain and Heart Rate Variability Indices at Rest: A Cross-sectional Study

OBJECTIVE

The purpose of this study was to correlate the heart rate variability (HRV) indices with variables of pain that were experienced by individuals with chronic neck pain.

METHODS

This was a blinded cross-sectional study. Individuals with chronic neck pain (n = 15) and healthy participants (n = 15), both sedentary and between 18 and 45 years of age, were included. The neck pain was assessed with the Numerical Rating Scale at rest and during cervical movements, Neck Disability Index, Catastrophic Thoughts about Pain Scale, and Tampa Scale of Kinesiophobia. The HRV indices (linear and nonlinear) were used for assessment of autonomic function at rest (in supine, sitting, and standing positions).

RESULTS

We observed significant correlations between the NRS, Neck Disability Index, and Catastrophic Thoughts about Pain Scale with the linear and nonlinear HRV indices (P < .05, r ≥ 0.362), so that the worst HRV indices are associated with conditions of more intense and disabling neck pain.

CONCLUSION

The HRV indices were significantly associated with pain intensity, disabilty, and catastrophizing in individuals with chronic neck pain.

Efficacy of risk stratification protocols and clinical, physical, and biochemical parameters to previse signals and symptoms during cardiovascular rehabilitation programs: Protocol for an observational trial

INTRODUCTION

Despite the benefits, cardiovascular rehabilitation programs (CRPs) have been related to the appearance of signals and symptoms. Risk stratification protocols are commonly used to identify risks during the physical exercise; however, studies that investigate their efficacy to previse signals and symptoms are inconclusive. Furthermore, clinical, physical, and biochemical parameters have been used as risk markers for the appearance of adverse events, and to investigate their efficacy to previse signals and symptoms during the CRP sessions that could better guide the strategies adopted on these programs.

OBJECTIVES

The aim of this study was to evaluate the correlations between risk stratification protocols and clinical, physical, and biochemical parameters with the appearance of signals/symptoms during CRP, as well as to evaluate if modifications on clinical, physical, and biochemical parameters could influence in the appearance of signals/symptoms during CRP.

MATERIALS AND METHODS

The study was prospectively registered at ClinicalTrials.gov (NCT03446742). Forty-four patient participants of a CRP will be evaluated. First, their risk stratification is going to be performed by 2 evaluators and their clinical, physical, and biochemical parameters are going to be measured. Then, the patients are going to be followed during 24 sessions during their CRP routines in order to identify appearance of their signals/symptoms. So, the patients are going to perform their cardiovascular rehabilitation routines for 6 months and then, their clinical, physical, and biochemical parameters are going to be measured again and they are going to be followed during 24 sessions during their CRP routines in order to identify the appearance of their signals/symptoms.

Chronic pain-related changes in cardiovascular regulation and impact on comorbid hypertension in a general population: the Tromsø study

Heart rate variability (HRV) and baroreflex sensitivity (BRS) are indexes reflecting the ability to maintain cardiovascular homeostasis amidst changing conditions. Evidence primarily from small studies suggests that both HRV and BRS may be reduced in individuals with chronic pain (CP), with potential implications for cardiovascular risk. We compared HRV and BRS between individuals with CP (broadly defined) and pain-free controls in a large unselected population sample. Participants were 1143 individuals reporting clinically meaningful CP and 5640 pain-free controls who completed a 106-second cold pressor test (CPT). Participants self-reported hypertension status. Resting HRV and BRS were derived from continuous beat-to-beat blood pressure recordings obtained before and after the CPT. Hierarchical regressions for the pre-CPT period indicated that beyond effects of age, sex, and body mass index, the CP group displayed significantly lower HRV in both the time domain (SDNN and rMSSD) and frequency domain (high-frequency HRV power), as well as lower BRS. Results were somewhat weaker for the post-CPT period. Mediation analyses indicated that for 6 of 7 HRV and BRS measures tested, there were significant indirect (mediated) effects of CP status on the presence of comorbid hypertension via reduced HRV or BRS. Results confirm in the largest and broadest sample tested to date that the presence of CP is linked to impaired cardiovascular regulation and for the first time provide support for the hypothesis that links between CP and comorbid hypertension reported in previous population studies may be due in part to CP-related decrements in cardiovascular regulation.

The acute effects of joint manipulative techniques on markers of autonomic nervous system activity: a systematic review and meta-analysis of randomized sham-controlled trials

Background

The autonomic nervous system (ANS) interests many chiropractors and manual therapists, because joint manipulative techniques (JMT), e.g. high velocity low amplitude (HVLA) manipulations and mobilizations, appear to produce acute changes in ANS mediated physiology. The complexity of this issue justifies a systematic critical literature review.

Objective

To review the literature comparing the acute changes in markers of ANS activity between JMT applied on spinal or peripheral joints and a sham procedure in healthy or symptomatic subjects.

Method

We searched PsycINFO, PEDro, PubMed, Cochrane library, EMBASE, and Medline up to December 2017. We updated the search with PubMed, Cochrane library, EMBASE, and Medline including July 2018. Inclusion criteria were: randomized sham-controlled trials assessing the effect of JMT on markers of ANS activity; manually applied JMT, regardless of technique, applied on either healthy or symptomatic humans; outcome measurements recorded at baseline and repeated during and/or after interventions. Selection of articles and data extraction were performed independently by two reviewers. The quality of studies was assessed using the Cochrane ‘risk of bias’ tool and a technical check-list. Results were reported narratively with some meta-analyses. The Cochrane GRADE approach was used to assess the certainty of evidence.

