High-frequency modulation of heart rate variability during exercise in patients with COPD

Assessing the importance and safety of hypoxia conditioning for patients with occupational pulmonary diseases: A recent clinical perspective

Occupational pulmonary diseases (OPDs) pose a significant global health challenge, contributing to high mortality rates. This review delves into the pathophysiology of hypoxia and the safety of intermittent hypoxic conditioning (IHC) in OPD patients. By examining sources such as PubMed, Relemed, NLM, Scopus, and Google Scholar, the review evaluates the efficacy of IHC in clinical outcomes for OPD patients. It highlights the complexities of cardiovascular and respiratory regulation dysfunctions in OPDs, focusing on respiratory control abnormalities and the impact of intermittent hypoxic exposures. Key areas include the physiological effects of hypoxia, the role of hypoxia-inducible factor-1 alpha (HIF-1α) in occupational lung diseases, and the links between brain ischemia, stroke, and OPDs. The review also explores the interaction between intermittent hypoxic exposures, mitochondrial energetics, and lung physiology. The potential of IHE to improve clinical manifestations and underlying pathophysiology in OPD patients is thoroughly examined. This comprehensive analysis aims to benefit molecular pathologists, pulmonologists, clinicians, and physicians by enhancing understanding of IHE's clinical benefits, from research to patient care, and improving clinical outcomes for OPD patients.

Oxidative stress associated with impaired autonomic control and severity of lung function in chronic obstructive pulmonary disease patients

Oxidative stress has been suggested to play a role in the pathogenesis of chronic obstructive pulmonary disease (COPD). This study aimed to investigate a link between malondialdehyde (MDA) levels, pulmonary function, and cardiac autonomic control in patients with COPD. Plasma levels of MDA, heart rate variability, and pulmonary function were measured in 50 clinically stable COPD patients and 50 normal male controls. COPD patients exhibited lower means of the standard deviations of all normal to normal (NN) intervals (SDNN), the square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD), and high frequency (HF). Nevertheless, they presented greater low frequency (LF) and low frequency/high frequency ratio (LF/HF ratio) in supine and head-up tilt positions than controls (P<0.001). More-over, a negative correlation between MDA levels with SDNN (P<0.001) and a positive correlation with LF (P<0.01) and LF/HF ratio (P<0.05) were observed in both positions. In COPD patients, plasma MDA levels were 2.3 times greater than controls (4.33±2.03 μM vs. 1.89±0.39 μM, P<0.001), and they were inversely correlated with forced vital capacity, forced expiratory volume in 1 sec, midexpiratory flow, and peak expiratory flow (P<0.001). Our findings suggest a potential role for oxidative stress in impaired cardiac autonomic control and clinical relevance of plasma MDA levels as a predictor of severity of COPD in COPD patients.

A systematic review and meta-analysis of heart rate variability in COPD

Background

Chronic obstructive pulmonary disease (COPD) is associated with disruption in autonomic nervous control of the heart rhythm. We present here quantitative evidence of the reduction in HRV measures as well as the challenges to clinical application of HRV in COPD clinics.

Method

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we search in June 2022 Medline and Embase databases for studies reporting HRV in COPD patients using relevant medical subject headings (MeSH) terms. The quality of included studies was assessed using the modified version of the Newcastle-Ottawa Scale (NOS). Descriptive data were extracted, while standardized mean difference was computed for changes in HRV due to COPD. Leave-one-out sensitivity test was performed to assess exaggerated effect size and funnel plots to assess publication bias.

Results

The databases search yielded 512 studies, of which we included 27 that met the inclusion criteria. The majority of the studies (73%) had a low risk of bias and included a total of 839 COPD patients. Although there were high between-studies heterogeneity, HRV time and frequency domains were significantly reduced in COPD patients compared with controls. Sensitivity test showed no exaggerated effect sizes and the funnel plot showed general low publication bias.

Conclusion

COPD is associated with autonomic nervous dysfunction as measured by HRV. Both sympathetic and parasympathetic cardiac modulation were decreased, but there is still a predominance of sympathetic activity. There is high variability in the HRV measurement methodology, which affects clinical applicability.

Analysis of Reasonable Respiratory Efficiency in Tennis Competition and Training Environment Based on Cloud Computing

Competitive tennis is developing in the direction of quantification. How to use and give full play to all positive factors, in order to attack actively and give full play to the limits of body and psychology, breathing, as the basic metabolic function of human body, also plays a vital role in tennis. This paper studies that it plays an important role in the rationality and explosiveness of sports and the psychological and physiological regulation in competition. The characteristics of tennis events determine the importance of scientific and rational breathing. Reasonable breathing during exercise is conducive to maintaining the basic stability of the internal environment, improving the training effect, and giving full play to the functional ability of the human body, so as to create excellent sports results. First, reduce respiratory resistance. Second, there are two methods to improve alveolar ventilation efficiency and pulmonary ventilation: increasing respiratory rate and increasing respiratory depth. When the inhalation volume is constant, the alveolar gas freshness rate depends on the functional residual volume in the alveolar cavity at the end of expiratory or before inhalation. The less functional the residual air, the more fresh air inhaled, and the higher the oxygen partial pressure in alveolar gas. An effective way to reduce the functional residual volume in the alveolar cavity is to exhale as deeply as possible, so as to ensure that more oxygen enters the body. Reasonable breathing methods can not only accelerate the excitation of the body, increase movement strength, reduce fatigue, and promote recovery but also play a vital role in the rational allocation of physical fitness and the improvement of sports performance. The purpose of this study is to provide a theoretical basis for scientific tennis training by analyzing the characteristics of tennis events, the form of breathing in tennis and the efficiency of reasonable breathing in tennis.

