Heart rate variability as a biomarker for autonomic nervous system response differences between children with chronic pain and healthy control children

Heart Rate Variability Applications in Medical Specialties: A Narrative Review

HRV is clinically considered to be a surrogate measure of the asymmetrical interplay of the sympathetic and parasympathetic nervous system. While HRV has become an increasingly measured variable through commercially-available wearable devices, HRV is not routinely monitored or utilized in healthcare settings at this time. The purpose of this narrative review is to discuss and evaluate the current research and potential future applications of HRV in several medical specialties, including critical care, cardiology, pulmonology, nephrology, gastroenterology, endocrinology, infectious disease, hematology and oncology, neurology and rehabilitation, sports medicine, surgery and anesthesiology, rheumatology and chronic pain, obstetrics and gynecology, pediatrics, and psychiatry/psychology. A narrative literature review was conducted with search terms including HRV and relevant terminology to the medical specialty in question. While HRV has demonstrated promise for some diagnoses as a non-invasive, easy to use, and cost-effective metric for early disease detection, prognosis and mortality prediction, disease monitoring, and biofeedback therapy, several issues plague the current literature. Substantial heterogeneity exists in the current HRV literature which limits its applicability in clinical practice. However, applications of HRV in psychiatry, critical care, and in specific chronic diseases demonstrate sufficient evidence to warrant clinical application regardless of the surmountable research issues. More data is needed to understand the exact impact of standardizing HRV monitoring and treatment protocols on patient outcomes in each of the clinical contexts discussed in this paper.

The Combined Effects of Cold Foot Bath and Lavender Oil Inhalation on Autonomic Variables in Healthy Volunteers: A Randomized Controlled Trial

BACKGROUND AND AIM

An essential function of the autonomic nerve system is to regulate physiological processes and stress responses in the body. Cold foot baths and aromatherapy with lavender oil each influence autonomic functions, but their combined effect in healthy individuals is unknown. The purpose of this study is to look into how autonomic variability in healthy volunteers is affected by both inhaling lavender oil and taking cold foot baths.

METHODS

A total of 60 healthy individuals were randomized to be placed in either the control group (n=30) or the experimental group (n=30) and were instructed to attend a single designated session. The control group underwent a 20-minute cold foot bath, while the experimental group received a 20-minute cold foot bath combined with lavender oil inhalation. Assessments were carried out before, during, and after the interventions.

OUTCOME MEASURES

To evaluate autonomic variables, we monitored galvanic skin response (GSR) and Heart Rate Variability (HRV) using an equivital belt. Furthermore, we measured blood pressure (BP) and mean arterial pressure (MAP) before, during (20 minutes) the intervention, and after a 10-minute resting period; post-intervention measurements were taken.

RESULTS

Repeated measures analysis revealed a significant difference in standard deviation of normal-to-normal intervals (SDNN), pNN50, and heart rate (HR) for time-domain variables (p<0.05), whereas the frequency-domain analysis showed a significant difference over time in LF/HF, LF, and HF (p<0.05). When these were compared between the groups, a significant difference was observed only in LF and HF (p<0.04). Additionally, a statistically significant difference (p<0.001) in diastolic and systolic blood pressure between the groups was noted.

CONCLUSION

The combination of a cold foot bath and lavender oil inhalation may modulate autonomic activity, promoting relaxation by vagal balance in healthy individuals.

Physiological response to pain in patients with temporomandibular joint disorders during physiotherapy

Pain assessment in patients with temporomandibular joint (TMJ) disorders during physiotherapy is a challenging yet desired task. Our study addresses two issues. First, we compare the pain perception in patients with TMJ disorders and a control group. The hand dynamometer is verified as an alternate pain self-report device in the second stage. For the dynamometer validation, we employed a cuff-pressure test to induce pain of various intensities. In the second stage, physiological signals (electrodermal activity and blood volume pulse) have been acquired during the physiotherapy in a control group and patients suffering from TMJ disorder. The linear mixed-effects modeling is carried out to find differences in pain and no pain states, considering subjects' health condition. The main result of the present pilot study is that physiological reactions to painful physiotherapy do not differ between patients with chronic pain and the control group. This finding concludes that studies on TMJ disorder procedures may also be performed on healthy subjects.

Surgical treatment of refractory low back pain using implanted BurstDR spinal cord stimulation (SCS) in a cohort of patients without options for corrective surgery: Findings and results from the DISTINCT study, a prospective randomized multi-center-controlled trial

Background

Low back pain (LBP) is a highly prevalent, disabling condition affecting millions of people. Patients with an identifiable anatomic pain generator and resulting neuropathic lower extremity symptoms often undergo spine surgery, but many patients lack identifiable and/or surgically corrective pathology. Nonoperative treatment options often fail to provide sustained relief. Spinal cord stimulation (SCS) is sometimes used to treat these patients, but the lack of level 1 evidence limits its widespread use and insurance coverage. The DISTINCT RCT study evaluates the efficacy of passive recharge burst SCS compared to conventional medical treatment (CMM) in alleviating chronic, refractory axial low back pain.

Methods

This prospective, multicenter, randomized, study with an optional 6-month crossover involved patients who were not candidates for lumbar spine surgery. The primary and secondary endpoints evaluated improvements in low back pain intensity (NRS), back pain-related disability (ODI), pain catastrophizing (PCS), and healthcare utilization. Patients were randomized to SCS therapy or CMM at 30 US study sites.

Results

The SCS arm reported an 85.3% NRS responder rate (≥ 50% reduction) compared to 6.2% (5/81) in the CMM arm. After the 6M primary endpoint, SCS patients elected to remain on assigned therapy and 66.2% (49/74) of CMM patients chose to trial SCS (crossover). At the 12M follow-up, SCS and crossover patients reported 78.6% and 71.4% NRS responder rates. Secondary outcomes indicated significant improvements in ODI, PCS, and reduced healthcare utilization. Six serious adverse events were reported and resolved without sequelae.

Conclusion

DISTINCT chronic low back pain patients with no indication for corrective surgery experienced a significant and sustained response to burst SCS therapy for up to 12 months. CMM patients who crossed over to the SCS arm reported profound improvements after 6 months. This data advocates for a timely consideration of SCS therapy in patients unresponsive to conservative therapy.

Link between Yoga and Heart Rate Variability: Can Yoga Enhance the Cardiac Resonance

Cardiac resonance is a complicated phenomenon involving the coordinated oscillations of numerous circulatory system components, such as electrical activity, contraction and relaxation, and blood flow. It is critical for the normal functioning of the heart and for maintaining blood flow throughout the body. Cardiac resonance is defined as a series of tiny waves produced by the heartbeat and overlaid on flow data and airway pressures. A variety of technologies, including cardiac magnetic resonance (CMR) imaging, can be used to identify these waves. CMR is a strong noninvasive method for seeing and quantifying heart anatomy and function in great detail. CMR can be used to assess cardiac resonance in both healthy and heart disease patients. A regular and coordinated pattern of oscillations characterizes cardiac resonance in healthy persons. In patients with heart illness, however, cardiac resonance can be interrupted, resulting in diminished cardiac function and decreased blood flow. The intricate role of cardiac resonance in cardiac health and disease is continuously being studied by researchers. However, it is obvious that cardiac resonance is an exciting area of research that has the potential to change the way to identify and treat heart illness. Yoga is a mind-body practice that has been demonstrated to have numerous cardiovascular health advantages, such as improved heart function, reduced inflammation, and lower blood pressure. Yoga is hypothesized to promote cardiac resonance by encouraging coordinated oscillations of numerous cardiovascular system components. Various researches have shown buoyant results such as yoga can be helpful in improving heart rate variability, cardiac resonance and reducing arterial stiffness. Stress can disrupt cardiac resonance and increase the risk of heart disease. More research is needed to completely understand the mechanisms that impact cardiac resonance and the long-term advantages of yoga for heart health.