Results

Twenty-nine of 2267 studies were included in the synthesis. Mobilizations (oscillatory technique) probably produce an immediate and short-term, bilateral increase in skin sympathetic nerve activity (reflected by an increase in skin conductance) regardless of the area treated (moderate-certainty evidence). It is uncertain whether the sympathetic arousal also explains an increase in respiratory rate (very low-certainty evidence). Our evaluation of the literature suggests that spinal sustained apophyseal glides (SNAGs) mobilization and HVLA manipulation of the spine may have no acute effect on the studied markers of ANS activity (very low- to low-certainty evidence).

Conclusion

Some types of mobilizations probably produce an immediate and short-term, statistically significant increase in skin sympathetic nerve activity when compared to a sham procedure, whereas spinal SNAGs and spinal HVLA techniques may have no acute effect on the studied markers of ANS activity. No region-specific results were noted. The literature suffers from several shortcomings, for which reason we strongly suggest further research.

Electronic supplementary material

The online version of this article (10.1186/s12998-019-0235-1) contains supplementary material, which is available to authorized users.

Musculoskeletal pains and cardiovascular autonomic function in the general Northern Finnish population

BACKGROUND

Heart rate variability (HRV) and baroreflex sensitivity (BRS) measurements provide means for the objective assessment of cardiovascular autonomic function. As previous studies have associated chronic pain with abnormal autonomic function, we aimed to characterize the relationship between the number of musculoskeletal pain sites (NPS), pain intensity, and cardiovascular autonomic function among the population-based Northern Finland Birth Cohort 1966.

METHODS

At the age of 46, cohort members self-reported their musculoskeletal pains (enabling the determination of NPS [0-8] and pain intensity [Numerical Rating Scale, NRS, 0-10]) and underwent clinical assessments of cardiovascular autonomic function in seated and standing positions (HRV variables: heart rate [HR] and root mean square of successive differences in beat-to-beat intervals [rMSSD] for the entire cohort; BRS variables: low-frequency systolic blood pressure variability [SBPV] and cross-spectral baroreflex sensitivity [BRS] for those attending the examination in Oulu, Finland). Extensive confounder data were also collected (body mass index, physical activity, smoking, Hopkins Symptom Checklist-25, comorbidities, and medications). The full samples included 4186 and 2031 individuals (HRV and BRS samples, respectively). Three subanalyses focused on individuals with intense and frequent pain, individuals with symptoms of depression and anxiety, and the relationship between pain intensity and autonomic parameters.

RESULTS

Linear regression models showed varying associations between NPS, pain intensity, and cardiovascular autonomic parameters. However, after all adjustments NPS was only associated with one outcome among women (BRS, standing: beta = - 0.015, p = 0.048) and two among men (HR, seated: beta = - 0.902, p = 0.003; HR, standing: beta = - 0.843, p = 0.014). Pain intensity was not associated with any outcome after full adjustments. Significant sex*pain interactions were found in the data.

CONCLUSIONS

Our data suggest that musculoskeletal pain has, at most, a limited independent association with cardiovascular autonomic function. Future studies should carefully account for the potential confounders and sex interactions that this study revealed.

Relationship Between Exercise-induced Oxidative Stress Changes and Parasympathetic Activity in Chronic Fatigue Syndrome: An Observational Study in Patients and Healthy Subjects

PURPOSE

Oxidative stress has been proposed as a contributor to pain in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). During incremental exercise in patients with ME/CFS, oxidative stress enhances sooner and antioxidant response is delayed. We explored whether oxidative stress is associated with pain symptoms or pain changes following exercise, and the possible relationships between oxidative stress and parasympathetic vagal nerve activity in patients with ME/CFS versus healthy, inactive controls.

METHODS

The present study reports secondary outcomes from a previous work. Data from 36 participants were studied (women with ME/CFS and healthy controls). Subjects performed a submaximal exercise test with continuous cardiorespiratory monitoring. Levels of thiobarbituric acid-reactive substances (TBARSs) were used as a measure of oxidative stress, and heart rate variability was used to assess vagal activity. Before and after the exercise, subjects were asked to rate their pain using a visual analogic scale.

FINDINGS

Significant between-group differences in pain at both baseline and following exercise were found (both, P < 0.007). In healthy controls, pain was significantly improved following exercise (P = 0.002). No change in oxidative stress level after exercise was found. Significant correlation between TBARS levels and pain was found at baseline (r = 0.540; P = 0.021) and after exercise (r = 0.524; P = 0.024) in patients only. No significant correlation between TBARS and heart rate variability at baseline or following exercise was found in either group. However, a significant correlation was found between exercise-induced changes in HRV and TBARS in healthy controls (r = -0.720; P = 0.001).

IMPLICATIONS

Oxidative stress showed an association with pain symptoms in people with ME/CFS, but no exercise-induced changes in oxidative stress were found. In addition, the change in parasympathetic activity following exercise partially accounted for the change in oxidative stress in healthy controls. More research is required to further explore this link.

Heart rate variability in adults with obstructive sleep apnea: a systematic review

Obstructive Sleep Apnea is a common respiratory disorder characterized by recurrent nocturnal episodes of normal breathing interruption due to upper airway total or partial collapse. Obstructive sleep apnea and cardiovascular diseases has similar risk factors, but the first is also a predisposing factor for cardiovascular pathologies independently of individuals demographic characteristics or risk markers. Heart rate variability is a non-invasive method to evaluate the regulation of autonomic nervous system and its a promising marker for health and disease, such as cardiovascular and respiratory diseases. The aim was to review whether heart rate variability is altered in patients with obstructive sleep apnea. We searched in five databases, including BIREME, Cochrane, Scholar Google, MEDLINE/PubMed and Periodics CAPES, and reference lists were also searched. Only cross-sectional studies comparing the heart rate variability of obstructive sleep patients with controls were included. Two authors independently extracted data and assessed trial quality. Twelve studies (513 participants with obstructive sleep apnea and 340 controls) met the inclusion criteria. This review evidence that adults with obstructive sleep apnea may demonstrate diminished vagal tone and higher sympathetic responsiveness.