Use of a Wearable Biosensor to Study Heart Rate Variability in Chronic Obstructive Pulmonary Disease and Its Relationship to Disease Severity

The purpose of this study was to explore the relationships between heart rate variability (HRV) and various phenotypic measures that relate to health and functional status in chronic obstructive pulmonary disease (COPD), and secondly, to demonstrate the feasibility of ascertaining HRV via a chest-worn wearable biosensor in COPD patients. HRV analysis was performed using SDNN (standard deviation of the mean of all normal R-R intervals), low frequency (LF), high frequency (HF), and LF/HF ratio. We evaluated the associations between HRV and COPD severity, class of bronchodilator therapy prescribed, and patient reported outcomes. Seventy-nine participants with COPD were enrolled. There were no differences in SDNN, HF, and LF/HF ratio according to COPD severity. The SDNN in participants treated with concurrent beta-agonists and muscarinic antagonists was lower than that in other participants after adjusting heart rate (beta coefficient −3.980, p = 0.019). The SDNN was positively correlated with Veterans Specific Activity Questionnaire (VSAQ) score (r = 0.308, p = 0.006) and handgrip strength (r = 0.285, p = 0.011), and negatively correlated with dyspnea by modified Medical Research Council (mMRC) questionnaire (r = −0.234, p = 0.039), health status by Saint George’s Respiratory Questionnaire (SGRQ) (r = −0.298, p = 0.008), symptoms by COPD Assessment Test (CAT) (r = −0.280, p = 0.012), and BODE index (r = −0.269, p = 0.020). When measured by a chest-worn wearable device, reduced HRV was observed in COPD participants receiving inhaled beta-sympathomimetic agonist and muscarinic antagonists. HRV was also correlated with various health status and performance measures.

Can Reactivity of Heart Rate Variability Be a Potential Biomarker and Monitoring Tool to Promote Healthy Aging? A Systematic Review With Meta-Analyses

Background: Monitoring phasic responses of heart rate variability (HRV) in terms of HRV reactivity [i. e., the absolute change from resting state to on-task (i.e., absolute values of HRV measured during exercise)] might provide useful insights into the individual psychophysiological responses of healthy middle-aged to older adults (HOA) to cognitive and physical exercises. Objectives: To summarize the evidence of phasic HRV responses to cognitive and physical exercises, and to evaluate key moderating factors influencing these responses. Methods: A systematic review with meta-analyses was performed. Publications up to May 2020 of the databases Medline (EBSCO), Embase, Cochrane Library, CINAHL, Psycinfo, Web of Science, Scopus, and Pedro were considered. Controlled clinical trials and observational studies measuring phasic HRV responses to cognitive and/or physical exercises in HOA (≥50 years) were included. Results: The initial search identified 6,828 articles, of which 43 were included into the systematic review. Compared to resting state, vagally-mediated HRV indices were significantly reduced during all types of exercises [Hedge's g = -0.608, 95 % CI (-0.999 to -0.218), p = 0.002] indicating a significant parasympathetic withdrawal compared to rest. The key moderating variables of these responses identified included exercise intensity for physical exercises, and participant characteristics (i.e., level of cognitive functioning, physical fitness), task demands (i.e., task complexity and modality) and the individual responses to these cognitive challenges for cognitive exercises. In particular, higher task demands (task complexity and physical exercise intensity) were related to larger HRV reactivities. Better physical fitness and cognition were associated with lower HRV reactivities. Additionally, HRV reactivity appeared to be sensitive to training-induced cognitive and neural changes. Conclusion: HRV reactivity seems to be a promising biomarker for monitoring internal training load and evaluating neurobiological effects of training interventions. Further research is warranted to evaluate the potential of HRV reactivity as a monitoring parameter to guide cognitive-motor training interventions and/or as a biomarker for cognitive impairment. This may facilitate the early detection of cognitive impairment as well as allow individualized training adaptations that, in turn, support the healthy aging process by optimizing individual exercise dose and progression of cognitive-motor training.

Effects of oxygen supplementation in autonomic nervous system function during exercise in patients with idiopathic pulmonary fibrosis and exertional desaturation

INTRODUCTION

Patients with idiopathic pulmonary fibrosis (IPF) have reduced exercise capacity and often present exertional dyspnea and desaturation. The role of autonomic nervous system (ANS) as a pathogenetic contributor to this dysfunction has not been evaluated.

OBJECTIVE

To evaluate whether improvement of arterial oxygen saturation (SpO₂ ) via oxygen supplementation results to ANS function improvement, during steady state submaximal exercise.