Exploring a multimodal approach for utilizing digital biomarkers for childhood mental health screening

Background

Depression and anxiety are prevalent mental health concerns among children and adolescents. The application of conventional assessment methods, such as survey questionnaires to children, may lead to self-reporting issues. Digital biomarkers provide extensive data, reducing bias in mental health self-reporting, and significantly influence patient screening. Our primary objectives were to accurately assess children's mental health and to investigate the feasibility of using various digital biomarkers.

Methods

This study included a total of 54 boys and girls aged between 7 to 11 years. Each participant's mental state was assessed using the Depression, Anxiety, and Stress Scale. Subsequently, the subjects participated in digital biomarker collection tasks. Heart rate variability (HRV) data were collected using a camera sensor. Eye-tracking data were collected through tasks displaying emotion-face stimuli. Voice data were obtained by recording the participants' voices while they engaged in free speech and description tasks.

Results

Depressive symptoms were positively correlated with low frequency (LF, 0.04-0.15 Hz of HRV) in HRV and negatively associated with eye-tracking variables. Anxiety symptoms had a negative correlation with high frequency (HF, 0.15-0.40 Hz of HRV) in HRV and a positive association with LF/HF. Regarding stress, eye-tracking variables indicated a positive correlation, while pNN50, which represents the proportion of NN50 (the number of pairs of successive R-R intervals differing by more than 50 milliseconds) divided by the total number of NN (R-R) intervals, exhibited a negative association. Variables identified for childhood depression included LF and the total time spent looking at a sad face. Those variables recognized for anxiety were LF/HF, heart rate (HR), and pNN50. For childhood stress, HF, LF, and Jitter showed different correlation patterns between the two grade groups.

Discussion

We examined the potential of multimodal biomarkers in children, identifying features linked to childhood depression, particularly LF and the Sad.TF:time. Anxiety was most effectively explained by HRV features. To explore reasons for non-replication of previous studies, we categorized participants by elementary school grades into lower grades (1st, 2nd, 3rd) and upper grades (4th, 5th, 6th).

Conclusion

This study confirmed the potential use of multimodal digital biomarkers for children's mental health screening, serving as foundational research.

The efficacy of manual therapy on HRV in those with long-standing neck pain: a systematic review

OBJECTIVES

Long-standing neck pain (LNP) is a clinical condition frequently encountered in the physical therapy clinic. LNP is a complex, multifactorial condition affecting multiple body systems including the autonomic nervous system (ANS). Traditionally, research on the impact of physical therapy on LNP has focused on self-report measures and pain scales. Heart rate variability (HRV) is an objective measure of the ANS, allowing for quantification of effects of treatment. This systematic review is intended to evaluate if manual therapy acutely affects heart rate variability in adults with long-standing neck pain.

METHODS

Pubmed, Medline, CINAHL, Google Scholar, Web of Science, and Cochrane library were used to retrieve the randomized controlled trials for this review between the years 2010-2021. Search terms included: chronic neck pain, neck pain, cervical pain, manual therapy, mobilization, manipulation, osteopathy, osteopathic or chiropractic. Heart rate variability, HRV, heart rate variation, effects, outcomes, benefits, impacts or effectiveness.

RESULTS

Of 139 articles located and screened, three full-text articles were selected for full qualitative synthesis, with a combined population of 112 subjects, 91 of which were female, with an average age of 33.7 ± 6.8 years for all subjects. MT techniques in three studies were statistically significant in improving HRV in people with LNP; however, techniques were differed across studies, while one study showed no benefit. The studies were found to be of high quality with PEDro scores ≥6.

CONCLUSIONS

Although no clear cause and effect relationship can be established between improvement in HRV with manual therapy, results supported the use of MT for an acute reduction in HRV. No one particular method of MT has proven superior, MT has been found to produce a statistically significant change in HRV. These HRV changes are consistent with decreased sympathetic tone and subjective pain.

Effects of COVID-19 on the Autonomic Cardiovascular System: Heart Rate Variability and Turbulence in Recovered Patients

BACKGROUND

COVID-19 may be a risk factor for developing cardiovascular autonomic dysfunction. Data are limited, however, on the association between heart rate variability, heart rate turbulence, and COVID-19. The aims of this study were to evaluate the effect of COVID-19 on the cardiovascular autonomic system in patients with persistent symptoms after recovering from COVID-19 and to determine whether these patients showed changes in ambulatory electrocardiography monitoring.

METHODS

Fifty-one adults who had confirmed SARS-CoV-2 infection and presented with persistent symptoms to the cardiology outpatient clinic after clinical recovery between April and June 2021 were included. Patients were prospectively followed for 6 months. The patients were evaluated at the time of first application to the cardiology outpatient clinic and at 6 months after presentation. Ambulatory electrocardiography monitoring and echocardiographic findings were compared with a control group of 95 patients.

RESULTS

Patients in the post-COVID-19 group had significantly higher mean (SD) turbulence onset (0.39% [1.82%] vs -1.37% [2.93%]; P < .001) and lower heart rate variability than those in the control group at both initial and 6-month evaluations. The post-COVID-19 group had no significant differences in echocardiographic findings compared with the control group at 6 months, except for right ventricle late diastolic mitral annular velocity (P = .034). Furthermore, turbulence onset was significantly correlated with turbulence slope (r = -0.232; P = .004), heart rate variability, and the parameters of left (r = -0.194; P=.049) and right (r = 0.225; P = .02) ventricular diastolic function.

CONCLUSIONS

COVID-19 may cause cardiovascular autonomic dysfunction. Heart rate variability and turbulence parameters can be used to recognize cardiovascular autonomic dysfunction in patients who have recovered from COVID-19 but have persistent symptoms.

Objective wearable measures correlate with self-reported chronic pain levels in people with spinal cord stimulation systems

Spinal Cord Stimulation (SCS) is a well-established therapy for treating chronic pain. However, perceived treatment response to SCS therapy may vary among people with chronic pain due to diverse needs and backgrounds. Patient Reported Outcomes (PROs) from standard survey questions do not provide the full picture of what has happened to a patient since their last visit, and digital PROs require patients to visit an app or otherwise regularly engage with software. This study aims to assess the feasibility of using digital biomarkers collected from wearables during SCS treatment to predict pain and PRO outcomes. Twenty participants with chronic pain were recruited and implanted with SCS. During the six months of the study, activity and physiological metrics were collected and data from 15 participants was used to develop a machine learning pipeline to objectively predict pain levels and categories of PRO measures. The model reached an accuracy of 0.768 ± 0.012 in predicting the pain intensity of mild, moderate, and severe. Feature importance analysis showed that digital biomarkers from the smartwatch such as heart rate, heart rate variability, step count, and stand time can contribute to modeling different aspects of pain. The results of the study suggest that wearable biomarkers can be used to predict therapy outcomes in people with chronic pain, enabling continuous, real-time monitoring of patients during the use of implanted therapies.