The association between multisite musculoskeletal pain and cardiac autonomic modulation during work, leisure and sleep - a cross-sectional study

Background

The prevention and rehabilitation of multisite musculoskeletal pain would benefit from studies aiming to understand its underlying mechanism. Autonomic imbalance is a suggested mechanism for multisite pain, but hardly been studied during normal daily living. Therefore, the aim of the study is to investigate the association between multisite musculoskeletal pain and cardiac autonomic modulation during work, leisure and sleep.

Methods

This study is based on data from the “Danish Physical activity cohort with objective measurements” among 568 blue-collar workers. Pain intensity scales were dichotomized according to the median of each scale, and the number of pain sites was calculated. No site was regarded as the pain-free, one site was considered as single-site musculoskeletal pain and pain in two or more sites was regarded as multisite musculoskeletal pain. Heart rate variability (HRV) was measured by an electrocardiogram system (ActiHeart) and physical activity using accelerometers (Actigraph). Crude and adjusted linear mixed models were applied to investigate the association between groups and cardiac autonomic regulation during work, leisure and sleep.

Results

There was no significant difference between groups and no significant interaction between groups and domains in the crude or adjusted models for any HRV index. Significant differences between domains were found in the crude and adjusted model for all indices, except SDNN; sleep time showed higher values than leisure and work time, except for LF and LF/HF, which were higher during work.

Conclusion

This cross-sectional study showed that multisite musculoskeletal pain is not associated with imbalanced cardiac autonomic regulation during work, leisure and sleep time.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2312-3) contains supplementary material, which is available to authorized users.

The Immediate Effect of Therapeutic Touch and Deep Touch Pressure on Range of Motion, Interoceptive Accuracy and Heart Rate Variability: A Randomized Controlled Trial With Moderation Analysis

Background: There is paucity in the literature regarding the role of the interoceptive pathway through the insular cortex (IC), as well as heart rate variability (HRV) in relation to Osteopathic Manipulative Therapy (OMT) and deep-touch.

Aims: The present study investigated whether both OMT treatment and deep-touch (a newly hypothesized treatment option) was effective at altering the interoceptive pathway and HRV, whilst OMT was only expected to be effective for increasing Range of Motion (ROM).

Methods: Thirty-five healthy volunteers were randomly allocated into three conditions in a repeated measures crossover design; a control (laying supine on a plinth); deep-touch (head cradling); and an osteopathic mobilization therapeutic technique on the temporomandibular joint (TMJ). Interoceptive accuracy (IAc), HRV, as well as range of motion (ROM) for the TMJ area as well as the cervical spine (Csp) right and left measures were taken pre and post each condition setting.

Results: Significant condition effects emerged from the deep-touch and mobilization interventions for IAc where increases were identified through planned comparisons. For the HRV measure (RMSSD), a significant effect emerged in the deep-touch condition (increase) but not in the mobilization or control conditions. ROM did not increase for any condition. IAc correlated with post-ROM outcomes in many cases and HRV moderated some of these relations.

Conclusion: These results are discussed in the context of clinical practice, where cranial deep-touch maybe an effective treatment and modulator of the parasympathetic nervous systems, as well as the interoceptive system.

Heartbeat-enhanced immersive virtual reality to treat complex regional pain syndrome

Objectives

To develop and test a new immersive digital technology for complex regional pain syndrome (CRPS) that combines principles from mirror therapy and immersive virtual reality and the latest research from multisensory body processing.

Methods

In this crossover double-blind study, 24 patients with CRPS and 24 age- and sex-matched healthy controls were immersed in a virtual environment and shown a virtual depiction of their affected limb that was flashing in synchrony (or in asynchrony in the control condition) with their own online detected heartbeat (heartbeat-enhanced virtual reality [HEVR]). The primary outcome measures for pain reduction were subjective pain ratings, force strength, and heart rate variability (HRV).

Results

HEVR reduced pain ratings, improved motor limb function, and modulated a physiologic pain marker (HRV). These significant improvements were reliable and highly selective, absent in control HEVR conditions, not observed in healthy controls, and obtained without the application of tactile stimulation (or movement) of the painful limb, using a readily available biological signal (the heartbeat) that is most often not consciously perceived (thus preventing placebo effects).

Conclusions

Next to these specific and well-controlled analgesic effects, immersive HEVR allows the application of prolonged and repeated doses of digital therapy, enables the automatized integration with existing pain treatments, and avoids application of painful bodily cues while minimizing the active involvement of the patient and therapist.

Classification of evidence

This study provides Class III evidence that HEVR reduces pain and increases force strength in patients with CRPS.

The effects of propranolol on heart rate variability and quantitative, mechanistic, pain profiling: a randomized placebo-controlled crossover study

Background and aims

The autonomic nervous system (ANS) is capable of modulating pain. Aberrations in heart rate variability (HRV), reflective of ANS activity, are associated with experimental pain sensitivity, chronic pain, and more recently, pain modulatory mechanisms but the underlying mechanisms are still unclear. HRV is lowered during experimental pain as well as in chronic pain conditions and HRV can be increased by propranolol, which is a non-selective β-blocker. Sensitization of central pain pathways have been observed in several chronic pain conditions and human mechanistic pain biomarkers for these central pain pathways include temporal summation of pain (TSP) and conditioned pain modulation (CPM). The current study aimed to investigate the effect of the β-blocker propranolol, and subsequently assessing the response to standardized, quantitative, mechanistic pain biomarkers.