METHODS

This is a secondary analysis of a single-blind, randomized, placebo-controlled, cross-over trial, including 12 IPF patients, with isolated exertional desaturation. Following a maximal cardiopulmonary test, participants underwent two submaximal steady state tests during which they received either supplementary oxygen or medical air. Continuous beat-to-beat blood pressure measurements were recorded (Finapres Medical Systems, Amsterdam, The Netherlands). Autonomic function was assessed non-invasively by heart rate variability (HRV); root mean square of successive differences (RMSSD) and standard-deviation-Poincare-plot (SD1) were used as indices of parasympathetic output. Entropy and detrended fluctuation analysis (DFA) were also used.

RESULTS

During rest, oxygen supplementation did not significantly alter RMSSD and SD1. During exercise, subjects presented no significant alterations compared with baseline, in most HRV indices examined. There was no improvement of this behavior with O₂ -supplementation. Approximate-entropy increased during exercise, with no differences between protocols.

CONCLUSIONS

IPF patients presented an inadequate adaptive response of their ANS to exercise and recovery. Although oxygen supplementation significantly prolonged exercise duration and prevented the substantial exertional desaturation, the blunted vagal response to steady-state exercise in these patients was not improved, suggesting that acute oxygen supplementation does not sufficiently improve ANS dysfunction in these patients.

A novel approach towards non-obstructive detection and classification of COPD using ECG derived respiration

The alarming rate of mortality and disability due to Chronic Obstructive Pulmonary Disease (COPD) has become a serious health concern worldwide. The progressive nature of this disease makes it inevitable to detect this disease in its early stages, leads to a greater demand for developing non-obstructive and reliable technology for COPD detection. The use of highly patient-effort dependent, time-consuming, and expensive methods are some major inherent limitations of previous techniques. Lack of knowledge about the disease and inadequacy of proper diagnostic tool for early detection of COPD is another reason behind the 3rd leading cause of death worldwide. For this reason, this study aims to explore the utility of ECG Derived Respiration (EDR) for classification between COPD patients and normal healthy subjects as EDR can be easily extracted from ECG. ECG and respiration signals collected from 30 normal and 30 COPD subjects were analysed. Error calculation and statistical analysis were performed to observe the similarity between original respiration and EDR signal. The morphological pattern changes of respiration and EDR signals were analysed and three different features were extracted from those. Classification was performed by different classifiers employing Decision Tree, Linear Discriminant Analysis (LDA), Support Vector Machine (SVM) and K-Nearest Neighbor (KNN). Apart from obtaining comparable classification performance it was seen that EDR has better potential than the original respiration signal for classification of COPD from normal population.

Influence of physical rehabilitation on heart rate dynamics in patients with idiopathic pulmonary fibrosis

This study sought to determine whether a 6-week physical rehabilitation programme has a measurable influence on heart rate responsiveness to changing metabolic demand in patients with pulmonary fibrosis. Fifteen individuals (13 with idiopathic pulmonary fibrosis and two with pulmonary fibrosis associated with rheumatoid disease) underwent assessments of physical function (6-min walk test), ventilatory function (spirometry), and cardio-respiratory function (respiratory gas analysis and electrocardiogram [ECG] recording during a protocol consisting of periods of rest, incremental bicycle exercise to maximal effort, and post-exercise recovery). RR (beat-to-beat cardiac intervals) data were derived from the ECG and used to quantify (a) heart rate variability (HRV) and (b) cardiac acceleration (AC) and deceleration capacities (DC) (via phase rectified signal averaging). Following the rehabilitation programme, heart rate was elevated by 11%–18% during exercise and recovery states. HRV was not statistically influenced by rehabilitation during any stage of the assessment protocol; however, qualitative changes were apparent with HRV increasing by 68%–75% during all stages of the protocol. Statistically, AC and DC were similar pre- and postrehabilitation (AC=−2.7 and −3.2 msec; DC=2.3 and 3.2 msec, respectively) but again we observed qualitative improvements in these indices of 19% and 38%, respectively. These results provide initial evidence that physical rehabilitation improves heart rate dynamics (via modulation of autonomic control of heart rate) in idiopathic pulmonary fibrosis patients, even when respiratory and physical functions are unchanged or diminished.

Effects of Water-Based Aerobic Interval Training in Patients With COPD: A RANDOMIZED CONTROLLED TRIAL

PURPOSE

Chronic obstructive pulmonary disease promotes systemic repercussions, which can be minimized with physical exercise. This study investigated the effects of a water-based aerobic interval training program on the autonomic modulation of heart rate (HR), quality of life (QoL), and functional capacity (FC) of patients with chronic obstructive pulmonary disease.

METHODS

Nineteen patients with chronic obstructive pulmonary disease were enrolled in this randomized clinical trial and allocated to either the usual care group (n = 9) or training group (n = 10). Before and after 24 sessions of water-based physical training, the patients underwent evaluation of autonomic modulation of HR by analyzing the HR variability, QoL using the St George's Respiratory Questionnaire, and FC using 6-min walk test distance.