Group Changes in Cortisol and Heart Rate Variability of Children with Down Syndrome and Children with Autism Spectrum Disorder during Dog-Assisted Therapy

Dog-assisted therapy is hypothesized to lower stress in children with autism spectrum disorder (ASD) and children with Down syndrome (DS), which may be visible on a physiological level. In this study, we measured heart rate variability (HRV) and salivary cortisol of 20 children with DS or ASD at the beginning and end of six weekly sessions of dog-assisted therapy. We found a decrease of cortisol levels during single sessions, but no overall effect after six sessions (six weeks). The effect of dog-assisted therapy on the increase of HRV could not be confirmed. This study is one of the first to use physiological measurements to test the effects of DAT.

Interactive Cardio System for Healthcare Improvement

The paper presents an interactive cardio system that can be used to improve healthcare. The proposed system receives, processes, and analyzes cardio data using an Internet-based software platform. The system enables the acquisition of biomedical data using various means of recording cardiac signals located in remote locations around the world. The recorded discretized cardio information is transmitted to the system for processing and mathematical analysis. At the same time, the recorded cardio data can also be stored online in established databases. The article presents the algorithms for the preprocessing and mathematical analysis of cardio data (heart rate variability). The results of studies conducted on the Holter recordings of healthy individuals and individuals with cardiovascular diseases are presented. The created system can be used for the remote monitoring of patients with chronic cardiovascular diseases or patients in remote settlements (where, for example, there may be no hospitals), control and assistance in the process of treatment, and monitoring the taking of prescribed drugs to help to improve people's quality of life. In addition, the issue of ensuring the security of cardio information and the confidentiality of the personal data of health users is considered.

Heart Rate Variability as a Reliable Biomarker Following Concussion: A Critically Appraised Topic

CLINICAL SCENARIO

Recent systematic reviews show conflicting information regarding the effect of concussion on cardiac autonomic function. Controlled aerobic exercise is the most popular intervention for those recovering from a concussion. There is a gap in the literature supporting the utility of objective metrics during exertional return to play protocols and rehabilitation.

CLINICAL QUESTION

Can heart rate variability (HRV) during physical exertion be a reliable biomarker over time for those who suffered a sport-related concussion?

SUMMARY OF KEY FINDINGS

A literature search produced 3 studies relevant to the clinical question. One, a prospective-matched control group cohort study, reported disturbances in HRV during physical exertion in those with a history of concussion, and identified persistent HRV dysfunction after resolution of subjective complaints, return to play, and with multiple concussive events. Second, a cross-sectional cohort study found an HRV difference in those with and without a history of concussion and in HRV related to age and sex. Finally, the prospective longitudinal case-control cohort study did not find sex or age differences in HRV and concluded that, although postconcussion HRV improved as time passed, resting HRV was not as clinically meaningful as HRV during exertional activities.

CLINICAL BOTTOM LINE

There is emerging evidence to support the use of HRV as an observable biomarker, over time, of autonomic function during physical exertion following a sport-related concussion. However, the meaningfulness of HRV data is not fully understood and the utility seems individualized to the level of athlete, age, and sex and, therefore, cannot be generalizable. In order to be more clinically meaningful and to assist with current clinical decision making regarding RTP, a preinjury baseline assessment would be beneficial as an individualized reference for baseline comparison.

STRENGTH OF RECOMMENDATION

Although HRV is not fully understood, currently, there is grade B evidence to support the use of individualized baseline exertional HRV data as comparative objective metric to assess the autonomic nervous system function, over time, following a concussive event.

Dynamic Phase Extraction: Applications in Pulse Rate Variability

Pulse rate variability is a physiological parameter that has been extensively studied and correlated with many physical ailments. However, the phase relationship between inter-beat interval, IBI, and breathing has very rarely been studied. Develop a technique by which the phase relationship between IBI and breathing can be accurately and efficiently extracted from photoplethysmography (PPG) data. A program based on Lock-in Amplifier technology was written in Python to implement a novel technique, Dynamic Phase Extraction. It was tested using a breath pacer and a PPG sensor on 6 subjects who followed a breath pacer at varied breathing rates. The data were then analyzed using both traditional methods and the novel technique (Dynamic Phase Extraction) utilizing a breath pacer. Pulse data was extracted using a PPG sensor. Dynamic Phase Extraction (DPE) gave the magnitudes of the variation in IBI associated with breathing [Formula: see text] measured with photoplethysmography during paced breathing (with premature ventricular contractions, abnormal arrhythmias, and other artifacts edited out). [Formula: see text] correlated well with two standard measures of pulse rate variability: the Standard Deviation of the inter-beat interval (SDNN) (ρ = 0.911) and with the integrated value of the Power Spectral Density between 0.04 and 0.15 Hz (Low Frequency Power or LF Power) (ρ = 0.885). These correlations were comparable to the correlation between the SDNN and the LF Power (ρ = 0.877). In addition to the magnitude [Formula: see text], Dynamic Phase Extraction also gave the phase between the breath pacer and the changes in the inter-beat interval (IBI) due to respiratory sinus arrythmia (RSA), and correlated well with the phase extracted using a Fourier transform (ρ = 0.857). Dynamic Phase Extraction can extract both the phase between the breath pacer and the changes in IBI due to the respiratory sinus arrhythmia component of pulse rate variability ([Formula: see text], but is limited by needing a breath pacer.

A Stochastic Resonance Electrocardiogram Enhancement Algorithm for Robust QRS Detection

This study presents a new QRS detection algorithm making use of the background noise that is inevitably present in electrocardiogram (ECG) recordings. The algorithm suppresses noise, enhances the QRS-waves, and applies a threshold for QRS detection. Noise suppression and QRS enhancement are performed by a band-pass filter stage followed by a nonlinear stage based on the interaction of a particle inside an underdamped monostable potential well. The nonlinear stage maximizes the output when there is a QRS-wave and minimizes the output otherwise. One of the instruments that the nonlinear stage uses to enhance the QRS-waves is stochastic resonance, where the output is maximized for a non-zero intensity background noise. In terms of QRS-wave detection F1 score, which ranges from 98.87% to 99.99% on four major benchmarking databases (MIT-BIH Arrhythmia, QT, European ST-T, and MIT-BIH Noise Stress Test), the algorithm outperforms all existing ECG processing algorithms. The study, for the first time, demonstrates QRS-enhancement by facilitating stochastic resonance while suppressing in-band noise of ECG signals. Detecting QRS-waves as the ECG data streams, having a complexity of O(n), and not requiring any training data make the algorithm convenient for real-time ECG monitoring applications with limited computational resources.