Methods

In this placebo-controlled, double-blinded, randomized crossover study, 25 healthy male volunteers (mean age 25.6 years) were randomized to receive 40 mg propranolol and 40 mg placebo. Heart rate, blood pressure, and HRV were assessed before and during experimental pain tests. Cuff pressure pain stimulation was used for assessment of pain detection (cPDTs) and pain tolerance (cPTTs) thresholds, TSP, and CPM. Offset analgesia (OA) was assessed using heat stimulation.

Results

Propranolol significantly reduced heart rate (p<0.001), blood pressure (p<0.02) and increased HRV (p<0.01) compared with placebo. No significant differences were found comparing cPDT (p>0.70), cPTT (p>0.93), TSP (p>0.70), OA-effect (p>0.87) or CPM (p>0.65) between propranolol and placebo.

Conclusions

The current study demonstrated that propranolol increased HRV, but did not affect pressure pain sensitivity or any pain facilitatory or modulatory outcomes.

Implications

Analgesic effects of propranolol have been reported in clinical pain populations and the results from the current study could indicate that increased HRV from propranolol is not associated with peripheral and central pain pathways in healthy male subjects.

Chronic Diffuse Pain and Functional Gastrointestinal Disorders After Traumatic Stress: Pathophysiology Through a Polyvagal Perspective

Chronic diffuse pain disorders, such as fibromyalgia, and functional gastrointestinal disorders (FGIDs), such as irritable bowel syndrome, place substantial burden on those affected and on the medical system. Despite their sizable impact, their pathophysiology is poorly understood. In contrast to an approach that focuses on the correlation between heart rate variability (HRV) and a specific organ or symptom, we propose that a bio-evolutionary threat-related autonomic response—as outlined in the Polyvagal Theory—may serve as a plausible explanation of how HRV, particularly respiratory sinus arrhythmia (RSA), would index the pathophysiology of these disorders. Evidence comes from: (1) the well-documented atypical autonomic regulation of the heart common to fibromyalgia and irritable bowel syndrome reflected in dampened RSA, (2) the neural architecture that integrates the heart, pain pathways, and the gastrointestinal tract, (3) the common physical co-morbidities shared by chronic diffuse pain and FGIDs, many of which are functionally regulated by the autonomic nervous system, (4) the elevated risk of chronic diffuse pain and FGIDs following traumatic stress or abuse, (5) and the elevated risk of chronic diffuse pain and FGIDs in individuals with anxiety and panic disorders. This novel conceptualization points to a pathogenesis rooted in changes to brain-body autonomic feedback loops in response to evolutionarily-salient threat cues, providing an integrated biopsychosocial model of chronic diffuse pain and FGIDs and suggesting new, non-pharmacological treatment strategies.

Interacting influences of gender and chronic pain status on parasympathetically mediated heart rate variability in adolescents and young adults

Considerable research links chronic pain to autonomic nervous system (ANS) dysfunction, specifically low heart rate variability (HRV) mediated by reduced parasympathetic activity. However, little is known about factors that influence ANS function in chronic pain. The ANS is the primary pathway for brain-gut communication, making it of particular interest in gastrointestinal disorders, such as irritable bowel syndrome, characterized by functional abdominal pain (FAP). We evaluated the relation of sex, pain severity, and psychological stress to ANS function in adolescents/young adults from a database of pediatric FAP and control participants enrolled 8 years earlier in a prospective study of pain. At follow-up in adolescence/young adulthood (Mean age = 19.46, SD = 3.48), we classified participants as Pain-Remit (n = 130), Pain-Persist (n = 96), and pain-free controls (n = 123). We recorded electrocardiogram data at rest and during laboratory stressors. Results demonstrated significantly lower HRV in Pain-Persist females compared with Pain-Remit females, female controls, and all males regardless of pain category. Spectral analysis of electrocardiogram showed that Pain-Persist females had reduced power in the high frequency domain of cardiac activity, ie, reduced parasympathetic "braking" of sympathetic activity, both at rest and during stress. Pain-Remit females exhibited levels of autonomic imbalance intermediate between those of females with persistent FAP and all other participants. Parasympathetically mediated low HRV in young women with persistent FAP may reflect a peripheral mechanism (eg, gut dysfunction) or a central nervous system mechanism (eg, pain amplification or poor emotion self-regulation) involving prolonged sympathetic activation.

Autonomic nerve activity indexed using 24-h heart rate variability in patients with burns

BACKGROUND

Heart rate variability (HRV) is a noninvasive method used to quantify fluctuations in the time interval between normal heart beats. The purpose of this study was to compare the autonomic nervous system functioning of patients with burns to healthy participants after their burn scars had been re-epithelialized.

MATERIALS AND METHODS

The authors prospectively performed 24-h HRV monitoring in 60 patients with electrical burns, those with other major burns, those with other minor burns, and 10 healthy participants. Analysis of HRV in the time and frequency domain was performed.