RESULTS

The results showed significant improvement when comparing the variables of HR variability, QoL, and FC in the training group in the pre- and post-training conditions (P < .05). In the usual care group, there was no significant difference for any of the variables. Negative correlations were found between HR variability and QoL (r =-0. 55; P = .01) and 6-min walk test distance and QoL (r =-0.49; P = .02).

CONCLUSION

Water-based physical training promoted beneficial adaptations in the autonomic modulation of HR, QoL, and FC of patients with chronic obstructive pulmonary disease.

Effort Oxygen Saturation and Effort Heart Rate to Detect Exacerbations of Chronic Obstructive Pulmonary Disease or Congestive Heart Failure

Background: current algorithms for the detection of heart failure (HF) and chronic obstructive pulmonary disease (COPD) exacerbations have poor performance. Methods: this study was designed as a prospective longitudinal trial. Physiological parameters were evaluated at rest and effort (walking) in patients who were in the exacerbation or stable phases of HF or COPD. Parameters with relevant discriminatory power (sensitivity (Sn) or specificity (Sp) ≥ 80%, and Youden index ≥ 0.2) were integrated into diagnostic algorithms. Results: the study included 127 patients (COPD: 56, HF: 54, both: 17). The best algorithm for COPD included: oxygen saturation (SaO₂) decrease ≥ 2% in minutes 1 to 3 of effort, end-of-effort heart rate (HR) increase ≥ 10 beats/min and walking distance decrease ≥ 35 m (presence of one criterion showed Sn: 0.90 (95%, CI(confidence interval): 0.75–0.97), Sp: 0.89 (95%, CI: 0.72–0.96), and area under the curve (AUC): 0.92 (95%, CI: 0.85–0.995)); and for HF: SaO₂ decrease ≥ 2% in the mean-of-effort, HR increase ≥ 10 beats/min in the mean-of-effort, and walking distance decrease ≥ 40 m (presence of one criterion showed Sn: 0.85 (95%, CI: 0.69–0.93), Sp: 0.75 (95%, CI: 0.57–0.87) and AUC 0.84 (95%, CI: 0.74–0.94)). Conclusions: effort situations improve the validity of physiological parameters for detection of HF and COPD exacerbation episodes.

Are heart rate dynamics in the transition from rest to submaximal exercise related to maximal cardiorespiratory responses in COPD?

BACKGROUND

Poor exercise capacity is an important negative prognostic marker in patients with chronic obstructive pulmonary disease (COPD). Heart rate variability (HRV) responses can indicate alterations in cardiac autonomic control. Nevertheless, it remains unclear whether these abnormalities are related to cardiorespiratory responses to exercise in these patients.

OBJECTIVE

To evaluate whether HRV at rest and submaximal exercise are related to impaired cardiopulmonary responses to exercise in COPD patients.

METHODS

Fifteen men (66.2±8.7 years) with COPD (FEV1: 55.1±19.2%) were assessed. The R-R interval (RRi) data collection was performed at rest (stand position) and during the six-minute walk test (6MWT). All patients performed a symptom-limited cardiopulmonary exercise test on a cycle ergometer. The HRV changes from rest to submaximal exercise (Δ rest-6MWT) were calculated.

RESULTS

We found significant correlations between low frequency (LF) and high frequency (HF) Δ rest-6MWT with Δ oxyhemoglobin saturation by pulse oximetry (r=-0.64 and r=0.65, respectively; p<0.05), minute ventilation/carbon dioxide output relationship from beginning to peak exercise (r=-0.52 and r=0.53, p<0.05), and exercise ventilatory power (r=0.52 and r=-0.53, p<0.05). Interestingly, there was a strong positive correlation (r=0.82, p<0.05) between six-minute walk distance (6MWD) and Δ LF/HF from rest to exercise.

CONCLUSION

HRV analysis in the transition from rest to submaximal exercise is associated with exercise ventilatory and hemodynamic abnormalities in COPD patients. Rehabilitative strategies to improve HRV responses may provide an important tool to clinical practice in these patients.

Effect of lung transplantation on heart rate response to exercise

OBJECTIVES

To evaluate if patients have a change in percent of predicted heart rate reserve used at peak exercise (%HRR) after lung transplantation, even at matching workloads.

BACKGROUND

Lung disease of obstructive, restrictive, and mixed types may be associated with an autonomic imbalance. Lung transplantation may improve the effects of pulmonary disease on cardiac function. However, the effect of lung transplantation on heart rate responses during exercise has not been investigated in detail.

METHODS

Retrospective review of patients who underwent lung transplantation. Pre and post transplant cardiopulmonary exercise tests were reviewed.

RESULTS

The %HRR significantly improved by a median of 37% (p < 0.001) following lung transplantation. When matching workloads were analyzed, the %HRR also decreased from a median of 36% to 24% (p < 0.001).

CONCLUSIONS

Corresponding to an increase in peak exercise capacity, percentage of heart rate reserve used improves significantly after lung transplantation, even at matching workloads, indicating a likely improvement in autonomic modulation.