Longitudinal association of early childhood lead exposure and adolescent heart rate variability: influence of parental education

Lead exposure has been shown to dysregulate physiological stress responses. However, few studies have investigated the effect of lead exposure on later heart rate variability (HRV), an indicator of a stress response, in large samples of children. Furthermore, the interaction between social environmental factors and lead exposure in childhood, which commonly co-occur, remains understudied. This study examined relationships between childhood lead exposure and early adolescent physiological stress responses at different levels of parental education. Participants were 406 children from Jintan, China. Blood lead levels (BLLs) and parental education data were collected at 3-5 years of age, and HRV outcomes assessed at 12 years via frequency domain measures (LF/HF ratio) collected during an induced stress test. Results show a significant interaction between parental education and BLLs at 3-5 years. This relationship was found to be most consistent for the interaction between BLLs and mother's years of education for both the planning (β = 0.12, p = 0.046) and speaking (β = 0.11, p = 0.043) phase of the stress task, suggesting that increasing years of mother's education may enhance the deleterious influence of lead exposure on the HRV frequency measure, LF/HF ratio. This research highlights the complexity in lead exposure induced outcomes.

Early childhood lead exposure and adolescent heart rate variability: A longitudinal cohort study

Lead is a known neurotoxicant with many detrimental health effects, including neurocognitive deficits and cardiovascular and metabolic disorders. However, few studies have tested the association between lead exposure and the physiological stress response, which in and of itself may act as a precursor to and/or underlying mechanism of detrimental health outcomes. The purpose of this study was to examine the influence of early childhood and early adolescent low-level lead exposure on early adolescent heart rate variability, a widely-used measure of physiological stress. Participants were 408 children from Jintan, China for whom blood lead levels were measured between 3 and 5 years (early childhood) and again at 12 years (early adolescence). Heart rate variability was assessed at 12 years while participants underwent an induced stress task utilizing the ratio of low to high frequency (LF/HF) ECG measures. Mean blood lead levels in the cohort were 6.63 mcg/dl and 3.10 mcg/dl at 3-5 years and 12 years, respectively. Blood lead levels at 3-5 years of age (β 0.06, p = 0.027), but not at age 12 (β -0.05, p = 0.465), were significantly associated with LF/HF measures while controlling for multiple sociodemographic variables, potentially reflecting a dysregulated stress response with a shift towards sympathetic dominance. These findings suggest that early childhood lead exposure may have a detrimental influence on early adolescent autonomic responses to acute stress, which holds implications for cardiovascular health and overall growth and development.

Heart Rate Variability as a Potential Indicator of Cancer Pain in a Mouse Model of Peritoneal Metastasis

Heart rate variability (HRV) is closely related to changes in the autonomic nervous system (ANS) associated with stress and pain. In this study, we investigated whether HRV could be used to assess cancer pain in mice with peritoneal metastases. At 12 days after cancer induction, positive indicators of pain such as physiological characteristics, appearance, posture, and activity were observed, and time- and frequency-domain HRV parameters such as mean R-R interval, square root of the mean squared differences of successive R-R intervals, and percentage of successive R-R interval differences greater than 5 ms, low frequency (LF), high frequency (HF), and ratio of LF and HF power, were found to be significantly decreased. These parameters returned to normal after analgesic administration. Our results indicate that overall ANS activity was decreased by cancer pain and that HRV could be a useful tool for assessing pain.

The indirect impact of heart rate variability on cold pressor pain tolerance and intensity through psychological distress in individuals with chronic pain: the Tromsø Study

Supplemental Digital Content is Available in the Text. The hypoalgesic impact of cardiovascular regulatory systems on evoked pain responsiveness in those with chronic pain is conveyed via the indirect effects of psychological distress.

Introduction:

Chronic pain (CP) patients often display lower heart rate variability (HRV) and baroreceptor sensitivity (BRS), which are associated with increased evoked pain intensity and decreased pain tolerance.

Objective:

The purpose of this study was to test whether the association between low levels of HRV and BRS and increased evoked pain responsiveness in individuals with CP is mediated by psychological distress and whether this mediation is sex dependent.

Methods:

The sample consisted of 877 participants in Wave 6 of the Tromsø population study who reported clinically meaningful CP. Resting HRV and BRS parameters were derived from continuous beat-to-beat blood pressure recordings. Psychological distress was assessed using the Hopkins Symptom Checklist-10. After cardiovascular assessment, participants completed a 106-second cold pressor task (3°C bath), which assessed cold pressor pain intensity (CPI) and cold pressor pain tolerance (CPT).

Results:

In the full CP sample, mediation analyses showed significant indirect effects, without direct effects, of HRV and BRS on both CPT and CPI via psychological distress. When stratified by sex, significant indirect effects via psychological distress were only found in males for the impact of rMSSD on CPT, the impact of SDNN on CPT, and the impact of BRS on CPT via psychological distress. Moderated mediation analyses revealed that there were no significant sex differences in the indirect effects of HRV and BRS on both CPT and CPI via psychological distress.

Conclusions:

The hypoalgesic impact of cardiovascular regulatory systems on evoked pain responses is conveyed via the indirect effects of psychological distress.

The effects of intrinsic motivation on mental fatigue

There have been many studies attempting to disentangle the relation between motivation and mental fatigue. Mental fatigue occurs after performing a demanding task for a prolonged time, and many studies have suggested that motivation can counteract the negative effects of mental fatigue on task performance. To complicate matters, most mental fatigue studies looked exclusively at the effects of extrinsic motivation but not intrinsic motivation. Individuals are said to be extrinsically motivated when they perform a task to attain rewards and avoid punishments, while they are said to be intrinsically motivated when they do for the pleasure of doing the activity. To assess whether intrinsic motivation has similar effects as extrinsic motivation, we conducted an experiment using subjective, performance, and physiological measures (heart rate variability and pupillometry). In this experiment, 28 participants solved Sudoku puzzles on a computer for three hours, with a cat video playing in the corner of the screen. The experiment consisted of 14 blocks with two alternating conditions: low intrinsic motivation and high intrinsic motivation. The main results showed that irrespective of condition, participants reported becoming fatigued over time. They performed better, invested more mental effort physiologically, and were less distracted in high-level than in low-level motivation blocks. The results suggest that similarly to extrinsic motivation, time-on-task effects are modulated by the level of intrinsic motivation: With high intrinsic motivation, people can maintain their performance over time as they seem willing to invest more effort as time progresses than in low intrinsic motivation.

Cardiopulmonary Activity Monitoring Using Millimeter Wave Radars

Current cardiopulmonary activity monitoring is based on contact devices which cannot be used in extreme cases such as premature infants, burnt victims or rescue operations. In order to overcome these limitations, the use of radar technologies emerges as an alternative. This paper aims to enhance the comprehension that non-contact technologies, in particular radar techniques, offer as a monitoring tool. For this purpose, a modified low cost commercial 122 GHz frequency-modulated continuous-wave (FMCW) radar is used to better fit the current application domain. The radar signals obtained are processed using a classic linear filtering algorithm aiming to separate the breathing from the heartbeat component while preserving signals integrity. In a standoff configuration and with different subject orientations, results show that the signal obtained with the radar can be used to extract not only the respiratory and heartbeat rates, but also the heart rate variability (HRV) sequence. Moreover, results evidence the coupling between breathing and heartbeat, also showing that the HRV sequence obtained can identify the respiratory sinus arrhythmia (RSA) effect. Finally, the radar is tested in a simultaneous multi-target scenario, demonstrating its monitoring capabilities in more complex situations. Nevertheless, there are some challenges left to use the system in a real-life monitoring environments, such as the removal of random body movements.