RESULTS

The difference in sympathetic nerve measures (standard deviation of NN intervals [SDNN], total power [TP] and a low frequency [LF] band) and parasympathetic nerve measures (Root mean square successive difference [RMSSD], the number of interval differences of successive NN intervals greater than 50ms [NN50], the percentage of differences between following RR intervals greater than 50ms [pNN50] and a high frequency [HF] band) in patients with burns was significantly decreased during the daytime and the nighttime. the difference in parasympathetic nerve measures were more significantly decreased during the nighttime compared with measures of HRV in healthy participants. The groups of other burns showed significantly lower HRV than the electrical burn group indexed by a very low frequency (VLF) measure and TP during the daytime.

CONCLUSION

We hypothesized that HRV is a surrogate for autonomic nervous system dysfunction in patients with burns. The patients with burns were observed a sympathetic predominance during daytime and a decreased parasympathetic activity during nighttime. These results of patients with other major burns were more predominant compared with the results of patients with other groups.

Intranasal oxytocin reduces heart rate variability during a mental arithmetic task: A randomised, double-blind, placebo-controlled cross-over study

Heart rate variability (HRV) refers to variation in the interval between successive heart beats. Low HRV is an indicator of potential autonomic nervous system dysfunction. People with chronic pain often display autonomic dysregulation, especially in the parasympathetic nervous system. The hormone oxytocin has been shown to increase HRV in non-clinical samples, but its potential impact on HRV in persons with chronic pain is unknown. This study investigated the impact of intranasal oxytocin on HRV in persons with chronic neck and shoulder pain. Participants included 24 individuals with chronic neck and shoulder pain lasting >12months and 24 age- and sex-matched pain-free controls. In a randomised double-blind, placebo-controlled, cross-over study, participants self-administered intranasal oxytocin (24IU) in one session, and placebo in another, before HRV was recorded at rest and during a mental arithmetic task. Intranasal oxytocin did not influence HRV at rest. However, compared to placebo, intranasal oxytocin elicited small decreases in low-frequency and high-frequency HRV in both groups during the mental arithmetic task. These results suggest that intranasal oxytocin may enhance the salience of the mental arithmetic task, leading to reduced engagement of the parasympathetic nervous system when completing the task. Further investigation and replication of these findings are required to improve our understanding of the effects of intranasal oxytocin on autonomic functioning both at rest and under cognitive stress.

The effects of slow-paced versus mechanically assisted breathing on autonomic function in fibromyalgia patients

Paced breathing has shown efficacy in fibromyalgia (FM), but the mechanisms associated with symptom change are largely unknown. We investigated whether changes in respiratory rate (RR) alone resulted in autonomic changes during normal, paced, and mechanically assisted breathing in untrained FM patients and controls. Participants included 20 FM patients and 14 controls matched for age and body mass index. During a single visit, participants completed three 15-minute breathing sessions: 1) normal breathing, 2) slow-paced breathing, and 3) mechanically assisted breathing (continuous positive airway pressure) while supine. Continuous blood pressure and electrocardiogram were recorded, and measures of heart rate variability (HRV) and spontaneous baroreceptor sensitivity (sBRS) were calculated. During normal breathing, FM patients had higher heart rate (HR), but lower HRV and sBRS variables compared to controls with no difference in RR. Compared to the paced breathing condition, FM patients had significantly lower HR with higher HRV and sBRS variables during mechanically assisted breathing, despite no significant change in RR. Mechanically assisted breathing provided greater benefits in autonomic function than paced breathing in untrained FM patients. Future research will be needed to elucidate the central pathways involved in these autonomic changes and whether training in paced breathing can eventually replicate the results seen in mechanically assisted patients.

Evidence of reduced parasympathetic autonomic regulation in inflammatory joint disease: A meta-analyses study

BACKGROUND

Rheumatoid arthritis (RA) and spondyloarthritis (SpA) are inflammatory joint disorders (IJD) with increased risk of cardiovascular disease (CVD). Autonomic dysfunction (AD) is a risk factor for CVD, and parasympathetic AD is linked to key features of IJD such as inflammation, physical inactivity and pain. Heart-rate variability (HRV) is a marker of cardiac AD. The study objective was to compare parasympathetic cardiac AD, measured by HRV, between patients with IJD and healthy controls, using meta-analysis methodology, and to examine the impact of inflammation, physical inactivity and pain on HRV in IJD.

METHODS

Medline, Embase and Amed were searched. Inclusion criteria were adult case-control studies published in English or a Scandinavian language, presenting HRV data in IJD. Two measures of HRV and 3 from the Ewing protocol were selected: square root of mean squared difference of successive R-R intervals (RMSSD), high frequency (HF), Ewing protocol; standing (E-S), breathing (E-B) and Valsalva (E-V). Patients with RA, SpA and healthy controls were compared separately using random-effects meta-analyses of standardized mean differences (SMD).

RESULTS

In all, 35 papers were eligible for inclusion. For RMSSD the pooled SMD (95% CI) RA vs. controls was -0.90 (-1.35 to -0.44), for SpA vs. controls; -0.34 (-0.73 to 0.06). For HF pooled SMD RA vs. controls was -0.78 (-0.99 to -0.57), for SpA vs. controls; -0.04 (-0.22 to 0.13). All Ewing parameters were significantly lower in cases, except for E-V which was comparable between cases and controls in patients with RA.

CONCLUSION

Patients with IJD have cardiac parasympathetic AD which is related to inflammation.

Identifying characteristics of the most severely impaired chronic pain patients treated at a specialized inpatient pain clinic

BACKGROUND AND AIMS

Patients suffering from chronic nonmalignant pain constitute a heterogeneous population in terms of clinical presentation and treatment results. Few data are available about what distinguishes different groups in this huge population of patients with chronic persistent pain (CPP). A subgroup that is poorly studied, consists of the most severely impaired chronic pain patients. At the Uppsala University Hospital Pain Clinic, there is a specialized department accepting the most complex patients for rehabilitation. In the endeavour to improve and evaluate treatment for this subgroup, a better understanding of the complex nature of the illness is essential. This prospective study aimed to describe the characteristics of this subgroup of patients with CPP.