Chronotropic incompetence predicts mortality in severe obstructive pulmonary disease

We evaluated the prevalence of chronotropic incompetence (CI), a marker of autonomic dysfunction, and its prognostic value in patients with chronic obstructive pulmonary disease (COPD). We performed a retrospective analysis of 449 patients with severe COPD who underwent a cardiopulmonary exercise test, after excluding patients with lung volume reduction surgery, left ventricular dysfunction and those not in sinus rhythm. CI was defined as percent predicted heart rate reserve (%HRR). Events were defined as death or lung transplant during a median follow-up of 68 months. Median age was 61 years; median percent predicted forced expiratory volume in one second (%FEV1) of 25% and median %HRR of 33%. The hazard ratio for an event in the lowest quartile of %HRR, taking the highest quartile as reference, was of 3.2 (95% confidence interval: 2.1-4.8; p<0.001). In a multivariate regression model, %HRR was an independent predictor of events. In conclusion, CI was an independent and powerful outcome predictor in patients with severe COPD.

The effect of anxiety on heart rate variability, depression, and sleep in chronic obstructive pulmonary disease

OBJECTIVES

The current study investigates heart rate variability (HRV) responses to a psychosocial stressor in chronic obstructive pulmonary disease (COPD) patients, and the potential role of anxiety as a confounding factor in this relationship. Additionally, this study also investigates the influence of anxiety on sleep and depressive symptoms among COPD patients.

METHODS

The study utilized a 2 (disease status)×2 (anxiety group) factorial design examining HRV associated with anxiety symptoms and COPD during a standardized acute social stress task. Participants (mean age 59.1±11.2 years; 50% female) completed pulmonary function testing, HRV monitoring, and self-report questionnaires assessing psychological factors. 30 COPD patients were age- and gender-matched with 30 healthy controls.

RESULTS

HRV response to a psychosocial stressor among participants with higher anxiety (both COPD and healthy) reflected autonomic dysregulation in both time and frequency domains that was not evident among non-anxious participants. COPD participants with higher anxiety reported greater symptoms of depression and poorer sleep quality than did COPD participants with low anxiety.

CONCLUSIONS

Anxiety is associated with dysregulated HRV response to a psychosocial stressor, but the negative influence of anxiety and COPD on autonomic function did not appear to be additive. Comorbid anxiety in patients with COPD is associated with increased behavioral and psychological symptoms of distress.

Nonlinear interaction of voluntary breathing and cardiovascular regulation

To investigate the effects of voluntary breathing on respiratory sinus arrhythmia and nonlinearity of heart rate variability (HRV), two kinds of voluntary breathing, speech and breath-holding, were used. The results showed that both types of voluntary breathing diminished the high frequency component of HRV, but speech decreased, while breath-holding enhanced the nonlinearity of HRV as detected by the Volterra series method. This finding indicates that respiratory patterns have a variety of influences on cardiovascular regulation.

C-reactive protein, lung hyperinflation and heart rate variability in chronic obstructive pulmonary disease --a pilot study

Chronic obstructive pulmonary disease (COPD) is associated to cardiovascular morbidity and mortality, and abnormalities of the autonomic nervous system have been described in subjects with severe disease. We studied heart rate variability (HRV) in COPD patients at rest and during the 6-minute Walk Test (6mWT) and the association with lung function impairment taking into account systemic inflammation. Thirty outpatients with stable COPD underwent lung function measurements, blood gas analysis, ECG Holter and transcutaneous pulse oximetry during 6mWT and then they were classified by BODE index. Also C-reactive protein (CRP) was measured. At rest, we observed a significant reduction of HRV for increasing BODE index. During the 6mWT, HRV tended to decrease in BODE 1 subjects whereas an increase was observed in BODE 2 and BODE 3-4 subjects. Subjects with elevated CRP values had a significant reduction in Standard Deviation of all normal RR intervals at rest (SDNN: p = 0.013), Total Power (TFA: p = 0.04) and Very Low Frequency band (VLF: p = 0.041). At rest, subjects with Inspiratory Capacity-to-Total Lung Capacity ratio (IC/TLC) < 36% had a significant reduced SDNN (p = 0.004), TFA (p = 0.001), VLF (p = 0.001), Low Frequency band (p = 0.007). During 6mWT, changes of HRV parameters were significantly related to airflow obstruction and static hyperinflation indices. At rest and during submaximal exercise, COPD patients with moderate and severe disease had an abnormal cardiac autonomic modulation which was related to both systemic inflammation and lung function impairment.

Autonomic dysfunction in patients with chronic obstructive pulmonary disease (COPD)

It has been recognized that chronic obstructive pulmonary disease (COPD) is a systemic disease which has been shown to negatively affect the cardiovascular and autonomic nerve system. The complexity of the physiologic basis by which autonomic dysfunction occurs in patients with COPD is considerable and the knowledge in this field remains elementary. The purpose of this review is to provide an overview of important potential mechanisms which might affect the autonomic nervous system in patients with COPD. This review aims to summarize the basic research in the field of autonomic dysfunction in patients with COPD. In COPD patients the activity of sympathetic nerves may be affected by recurrent hypoxemia, hypercapnia, increased intrathoracic pressure swings due to airway obstruction, increased respiratory effort, systemic inflammation and the use of betasympathomimetics. Furthermore, experimental findings suggest that autonomic dysfunction characterized by a predominance of sympathetic activity can significantly modulate further inflammatory reactions. The exact relationship between autonomic dysfunction and health status in COPD remains to be elucidated. Treatment aimed to restore the sympathovagal balance towards a reduction of resting sympathetic activity may modulate the inflammatory state, and possibly contributes to improved health status in COPD.