The effect of early burn injury on sensitivity to future painful stimuli in dairy heifers

Animals that experience painful procedures as neonates are more sensitive to pain later in life. We evaluated whether disbudding with a heated iron at 3 (n = 12), 35 (n = 9), or 56 (n = 20) d of age affected heifers’ pain responses to vaccine injections at 11 mo of age. Heifers responded to the injection procedure with struggling and changes in eye temperature and heart rate variability compared to a sham procedure the day before, and still had a heightened response 6 d later, regardless of disbudding age. However, some heart rate variability indices suggested increased sympathetic dominance in heifers disbudded at 35 d, compared to the other 2 age groups, independent of the injection procedure. We also found that heifers disbudded at 3 or 35 d had a higher mean heart rate after the injection procedure compared to those disbudded at 56 d. We conclude that: (1) heifers find injections aversive; and (2) there is some evidence that disbudding age influences autonomic nervous system activity later in life.

L. L. Pinheiro D, de la Rosa T, G. de Almeida AC, A. Scorza F, A. Scorza C. Propolis as A Potential Disease-Modifying Strategy in Parkinson's Disease: Cardioprotective and Neuroprotective Effects in the 6-OHDA Rat Model

Patients with Parkinson's disease (PD) manifest nonmotor and motor symptoms. Autonomic cardiovascular dysregulation is a common nonmotor manifestation associated with increased morbimortality. Conventional clinical treatment alleviates motor signs but does not change disease progression and fails in handling nonmotor features. Nutrition is a key modifiable determinant of chronic disease. This study aimed to assess the effects of propolis on cardiological features, heart rate (HR) and heart rate variability (HRV) and on nigrostriatal dopaminergic damage, detected by tyrosine hydroxylase (TH) immunoreactivity, in the 6-hydroxydopamine (6-OHDA) rat model of PD. Male Wistar rats were injected bilaterally with 6-OHDA or saline into the striatum and were treated with propolis or water for 40 days. Autonomic function was assessed by time domain parameters (standard deviation of all normal-to-normal intervals (SDNN) and square root of the mean of the squared differences between adjacent normal RR intervals (RMSSD)) of HRV calculated from electrocardiogram recordings. Reductions in HR (p = 1.47×10-19), SDNN (p = 3.42×10-10) and RMSSD (p = 8.2×10-6) detected in parkinsonian rats were reverted by propolis. Propolis attenuated neuronal loss in the substantia nigra (p = 5.66×10-15) and reduced striatal fiber degeneration (p = 7.4×10-5) in 6-OHDA-injured rats, which also showed significant weight gain (p = 1.07×10-5) in comparison to 6-OHDA-lesioned counterparts. Propolis confers cardioprotection and neuroprotection in the 6-OHDA rat model of PD.

Cardio-Diagnostic Assisting Computer System

The mathematical analysis and the assessment of heart rate variability (HRV) based on computer systems can assist the diagnostic process with determining the cardiac status of patients. The new cardio-diagnostic assisting computer system created uses the classic Time-Domain, Frequency-Domain, and Time-Frequency analysis indices, as well as the nonlinear methods (Poincaré plot, Recurrence plot, Hurst R/S method, Detrended Fluctuation Analysis (DFA), Multi-Fractal DFA, Approximate Entropy and Sample Entropy). To test the feasibility of the software developed, 24-hour Holter recordings of four groups of people were analysed: healthy subjects and patients with arrhythmia, heart failure and syncope. Time-Domain (SDNN < 50 ms, SDANN < 100 ms, RMSSD < 17 ms) and Frequency-Domain (the spectrum of HRV in the LF < 550 ms², and HF < 540 ms²) parameter values decreased in the cardiovascular disease groups compared to the control group as a result of lower HRV due to decreased parasympathetic and increased sympathetic activity. The results of the nonlinear analysis showed low values of (SD1 < 56 ms, SD2 < 110 ms) at Poincaré plot (Alpha < 90 ms) at DFA in patients with diseases. Significantly reducing these parameters are markers of cardiac dysfunction. The examined groups of patients showed an increase in the parameters (DET% > 95, REC% > 38, ENTR > 3.2) at the Recurrence plot. This is evidence of a pathological change in the regulation of heart rhythm. The system created can be useful in making the diagnosis by the cardiologist and in bringing greater accuracy and objectivity to the treatment.

Pediatric Clinical Endpoint and Pharmacodynamic Biomarkers: Limitations and Opportunities

Medical research in children typically lags behind that of adult research in both quantity and quality. The conduct of rigorous clinical trials in children can raise ethical concerns because of children's status as a 'vulnerable' population. Moreover, carrying out studies in pediatrics also requires logistical considerations that rarely occur with adult clinical trials. Due to the relatively smaller number of pediatric studies to support evidence-based medicine, the practice of medicine in children is far more reliant upon expert opinion than in adult medicine. Children are at risk of not receiving the same level of benefits from precision medicine research, which has flourished with new technologies capable of generating large amounts of data quickly at an individual level. Although progress has been made in pediatric pharmacokinetics, which has led to safer and more effective dosing, gaps in knowledge still exists when it comes to characterization of pediatric disease and differences in pharmacodynamic response between children and adults. This review highlights three specific therapeutic areas where biomarker development can enhance precision medicine in children: asthma, type 2 diabetes mellitus, and pain. These 'case studies' are meant to update the reader on biomarkers used currently in the diagnosis and treatment of these conditions, and their shortcomings within a pediatric context. Current research on surrogate endpoints and pharmacodynamic biomarkers in the above therapeutic areas will also be described. These cases highlight the current lack in pediatric specific surrogate endpoints and pharmacodynamic biomarkers, as well as the research presently being conducted to address these deficiencies. We finally briefly highlight other therapeutic areas where further research in pediatric surrogate endpoints and pharmacodynamic biomarkers can be impactful to the care of children.

Autonomic Nervous System Is Related to Inhibitory and Control Function Through Functional Inter-Region Connectivities of OFC in Major Depression

OBJECTIVE

To investigate the mechanism of interactions between autonomic nervous system (ANS) and cognitive function in Major depression (MD) with Magnetoencephalography (MEG) measurements.

METHODS

Participants with MD (n = 20), and Health controls (HCs, n = 18) were completed MEG measurements during the performance of a go/no-go task. Heart rate variability (HRV) indices (SDANN, and RMSSD) were derived from the raw MEG data. The correlation analysis of the HRV and functional connectivities in different brain regions was conducted by Pearson's r in two groups.

RESULTS

The go/no-go task performances of HCs were better than MD patients; HRV indices were lower in the MD group. Under the no-go task, a brain MEG functional connectivity analysis based on the seed regions of the orbitofrontal cortex (OFC) displayed increased functional inter-region connectivity networks of OFC in MD group. HRV indices were correlated with different functional inter-region connectivity networks of OFC in two groups, respectively.

CONCLUSION

ANS is related to inhibitory and control function through functional inter-region connectivity networks of OFC in MD. These findings have important implications for the understanding pathophysiology of MD, and MEG may provide an image-guided tool for interventions.