METHODS

Seventy-two consecutive patients enrolled in the Uppsala programme were evaluated. We collected data on demographics, type of pain and experienced symptoms other than pain using a checklist of 41 possible symptoms. Psychiatric comorbidity was assessed by a psychiatrist using a structured clinical interview. Quality of life (QoL), pain rating and medication/drug/alcohol usage were measured by validated questionnaires: SF-36, NRS, DUDIT and AUDIT. Concerning physical functioning and sick leave, a comparison was made with data from the Swedish Quality Register Registry for pain rehabilitation (SQRP).

RESULTS

The cohort consisted of 61% women and the average age was 45 (range 20-70) years. For this cohort, 74% reported being on sick leave or disability-pension. In the SQRP 59% were on sick leave at the time they entered the rehabilitation programmes [1]. On average, the study-population reported 22 symptoms other than pain, to be at a high rate of severity. Patients treated in conventional pain-rehabilitation programmes reported a mean of 10 symptoms in average. Symptoms reported with the highest frequency (>80%), were lethargy, tiredness, headache and difficulties concentrating. Seventy-six percent were diagnosed with a psychiatric disorder. Sixty-nine fulfilled the criteria for depression or depression/anxiety disorder despite that most (65%) were treated with psychotropic medication. Alcohol/drug abuse was minimal. Seventy-one percent were on opioids but the doses were moderate (<100mg) MEq. The pain rating was ≥7 (out of a maximum of 10) for 60% of the patients.

CONCLUSION

This study describes what makes the subgroup of pain patients most affected by their pain special according to associated factors and comorbidity We found that they were distinguished by a high degree of psychiatric comorbidity, low physical functioning and extreme levels of symptom preoccupation/hypervigilance. Many severe symptoms additional to pain (e.g. depression/anxiety, tiredness, disturbed sleep, lack of concentration, constipation) were reported. The group seems hypervigilant, overwhelmed with a multitude of different symptoms on a high severity level.

IMPLICATIONS

When treating this complex group, the expressions of the illness can act as obstacles to achieve successful treatment outcomes. The study provides evidence based information, for a better understanding of the needs concerning these pain patients. Our result indicates that parallel assessment and treatment of psychiatric comorbidities and sleep disorders combined with traditional rehabilitation, i.e. physical activation and cognitive reorganization are imperative for improved outcomes.

Cardiovascular autonomic regulation, inflammation and pain in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic inflammatory condition characterised by reduced heart rate variability (HRV) of unknown cause. We tested the hypothesis that low HRV, indicative of cardiac autonomic cardiovascular dysfunction, was associated with systemic inflammation and pain. Given the high prevalence of hypertension (HTN) in RA, a condition itself associated with low HRV, we also assessed whether the presence of hypertension further reduced HRV in RA.

Methods

In RA-normotensive (n = 13), RA-HTN (n = 17), normotensive controls (NC; n = 17) and HTN (n = 16) controls, blood pressure and heart rate were recorded. Time and frequency domain measures of HRV along with serological markers of inflammation (high sensitivity C-reactive protein [hs-CRP], tumour necrosis factor-α [TNF-α] and interleukins [IL]) were determined. Reported pain was assessed using a visual analogue scale.

Results

Time (rMSSD, pNN50%) and frequency (high frequency power, low frequency power, total power) domain measures of HRV were lower in the RA, RA-HTN and HTN groups, compared to NC (p = 0.001). However, no significant differences in HRV were noted between the RA, RA-HTN and HTN groups. Inverse associations were found between time and frequency measures of HRV and inflammatory cytokines (IL-6 and IL-10), but were not independent after multivariable analysis. hs-CRP and pain were independently and inversely associated with time domain (rMMSD, pNN50%) parameters of HRV.

Conclusions

These findings suggest that lower HRV is associated with increased inflammation and independently associated with increased reported pain, but not compounded by the presence of HTN in patients with RA.

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Rheumatoid arthritis (RA) is a chronic inflammatory condition accompanied by low heart rate variability (HRV).

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Important autonomic-immune interactions are suggested, but have not been thoroughly examined in RA.

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We show that low HRV in RA is associated with increased serum inflammatory cytokine levels and patient-reported pain.

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In our patients with RA, reductions in HRV were not compounded by the presence of hypertension.

Reiki Is Better Than Placebo and Has Broad Potential as a Complementary Health Therapy

This study reviews the available clinical studies of Reiki to determine whether there is evidence for Reiki providing more than just a placebo effect. The available English-language literature of Reiki was reviewed, specifically for peer-reviewed clinical studies with more than 20 participants in the Reiki treatment arm, controlling for a placebo effect. Of the 13 suitable studies, 8 demonstrated Reiki being more effective than placebo, 4 found no difference but had questionable statistical resolving power, and only one provided clear evidence for not providing benefit. Viewed collectively, these studies provide reasonably strong support for Reiki being more effective than placebo. From the information currently available, Reiki is a safe and gentle "complementary" therapy that activates the parasympathetic nervous system to heal body and mind. It has potential for broader use in management of chronic health conditions, and possibly in postoperative recovery. Research is needed to optimize the delivery of Reiki.