Heart Rate Variability, Homeostasis, and Brain Function

Measures of heart rate variability (HRV) are major indices of the sympathovagal balance in cardiovascular research. These measures are thought to reflect complex patterns of brain activation as well and HRV is now emerging as a descriptor thought to provide information on the nervous system organization of homeostatic responses in accordance with the situational requirements. Current models of integration equate HRV to the affective states as parallel outputs of the central autonomic network, with HRV reflecting its organization of affective, physiological, “cognitive,” and behavioral elements into a homeostatic response. Clinical application is in the study of patients with psychiatric disorders, traumatic brain injury, impaired emotion-specific processing, personality, and communication disorders. HRV responses to highly emotional sensory inputs have been identified in subjects in vegetative state and in healthy or brain injured subjects processing complex sensory stimuli. In this respect, HRV measurements can provide additional information on the brain functional setup in the severely brain damaged and would provide researchers with a suitable approach in the absence of conscious behavior or whenever complex experimental conditions and data collection are impracticable, as it is the case, for example, in intensive care units.

The effects of controlled breathing during pulmonary rehabilitation in patients with COPD

BACKGROUND

Conventional pulmonary rehabilitation programs improve exercise tolerance but have no effect on pulmonary function in patients with chronic obstructive pulmonary disease (COPD). The role of controlled breathing using respiratory biofeedback during rehabilitation of patients with COPD remains unclear.

OBJECTIVES

To compare the effects of a conventional 4-week pulmonary rehabilitation program with those of rehabilitation plus controlled breathing interventions.

METHODS

A randomized controlled trial was performed. Pulmonary function (FEV1), exercise capacity (6-min walking distance, 6 MWD), health-related quality of life (chronic respiratory questionnaire, CRQ) and cardiac autonomic function (rMSSD) were evaluated.

RESULTS

Forty COPD patients (mean±SD age 66.1±6.4, FEV1 45.9±17.4% predicted) were randomized to rehabilitation (n=20) or rehabilitation plus controlled breathing (n=20). There were no statistically significant differences between the two groups regarding the change in FEV1 (mean difference -0.8% predicted, 95% CI -4.4 to 2.9% predicted, p=0.33), 6 MWD (mean difference 12.2 m, 95% CI -37.4 to 12.2 m, p=0.16), CRQ (mean difference in total score 0.2, 95% CI -0.1 to 0.4, p=0.11) and rMSSD (mean difference 2.2 ms, 95% CI -20.8 to 25.1 ms, p=0.51).

CONCLUSIONS

In patients with COPD undergoing a pulmonary rehabilitation program, controlled breathing using respiratory biofeedback has no effect on exercise capacity, pulmonary function, quality of life or cardiac autonomic function.

Influence of long-term oxygen therapy on cardiac acceleration and deceleration capacity in hypoxic patients with chronic obstructive pulmonary disease

BACKGROUND

There is increasing interest in cardiovascular co-morbidities of chronic obstructive pulmonary disease (COPD). Heart rate turbulence (HRT) and phase-rectified signal averaging (PRSA) techniques quantify the heart's acceleration/deceleration capacities. We postulated that these methods can help assess the integrity of cardiac control in hypoxic COPD.

METHODS

Eight hypoxic stable COPD patients, nine healthy age-matched older adults and eight healthy young adults underwent ECG monitoring for 24 h. Patients with COPD were also monitored following 4 weeks of standardized oxygen therapy. HRT measures [turbulence onset (TO), turbulence slope (TS)] and PRSA-derived acceleration/deceleration (AC, DC) indices were quantified within 6-h blocks to assess circadian variation.

RESULTS

There were between-group differences for variables TS, DC and AC (P<0·0005, η(2) = 0·54-0·65), attributable solely to differences between healthy young and COPD subjects. Only HR (P<0·0005) and DC index (P = 0·008) showed circadian variation. A significant interaction 'trend' effect for HR (F(9,87) = 2·52, P = 0·015, η(2) = 0·21) reflected the strong influence of COPD on HR circadian variation (afternoon and night values being different to those in healthy subjects).

CONCLUSIONS

As expected, heart rate dynamics were substantially diminished in older (healthy and COPD) groups compared with healthy young controls. Patients with COPD showed similar heart rate dynamics compared with age-matched controls, both before and after hypoxia correction. However, there was a suggestion of diminished DC in COPD compared with age-matched controls (P = 0·059) that was absent following oxygen therapy. TS, DC and AC indices were altered by similar degrees in older subjects, apparently indicating equivalent tonic dysfunction of sympathetic/parasympathetic systems with ageing.

Interval hypoxic training improves autonomic cardiovascular and respiratory control in patients with mild chronic obstructive pulmonary disease

OBJECTIVES

Chronic obstructive pulmonary disease (COPD) is associated with cardiac autonomic nervous system dysregulation. This study evaluates the effects of interval hypoxic training on cardiovascular and respiratory control in patients with mild COPD.