Preliminary Comparison of Zero-Gravity Chair With Tilt Table in Relation to Heart Rate Variability Measurements

Heart rate variability (HRV) measurements are performed using a tilt-table (TT) to diagnose dysfunctionality in the autonomic nervous system (ANS) and the cardiovascular system. To maintain homeostasis, the ANS adapts to body position changes through alterations in sympathetic and parasympathetic responses that can be quantified by extracting time-domain and frequency-domain parameters from the heart rate signal. When body position is changed from supine to erect, a healthy subject’s response also shows changes in ANS activity. However, TT can be unsafe or uncomfortable for elderly or overweight subjects. Furthermore, it may induce anxiety which alters the HRV measurements. This study proposes an alternative strategy to replace the TT with a zero-gravity chair (ZGC). The statistical analysis between HRV parameters from the TT and the ZGC shows that ZGC can be a feasible alternative to TT. Therefore, ZGC can be used as a more convenient, secure, stable and safer option to the traditional HRV analysis with TT.

The Role of Motivation as a Factor in Mental Fatigue

OBJECTIVE

The aim of this study was to assess motivation as a factor in mental fatigue using subjective, performance, and physiological measures.

BACKGROUND

Sustained performance on a mentally demanding task can decrease over time. This decrement has two possible causes: a decline in available resources, meaning that performance cannot be sustained, and decrement in motivation, meaning a decline in willingness to sustain performance. However, so far, few experimental paradigms have effectively and continuously manipulated motivation, which is essential to understand its effect on mental fatigue.

METHOD

Twenty participants performed a working memory task with 14 blocks, which alternated between reward and nonreward for 2.5 hr. In the reward blocks, monetary rewards could be gained for good performance. Besides reaction time and accuracy, we used physiological measures (heart rate variability, pupil diameter, eyeblink, eye movements with a video distractor) and subjective measures of fatigue and mental effort.

RESULTS

Participants reported becoming fatigued over time and invested more mental effort in the reward blocks. Even though they reported fatigue, their accuracy in the reward blocks remained constant but declined in the nonreward blocks. Furthermore, in the nonreward blocks, participants became more distractable, invested less cognitive effort, blinked more often, and made fewer saccades. These results showed an effect of motivation on mental fatigue.

CONCLUSION

The evidence suggests that motivation is an important factor in explaining the effects of mental fatigue.

Parental Bonding in Adolescents With and Without Chronic Pain

Objective

Parental responses influence children's pain; however, the specific role of parental bonding in pediatric pain has not been examined. Depressive symptomology is frequently reported in children with chronic pain (CP) and may play a role in the relationship between parental bonding and pain. This study examined the connections between maternal/paternal bonding (perceived care and control) and symptoms of pain and depression in adolescents with CP and in healthy adolescents.

Method

Participants included 116 adolescents (aged 12-17) with CP (n = 55) and without (n = 61). Adolescents completed the Parental Bonding Instrument separately for their mother and father, as well as measures of depression and pain.

Results

Significant associations between parental bonding and adolescent pain and depression emerged in the pain group, but not in the healthy group. There were no differences in the impact of maternal versus paternal bonding on adolescent pain and depression. Mediation analyses revealed adolescent depression was a mediator of the relationship between maternal care and adolescent pain, and paternal control and adolescent pain in the group with CP.

Conclusions

This study highlights the importance of considering parental bonding and adolescent depression in pediatric CP, suggesting that high paternal control and low maternal care contribute to increased pain in adolescents through heightened adolescent depressive symptoms. The findings emphasize the need for family-based treatment for CP that addresses parent behaviors and adolescent mental health.

Time, frequency and information domain analysis of short-term heart rate variability before and after focal and generalized seizures in epileptic children

OBJECTIVE

In this work we explore the potential of combining standard time and frequency domain indexes with novel information measures, to characterize pre- and post-ictal heart rate variability (HRV) in epileptic children, with the aim of differentiating focal and generalized epilepsy regarding the autonomic control mechanisms.

APPROACH

We analyze short-term HRV in 37 children suffering from generalized or focal epilepsy, monitored 10 s, 300 s, 600 s and 1800 s both before and after seizure episodes. Nine indexes are computed in time (mean, standard deviation of normal-to-normal intervals, root mean square of the successive differences (RMSSD)), frequency (low-to-high frequency power ratio LF/HF, normalized LF and HF power) and information (entropy, conditional entropy and self-entropy) domains. Focal and generalized epilepsy are compared through statistical analysis of the indexes and using linear discriminant analysis (LDA).

MAIN RESULTS

In children with focal epilepsy, early post-ictal phase is characterized by significant tachycardia, depressed HRV, increased LF power and LF/HF, and decreased complexity, progressively recovered across time windows after the episodes. Children with generalized seizures instead show significant tachycardia, lower RMSSD, higher LF power and LF/HF ratio before the seizure. These different behaviors are exploited by LDA analysis to separate focal and generalized epilepsy up to an accuracy of 75%. Results suggest a shift of the sympatho-vagal balance towards sympathetic dominance and vagal withdrawal, noticeable just after the termination of seizure episodes and then reverted in focal epilepsy, and persistent during inter-ictal and pre-ictal periods in generalized epilepsy.

SIGNIFICANCE

Our analysis helps in elucidating the pathophysiology of inter-ictal HRV autonomic control and the differential diagnosis of generalized and focal epilepsy. These findings may have clinical relevance since altered sympatho-vagal control can be related to a higher danger of morbidity and mortality, may reduce thresholds for life-threatening arrhythmias, and could be a biomarker of risk for sudden unexpected death in epilepsy.

Comparison of Physiological and Biochemical Autonomic Indices in Children with and without Autism Spectrum Disorders

Background and objectives: Autism Spectrum Disorder (ASD) is a complex neuro-developmental disorder and it has been suggested that symptoms of ASD are associated with neural networks that regulate the Autonomic Nervous System (ANS). However, the nature of autonomic atypicalities in ASDs remain largely unknown. Measures like Heart Rate Variability (HRV) and urinary Vanillylmandelic Acid (VMA) estimation are sensitive and non-invasive physiological and biochemical indicators of autonomic nervous activity. This study aimed to compare the physiological and biochemical autonomic indices in children with and without ASD. Materials and Methods: In this case-control study, 40 children with autism and 40 Typically Developing (TD) children were recruited. Measures of physiological autonomic index were assessed by the analysis of short term HRV, and the urinary levels of VMA estimation was used as a biochemical autonomic index. Results: Cardiac sympathetic activity assessed by Low Frequency (nu) of HRV was significantly higher in the ASD group in comparison with the TD group (p = 0.006). On the contrary, both the High Frequency (abs) and (nu) of HRV were found to be significantly lower in autistic children (p = 0.034 and p = 0.000) than controls. Autistic children also exhibited a significantly higher level (p = 0.049) of VMA concentration compared to TD children. Conclusion: The study concludes that children with ASD exhibit lower cardio-vagal activity as measured by HRV and increased sympathetic activity as assessed by urinary VMA compared to that of TD children. The core autistic symptoms exhibited by children with ASD could be due to the differences in baseline arousal or stress which might be associated with autonomic dysfunction. Further studies are needed to examine the association of this autonomic dysregulation with ASD symptoms and comorbidities.

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.