The efficacy of a preparatory phase of a touch-based approach in treating chronic low back pain: a randomized controlled trial

Background

Massage therapy is an important element of rehabilitation in the treatment of chronic low back pain (CLBP). The objective of this study was to determine the relative efficacy of massage therapy between traditional massage and a new massage approach for CLBP. We also examined whether any reduction in pain was linked to interoceptive awareness and parasympathetic activation.

Methods

A single-blind, randomized, controlled trial of 51 patients who were allocated into a traditional massage therapy group (TMG; N=24, mean age: 50.54±9.13 years) or experimental massage therapy group (SMG; N=27, mean age: 50.77±6.80 years). The primary outcome was the reduction in pain per the visual analog scale (VAS); the secondary outcome measures were multidimensional pain intensity on the McGill Pain Questionnaire, pain-related disability per the Waddel Disability Index, interoceptive awareness per the Multidimensional Assessment of Interoceptive Awareness Questionnaire, quality of life per the Short Form - 12 Health Survey, and heart rate variability, expressed as the coherence ratio (CR) by photoplethysmography. The following outcome measures were assessed at baseline, at the end of the treatment program, and at the 3-month follow-up. The mean and standard deviation were calculated for continuous data. Mann–Whitney U test was used to perform between-group comparisons, Friedman’s analysis was used for data on the 3 assessment times in each group, and Spearman’s R coefficient was used to analyze correlations.

Results

Both approaches had a positive result on pain, an effect that was more acute in the SMG versus TMG for all pain scales, with better maintenance at the 3-month follow-up (VAS p=0.005 and p=0.098; Waddell Index p=0.034 and 0.044; McGill total p=0.000 and 0.003). In the SMG, CR scores were significant at baseline and at the end of the treatment program (p=0.000 and 0.002).

Conclusion

The new massage approach with a preparatory phase that is pleasant to the touch was more effective than the traditional approach for CLBP.

Increasing Performance of Professional Soccer Players and Elite Track and Field Athletes with Peak Performance Training and Biofeedback: A Pilot Study

The aim of this pilot study was to investigate the effects of an intervention consisting of mental coaching combined with either electro encephalogram (EEG) alpha power feedback or heart rate variability (HRV) feedback on HRV, EEG outcomes and self-reported factors related to stress, performance, recovery and sleep quality in elite athletes. A prospective pilot study was performed with two distinct cohorts. Soccer players were provided with four sessions of mental coaching combined with daily HRV biofeedback (Group A); track and field athletes were provided with four sessions of mental coaching in combination with daily neurofeedback (Group B). Measurements were performed at baseline, post intervention and at 5 weeks follow-up. Objective measures: EEG and ECG. Subjective measures: Numeric Rating Scale for performance, Pittsburgh Sleep Quality Index, Rest and Stress Questionnaire and Sports Improvement-60. Group characteristics were too distinct to compare the interventions. Linear mixed models were used to analyze differences within groups over time. In Group A, significant changes over time were present in alpha power at 5 of 7 EEG locations (p < 0.01–0.03). LF/HF ratio significantly increased (p = 0.02) and the concentration (p = 0.02) and emotional scale (p = 0.03) of the SIM-60 increased significantly (p = 0.04). In Group B, the HRV low frequency power and recovery scale of the REST-Q significantly increased (p = 0.02 and <0.01 resp.). Other measures remained stable or improved non-significantly. A mental coaching program combined with either HRV or EEG alpha power feedback may increase HRV and alpha power and may lead to better performance-related outcomes and stress reduction. Further research is needed to elucidate the effects of either type of feedback and to compare effects with a control group.

Statistical considerations for reporting and planning heart rate variability case-control studies

The calculation of heart rate variability (HRV) is a popular tool used to investigate differences in cardiac autonomic control between population samples. When interpreting effect sizes to quantify the magnitude of group differences, researchers typically use Cohen's guidelines of small (0.2), medium (0.5), and large (0.8) effects. However, these guidelines were originally proposed as a fallback for when the effect size distribution (ESD) was unknown. Despite the availability of effect sizes from hundreds of HRV studies, researchers still largely rely on Cohen's guidelines to interpret effect sizes and to perform power analyses to calculate required sample sizes for future research. This article describes an ESD analysis of 297 HRV effect sizes from between-group/case-control studies, revealing that the 25th, 50th, and 75th effect size percentiles correspond with effect sizes of 0.26, 0.51, and 0.88, respectively. The analyses suggest that Cohen's guidelines may underestimate the magnitude of small and large effect sizes and that HRV studies are generally underpowered. Therefore, to better reflect the observed ESD, effect sizes of 0.25, 0.5, and 0.9 should be interpreted as small, medium, and large effects (after rounding to the closest 0.05). Based on power calculations using the ESD, suggested sample sizes are also provided for planning suitably powered studies that are more likely to replicate. Researchers are encouraged to use the ESD data set or their own collected data sets in tandem with the provided analysis script to perform custom ESD and power analyses relevant to their specific research area.

Effects of closure versus non-closure of the visceral and parietal peritoneum at cesarean section: does it have any effect on postoperative vital signs? A prospective randomized study

OBJECTIVE

To investigate the effect of peritonization at cesarean section on postoperative vital signs which was thought to be an indirect finding secondary to increased sympathetic activity originated from pain caused by stretched peritoneum.

METHODS

One hundred and thirty-three pregnant women were randomized to four groups; Closure of parietal peritoneum only (group 1; n = 32), closure of visceral and parietal peritoneums (group 2; n = 32), no closure of peritoneums (group 3; n = 32) and closure of the visceral peritoneum only (group 4; n = 32). All participants were monitored for blood pressure, pulse activity and hourly urinary output during the first postoperative 24 h. Postoperative pain was measured using a Visual Analogue Scale 6th and 24th hours after surgery. Return of bowel function was measured from the end of the operation to the first passage of flatus. Operating time, pre- and postoperative hemoglobin, postoperative complications, length of hospital stay and postoperative urine osmolarity were noted.