METHODS

In 18 eucapnic normoxic mild COPD patients (age 51.7 +/- 2.4 years, mean +/- SEM), randomly assigned to either training or placebo group, and 14 age-matched healthy controls (47.7 +/- 2.8 years), we monitored end-tidal carbon dioxide, airway flow, arterial oxygen saturation, electrocardiogram, and continuous noninvasive blood pressure at rest, during progressive hypercapnic hyperoxia and isocapnic hypoxia to compare baroreflex sensitivity to hypoxia and hypercapnia before and after 3 weeks of hypoxic training. In double-blind fashion, both groups received 15 sessions of passive intermittent hypoxia (training group) or normoxia (placebo group). For the hypoxia group, each session consisted of three to five hypoxic (15-12% oxygen) periods (3-5 min) with 3-min normoxic intervals. The placebo group inhaled normoxic air.

RESULTS

Before training, COPD patients showed depressed baroreflex sensitivity, as compared with healthy individuals, without evident chemoreflex abnormalities. After training, in contrast to placebo group, the training group showed increased (P < 0.05) baroreflex sensitivity up to normal levels and selectively increased hypercapnic ventilatory response (P < 0.05), without changes in hypoxic ventilatory response.

CONCLUSION

Eucapnic normoxic mild COPD patients already showed signs of cardiovascular autonomic abnormalities at baseline, which normalized with hypoxic training. If confirmed in more severe patients, interval hypoxic training may be a therapeutic strategy to rebalance early autonomic dysfunction in COPD patients.

The relationship between dyspnea and blood pressure in chronic obstructive pulmonary disease

BACKGROUND AND RESEARCH OBJECTIVE

Although dyspnea is a frequently encountered clinical symptom, precise clinical evaluation of this sensation remains illusive. Dyspnea has been difficult to evaluate empirically, as severity of mechanical pulmonary impairment does not appear to correlate with subjectively reported levels of dyspnea. The purpose of this study was to describe changes in dyspnea and blood pressure with the use of an incentive spirometry and to examine the relationship of such changes in patients with chronic obstructive pulmonary disease.

SUBJECTS AND METHODS

A convenience sample of 60 adults diagnosed with chronic obstructive pulmonary disease was recruited from ambulatory outpatient clinics at a large Veterans hospital. A quantitative single-group, within-subjects repeated-measure design was used to investigate the relationship between the variables following incentive spirometry. Dyspnea levels were recorded with the visual analog scale and arterial blood pressures (beat-to-beat systolic, mean, and diastolic) were continuously recorded with tonometry.

RESULTS AND CONCLUSIONS

The first 4 periods following use of the incentive spirometer were found to have statistically significant increases from dyspnea baseline scores (F = 77.4, P < .001). The baseline of each of the arterial blood pressure measurements, systolic, mean, and diastolic, were found to have significant differences with all of the 6 postintervention time points (systolic F = 8.0, P < .001; mean F = 7.1, P < .001; diastolic F = 7.2, P < .001). The changes in dyspnea scores and blood pressure measurements were found to have significant inverse correlations at the immediate postintervention time point (r = -0.32 to -0.35, P < .01). Results provide evidence of an inverse relationship between dyspnea and blood pressure patterns and may indicate significant clinical associations to add to the body of knowledge about the symptom of dyspnea.

Effects of Nocturnal Noninvasive Mechanical Ventilation on Heart Rate Variability of Patients With Advanced COPD

BACKGROUND

Cardiovascular comorbidities have a negative impact on the health status and prognosis of patients with COPD. We determined whether nocturnal noninvasive (positive) mechanical ventilation (NIMV) can improve heart rate variability (HRV), decrease circulating natriuretic peptide levels, and improve functional performance of patients with very advanced COPD.

METHODS

A randomized, double-blind, parallel controlled trial was conducted in 23 participants with stable but advanced COPD. Participants received standard medical therapy plus nocturnal NIMV or standard medical therapy plus sham NIMV for 3 months.

RESULTS

After 3 months of NIMV therapy, the 24-h triangular interpolation of N-N intervals increased from 322 to 473 ms (p = 0.034), the 24-h HRV index (HRVI) increased from 21.8 to 29.9 ms (p = 0.035), nocturnal HRVI increased from 6.1 to 8.0 ms (p = 0.026), and the SD of the average N-N interval increased from 37 to 41 ms (p = 0.020). None of these indexes changed significantly in the control group. Additionally, compared with the control group, the pro-atrial natriuretic peptide levels declined significantly in the NIMV group (p = 0.013).

CONCLUSIONS

NIMV applied nocturnally over 3 months may improve HRV, reduce circulating natriuretic peptide levels, and enhance the functional performance of patients with advanced but stable COPD. While not definitive due to small sample size, these data suggest that nocturnal NIMV may reduce the impact of cardiac comorbidities in COPD patients.