Observations of Autonomic Variability Following Central Neuromodulation for Chronic Neuropathic Pain in Spinal Cord Injury

BACKGROUND

Spinal cord injury (SCI) persons with chronic neuropathic pain (NP) demonstrate maladaptive autonomic profiles compared to SCI counterparts without NP (SCI - NP) or able-bodied (AB) controls. These aberrations may be secondary to maladaptive neuroplasticity in the shared circuitry of the pain neuromatrix-central autonomic network interface (PNM-CAN). In this study, we explored the proposed PNM-CAN mechanism in SCI + NP and AB cohorts following centrally-directed neuromodulation to assess if the PNM and CAN are capable of being differentially modulated.

MATERIALS AND METHODS

Central neuromodulation was administered via breathing-controlled electrical stimulation (BreEStim), previously evidenced to operate at the PNM. To quantify CAN activity, conventional heart rate variability (HRV) recordings were used to gather time and frequency domain parameters of autonomic modulation. SCI + NP (n = 10) and AB (n = 13) cohorts received null and active BreEStim randomly in crossover fashion. HRV data were gathered pretest and 30 minutes posttest. Pain modulation was quantified at both time-points by visual analog scale (VAS) for SCI + NP persons and electrical detection and pain threshold levels (EDT, EPT) for AB persons.

RESULTS

Following active BreEStim only, SCI + NP persons demonstrated increased parasympathetic tone (increased NN50, p = 0.03, and pNN50, p = 0.02, HRV parameters). This parasympathetic restoration was associated with analgesia (VAS reduction, p < 0.01). Similarly, AB persons demonstrated increased noxious tolerance (increased EPT, p = 0.03, with preserved EDL, p = 0.78) only following active BreEStim. However, this increased pain threshold was not associated with autonomic changes.

CONCLUSIONS

Central modulation targeting the PNM produced autonomic changes in SCI + NP persons but not AB persons. These findings suggest that AB persons exhibit intact CAN mechanisms capable of compensating for PNM aberrations or simply that SCI + NP persons exhibit altered PNM-CAN machinery altogether. Our collective findings confirm the interconnectedness and maladaptive plasticity of PNM-CAN machinery in SCI + NP persons and suggest that the PNM and CAN circuitry can be differentially modulated.

Motivational Non-directive Resonance Breathing as a Treatment for Chronic Widespread Pain

Chronic widespread pain (CWP) is one of the most difficult pain conditions to treat due to an unknown etiology and a lack of innovative treatment design and effectiveness. Based upon preliminary findings within the fields of motivational psychology, integrative neuroscience, diaphragmatic breathing, and vagal nerve stimulation, we propose a new treatment intervention, motivational non-directive (ND) resonance breathing, as a means of reducing pain and suffering in patients with CWP. Motivational ND resonance breathing provides patients with a noninvasive means of potentially modulating five psychophysiological mechanisms imperative for endogenously treating pain and increasing overall quality of life.

Cerebral blood flow and heart rate variability predict fatigue severity in patients with chronic fatigue syndrome

Prolonged, disabling fatigue is the hallmark of chronic fatigue syndrome (CFS). Previous neuroimaging studies have provided evidence for nervous system involvement in CFS etiology, including perturbations in brain structure/function. In this arterial spin labeling (ASL) MRI study, we examined variability in cerebral blood flow (CBFV) and heart rate (HRV) in 28 women: 14 with CFS and 14 healthy controls. We hypothesized that CBFV would be reduced in individuals with CFS compared to healthy controls, and that increased CBFV and HRV would be associated with lower levels of fatigue in affected individuals. Our results provided support for these hypotheses. Although no group differences in CBFV or HRV were detected, greater CBFV and more HRV power were both associated with lower fatigue symptom severity in individuals with CFS. Exploratory statistical analyses suggested that protective effects of high CBFV were greatest in individuals with low HRV. We also found novel evidence of bidirectional association between the very high frequency (VHF) band of HRV and CBFV. Taken together, the results of this study suggest that CBFV and HRV are potentially important measures of adaptive capacity in chronic illnesses like CFS. Future studies should address these measures as potential therapeutic targets to improve outcomes and reduce symptom severity in individuals with CFS.

Neuropathic pain modulation after spinal cord injury by breathing-controlled electrical stimulation (BreEStim) is associated with restoration of autonomic dysfunction

BACKGROUND

Recent findings have implicated supraspinal origins from the pain neuromatrix- central autonomic network (PNM-CAN) in the generation of neuropathic pain (NP) after spinal cord injury (SCI). The aim of this study was to further investigate the theorized PNM-CAN mechanisms in persons with SCI by using a centrally directed pain intervention, provided by breathing-controlled electrical stimulation (BreEStim), to measure resultant autonomic changes measured by time and frequency domain heart rate variability (HRV) analysis.

METHODS

Null and active BreEStim interventions were administered to SCI+NP subjects (n=10) in a random order. HRV data and VAS pain scores were collected at resting pre-test and 30 minutes post-test time points. Resting HRV data were also collected from SCI-NP subjects (n=11).

RESULTS

SCI+NP subjects demonstrated a lower baseline HRV and parasympathetic tone, via SD of the normal-to-normal intervals (SDNN) and low frequency (LF) parameters, compared with SCI-NP subjects. However, following active BreEStim, SCI+NP subjects exhibited an increase in HRV and parasympathetic tone, most notably via pairs of successive R-R beat lengths varying by greater than 50 ms (NN50) and proportion of NN50 for total number of beats (pNN50) parameters along with lower VAS scores. Additionally, the post-test SCI+NP group was found to have a statistically comparable autonomic profile to the SCI-NP group across all HRV variables, including SDNN and LF parameters.

CONCLUSION

The analgesic effects of active BreEStim in SCI+NP subjects were associated with restoration of autonomic dysfunction in this population.

Novice Meditators of an Easily Learnable Audible Mantram Sound Self-Induce an Increase in Vagal Tone During Short-term Practice: A Preliminary Study

INTRODUCTION

The autonomic nervous system (ANS) plays a vital role in regulation of the physiological processes during normal and pathological conditions. Heart rate variability (HRV) is regarded as a major indicator of the self-regulatory strength and balance of parasympathetic nervous system (PNS) and sympathetic nerve system (SNS) impulses, as interpreted by the intrinsic nervous system of the heart. The present study focuses on the evaluation of the effects of audible and mindful practice of chanting meditation on HRV and on the cognitive disposition.

METHODOLOGY

The subjects were randomly assigned to 2 different sounds based on monotone repetition. One was the Hare Krishna Mantram (HKM-Sanskrit experimental sound) and the other was a concocted sound (Sanskrit placebo). Changes in vagal tone were measured with respect to both time domain and frequency domains. Five-min baseline and postmeditation measurements were obtained on different days over the next 6 wk. The subjects who chanted the placebo/sham sound switched to the experimental sound at the 4-wk mark for the next 2 wk. All subjects completed an experience survey.

RESULTS

Paired t test results for all HRV parameters achieved statistical significance in the test group. Statistical significance in all the aforementioned measures of HRV was also observed on switching the control group placebo sound chanting to the experimental sound. HRV wave forms showed relaxation, a pattern and experience survey suggests an increase in attributes associated with higher self-regulation.

CONCLUSION

This study suggests statistically significant efficacy data and that a larger randomized study is feasible to test the potential of the audible repetition of the HKM in clinical settings. It may therefore enable beneficial lifestyle for health creation and thus play a role in the prevention of chronic diseases. Further, large scale studies are required for a better perspective on the effect of mantram repetition on the HRV.