RESULTS

The mean surgery duration was significantly longer in group 2. Diuresis was found significantly decreased in group 2. Pulse rate and systolic and diastolic blood pressure were significantly higher in group 2. Closure of both peritoneums was associated with higher post-operative pain as assessed using Visual analogue scale score analyses in group 2.

CONCLUSION

Both visceral and parietal membrane closure in cesarean section should be avoided in women with hypertensive disorders, renal function abnormalities and autonomic dysfunction because of increased postoperative pain and associated sympathetic overactivity.

Dysfunctional stress responses in chronic pain

Many dysfunctional and chronic pain conditions overlap. This review describes the different modes of chronic deregulation of the adaptive response to stress which may be a common factor for these conditions. Several types of dysfunction can be identified within the hypothalamo-pituitary-adrenal axis: basal hypercortisolism, hyper-reactivity, basal hypocortisolism and hypo-reactivity. Neuroactive steroid synthesis is another component of the adaptive response to stress. Dehydroepiandrosterone (DHEA) and its sulfated form DHEA-S, and progesterone and its derivatives are synthetized in cutaneous, nervous, and adipose cells. They are neuroactive factors that act locally. They may have a role in the localization of the symptoms and their levels can vary both in the central nervous system and in the periphery. Persistent changes in neuroactive steroid levels or precursors can induce localized neurodegeneration. The autonomic nervous system is another component of the stress response. Its dysfunction in chronic stress responses can be expressed by decreased basal parasympathethic activity, increased basal sympathetic activity or sympathetic hyporeactivity to a stressful stimulus. The immune and genetic systems also participate. The helper-T cells Th1 secrete pro-inflammatory cytokines such as IL-1-β, IL-2, IL-6, IL-8, IL-12, IFN-γ, and TNF-α, whereas Th2 secrete anti-inflammatory cytokines: IL-4, IL-10, IGF-10, IL-13. Chronic deregulation of the Th1/Th2 balance can occur in favor of anti- or pro-inflammatory direction, locally or systemically. Individual vulnerability to stress can be due to environmental factors but can also be genetically influenced. Genetic polymorphisms and epigenetics are the main keys to understanding the influence of genetics on the response of individuals to constraints.

Psychoneuroimmunological aspects of cardiovascular diseases: a preliminary report

Aim of the study

Due to their prevalence and negative social effects, cardiovascular diseases belong to a group of civilization diseases. Previous research suggests comorbidity of heart diseases, mood disorders and impaired cognitive functioning. The aim of this study was to evaluate the psychoneuroimmunological aspects of functioning in patients diagnosed with cardiovascular diseases.

Material and methods

Ten persons, mean age 48.2 years old, diagnosed with primary hypertension, were studied. All of them were treated with beta blockers and ACE inhibitors with unsuccessful therapeutic effect. This group also included 4 subjects with heart rate disturbances. The control group included 10 clinically healthy volunteers in mean age 46.8. All participants had 24-hour ECG monitoring with Holter method in order to evaluate the autonomic activity with time and frequency domain analysis (heart rate variability). Patients also underwent neuropsychological assessment of quality of life and personality traits (EQ-5D, NEO-PI-R, PSS10, SWLS, MHLC). Quantitative evaluation of immune system parameters included: TCD3, TCD4, CD8, CD16/CD56, CD19, HLA-DR+.

Results

The cardiovascular disease group showed significantly lower time and frequency domain parameters (p < 0.05) except low/high frequency (LF/HF) power ratio. The heart rhythm disorder group demonstrated significant relationships such as: Quality of life with Total Power of HRV and day-time LF/HF ratio, pNN50 and rMSSD – negative correlation.

Conclusions

1. In cardiovascular disease patients, activity of the autonomic nervous system is significantly reduced. 2. Impaired modulation of the autonomic nervous system activity affects mood and decreases quality of life. 3. In patients with heart rhythm disturbances, increased sympathetic nervous system activity affects prolonged tension and the immune response.

Heart rate variability in chronic low back pain patients randomized to yoga or standard care

Background

Chronic pain can alter the autonomic balance with increased sympathetic activity reflected in altered heart rate variability (HRV). It has been proposed that yoga can be useful to correct the autonomic imbalance in patients with chronic pain who have reduced HRV.

Methods and designs

In the present randomized controlled trial 62 patients with chronic low back pain associated with altered alignment of intervertebral discs (aged between 20 and 45 years, 32 males) were randomized to 2 groups. One group received yoga for 3 months while the other group carried out standard medical care based on the physician's advice. The duration was the same, i.e., 3 months. The heart rate variability and rate of respiration were assessed at baseline and at the end of 3 months.

Results

There was a significant difference in the baseline (pre) values between groups (p = 0.008) for respiration rate which was higher in the yoga group. The changes reported below are pre-post comparisons within each group. The yoga group showed a significant (p < 0.05; repeated measures ANOVA, post-hoc analyses) decrease in the LF power of HRV, rate of respiration and a significant increase in the HF power of HRV and in the pNN50.

Conclusion

The results suggest that yoga practice can shift the autonomic balance towards vagal dominance in patients with chronic low back pain associated with altered alignment of intervertebral discs.

Trial registration

The study is registered with the Clinical Trials Registry of India (CTRI/2012/11/003094) and can be accessed at.