Emotion regulation and positive affect in the context of salivary alpha-amylase response to pain in children with cancer

BACKGROUND

Children with cancer routinely undergo painful medical procedures invoking strong physiological stress responses. Resilience to this pain may be conferred through resources such as emotion regulation strategies and positive affect.

PROCEDURE

This study measured dispositional positive affect in children with cancer (N = 73) and randomly assigned participants to one of three emotion regulation strategy conditions (distraction, reappraisal, or reassurance). Children applied their assigned strategy during an experimental pain procedure (the cold pressor task [CPT]) and provided saliva samples before, immediately after, and 15 min after the CPT. Saliva samples were later assayed for salivary alpha amylase (sAA)-a surrogate marker for autonomic/sympathetic nervous system activity and regulation.

RESULTS

Children in the reassurance group had sAA levels that continued to rise after completion of the CPT compared to children in the distraction (b = -1.68, P = 0.021) and reappraisal conditions (b = -1.24, P = 0.084). Furthermore, dispositional positive affect moderated the effect of condition such that children in the reassurance group with lower levels of positive affect had sAA levels that continued to rise after completion of the CPT (dy/dx = 1.56, P = 0.027), whereas children in the reassurance condition with higher levels of positive affect did not exhibit this rise (P > 0.05).

CONCLUSIONS

Specific emotion regulation strategies, such as distraction and reappraisal, may attenuate the stress response to pain in pediatric patients with cancer, and positive affect may confer resilience in response to pain even with use of less effective coping strategies such as reassurance.

Effect of excessive infant crying on resting BP, HRV and cardiac autonomic control in childhood

Objective

Early life stress has been shown to influence the developing autonomic nervous system. Stressors in infancy may program the autonomic nervous system resting state set point, affecting cardiovascular function in later life. Excessive crying may be an indicator of increased stress arousal in infancy. We hypothesized that excessive infant crying is related to altered cardiac autonomic nervous system activity and increased blood pressure at age 5–6 years.

Methods

In the Amsterdam Born Children and their Development study, excessive crying, maternal burden of infant care and maternal aggressive behavior in the 13^th week after birth (range 11–16 weeks) were reported using questionnaires. Blood pressure, heart rate, heart rate variability and indicators of cardiac autonomic nervous system activity (sympathetic drive by pre-ejection period, parasympathetic drive by respiratory sinus arrhythmia) were measured at age 5–6 years during rest. Inclusion criteria were singleton birth, term-born, and no reported congenital or cardiovascular problems (N = 2153 included).

Results

Excessive crying (2.8%) was not associated with resting heart rate, heart rate variability, pre-ejection period, respiratory sinus arrhythmia nor with blood pressure at age 5–6 years.

Conclusions

Excessive infant crying as an indicator of increased stress arousal does not seem to be related to resting activity of the autonomic nervous system or blood pressure at age 5–6. Potential associations may become visible under stressed conditions.

Therapeutic Basis of Clinical Pain Modulation

Pain is a hallmark of almost all bodily ailments and can be modulated by agents, including analgesics and anesthetics that suppress pain signals in the central nervous system. Defects in the modulatory systems, including the endogenous pain-inhibitory pathways, are a major factor in the initiation and chronicity of pain. Thus, pain modulation is particularly applicable to the practice of medicine. This review summarizes the existing literature on pain modulation. Here, we critically reviewed the literature from PubMed on pain modulation published primarily within the past 5 years in high impact journals. Specifically, we have discussed important anatomical landmarks of pain modulation and outlined the endogenous networks and underlying mechanisms of clinically relevant pain modulatory methods. The Gate Control Theory is briefly presented with discussion on the capacity of pain modulation to cause both hyper- and hypoalgesia. An emphasis has been given to highlight key areas in pain research that, because of unanswered questions or therapeutic potential, merit additional scientific scrutiny. The information presented in this paper would be helpful in developing novel therapies, metrics, and interventions for improved patient management.

Photoplethysmography variability as an alternative approach to obtain heart rate variability information in chronic pain patient

Heart rate variability (HRV) is a well-known method for the assessment of autonomic nervous function of the heart. Previous study suggested that pulse rate variability (PRV) determined by photoplethysmography could be used instead of HRV to more simply assess autonomic nervous function. However, most research studies included healthy subjects. Thus, the aim of this study was to investigate the feasibility for PRV as a surrogate index for patients with chronic pain. This study investigated the correlation coefficient (by Pearson correlation) and agreement (by Bland-Altman analysis) between PRV and HRV in chronic pain patients in the clinical setting. The results showed high significant correlations (p < 0.001, r > 0.86) between all the HRV and PRV parameters and good agreements (ratio < 0.1) between the parameters in terms of HR, mean RR, VLF, LF, nLF, nHF, and SD1/SD2. Our study suggests that HRV can also be reliably estimated using the photoplethysmography-based PP interval in elderly patients with chronic pain.

Diminished vagal tone is a predictive biomarker of necrotizing enterocolitis-risk in preterm infants

BACKGROUND

Necrotizing enterocolitis (NEC) is an acute neonatal inflammatory disease which may lead to intestinal necrosis, multisystem failure, and death. Currently, NEC is diagnosed by a combination of laboratory and radiographic tests conducted a posteriori i.e., when NEC is already clinically significant. Given the acute onset and rapid progression of NEC, a non-invasive biomarker that allows early detection of patients at risk is required as a matter of urgency. We evaluated whether the high frequency (HF) component of heart rate variability (HRV), a measure of vagal efferent tonic cholinergic activity may be used as a predictive biomarker for NEC-risk before the onset of clinical disease.

METHODS

In this prospective study, stable preterm (gestational age 28-35 weeks) infants had HRV power spectra analyzed from surface electrocardiogram waveforms taken at rest on day 5-8 of life. We used regression modeling to determine the utility of HF-HRV in predicting NEC.

KEY RESULTS

HF-HRV power was 21.5 ± 2.7 and 3.9 ± 0.81 ms(2) in infants that remained healthy and those that later developed stage 2+ NEC, respectively (p < 0.001). Nine of 70 enrolled infants developed NEC. The ROC discriminated a HF-HRV value of 4.68 ms(2) predictive for developing NEC with a sensitivity and specificity of 89% and 87%, and positive and negative predictive value of 50% and 98%, respectively. With predictive regression modeling, the risk (odds ratio) of developing NEC was 10 per every one SD decrease in HF-HRV.

CONCLUSIONS & INFERENCES

Our preliminary data indicate that HF-HRV may serve as a potential, non-invasive predictive biomarker of NEC-risk in NICU infants.

A practical guide and perspectives on the use of experimental pain modalities with children and adolescents

Use of experimental pain is vital for addressing research questions that would otherwise be impossible to examine in the real world. Experimental induction of pain in children is highly scrutinized given the potential for harm and lack of direct benefit to a vulnerable population. However, its use has critically advanced our understanding of the mechanisms, assessment and treatment of pain in both healthy and chronically ill children. This article introduces various experimental pain modalities, including the cold pressor task, the water load symptom provocation test, thermal pain, pressure pain and conditioned pain modulation, and discusses their application for use with children and adolescents. It addresses practical implementation and ethical issues, as well as the advantages and disadvantages offered by each task. The incredible potential for future research is discussed given the array of experimental pain modalities now available to pediatric researchers.