The relationship between ambient air pollution and heart rate variability differs for individuals with heart and pulmonary disease

Associations between concentrations of ambient fine particles [particulate matter < 2.5 microm aerodynamic diameter (PM2.5)] and heart rate variability (HRV) have differed by study population. We examined the effects of ambient pollution on HRV for 18 individuals with chronic obstructive pulmonary disease (COPD) and 12 individuals with recent myocardial infarction (MI) living in Atlanta, Georgia. HRV, baseline pulmonary function, and medication data were collected for each participant on 7 days in fall 1999 and/or spring 2000. Hourly ambient pollution concentrations were obtained from monitoring sites in Atlanta. The association between ambient pollution and HRV was examined using linear mixed-effect models. Ambient pollution had opposing effects on HRV in our COPD and MI participants, resulting in no significant effect of ambient pollution on HRV in the entire population for 1-, 4-, or 24-hr moving averages. For individuals with COPD, interquartile range (IQR) increases in 4-hr ambient PM2.5 (11.65 microg/m3)) and nitrogen dioxide (11.97 ppb) were associated with 8.3% [95% confidence interval (CI), 1.7-15.3%] and 7.7% (95% CI, 0.1-15.9%) increase in the SD of normal R-R intervals (SDNN), respectively. For individuals with MI, IQR increases in 4-hr PM2.5 (8.54 microg/m3) and NO2 (9.25 ppb) were associated with a nonsignificant 2.9% (95% CI, -7.8 to 2.3) and significant 12.1 (95% CI, -19.5 to -4.0) decrease in SDNN. Beta-blocker and bronchodilator intake and baseline forced expiratory volume in 1 sec modified the PM-SDNN association significantly, with effects consistent with those by disease group. Results indicate heterogeneity in the autonomic response to air pollution due to differences in baseline health, with significant associations for ambient NO2 suggesting an important role for traffic-related pollution.

Spontaneous baroreflex cardiac sensitivity in end-stage liver disease: effect of liver transplantation

BACKGROUND AND OBJECTIVE

End-stage liver disease is associated with an imbalance in the autonomic nervous system. The purpose of this study was to estimate the effect of liver transplantation on this imbalance.

METHOD

The study involved 10 patients undergoing liver transplantation and 9 patients without liver impairment undergoing liver surgery. The spontaneous baroreflex sensitivity was measured before and 1 month after surgery for the liver surgery group; before and 1, 3, 6, 12 and 18 months after orthotopic liver transplantation.

RESULTS

The spontaneous baroreflex slope of patients with end-stage liver disease was decreased before liver transplantation compared to the liver surgery group (3.9 +/- 2.5 ms mmHg(-1) vs. 9.9 +/- 5.0 ms mmHg(-1), P = 0.002). The mean slope was significantly increased at 12 and 18 months compared to the pre-transplantation value (3.9 +/- 2.5 ms mmHg(-1) vs. 8.1 +/- 6.6 ms mmHg(-1) and 7.4 +/- 4.8 ms mmHg(-1), respectively; P = 0.042). Nevertheless, further analysis of individual data showed that only four patients exhibited a marked increase in their baroreflex slope 12 months after the liver transplantation whereas it remained decreased in the six others.

CONCLUSIONS

These results confirm that the baroreflex sensitivity is depressed in end-stage liver disease in line with an autonomic nervous system imbalance. The liver transplantation reverses this disturbance only in some patients.

Increased sympathetic and decreased parasympathetic cardiovascular modulation in normal humans with acute sleep deprivation

Cardiovascular autonomic modulation during 36 h of total sleep deprivation (SD) was assessed in 18 normal subjects (16 men, 2 women, 26.0 +/- 4.6 yr old). ECG and continuous blood pressure (BP) from radial artery tonometry were obtained at 2100 on the first study night (baseline) and every subsequent 12 h of SD. Each measurement period included resting supine, seated, and seated performing computerized tasks and measured vigilance and executive function. Subjects were not supine in the periods between measurements. Spectral analysis of heart rate variability (HRV) and BP variability (BPV) was computed for cardiac parasympathetic modulation [high-frequency power (HF)], sympathetic modulation [low-frequency power (LF)], sympathovagal balance (LF/HF power of R-R variability), and BPV sympathetic modulation (at LF). All spectral data were expressed in normalized units [(total power of the components/total power-very LF) x 100]. Spontaneous baroreflex sensitivity (BRS), based on systolic BP and pulse interval powers, was also measured. Supine and sitting, BPV LF was significantly increased from baseline at 12, 24, and 36 h of SD. Sitting, HRV LF was increased at 12 and 24 h of SD, HRV HF was decreased at 12 h SD, and HRV LF/HF power of R-R variability was increased at 12 h of SD. BRS was decreased at 24 h of SD supine and seated. During the simple reaction time task (vigilance testing), the significantly increased sympathetic and decreased parasympathetic cardiac modulation and BRS extended through 36 h of SD. In summary, acute SD was associated with increased sympathetic and decreased parasympathetic cardiovascular modulation and decreased BRS, most consistently in the seated position and during simple reaction-time testing.

The effect of ventilation on spectral analysis of heart rate and blood pressure variability during exercise

Heart rate variability (HRV) and systolic blood pressure variability (BPV) during incremental exercise at 50, 75, and 100% of previously determined ventilatory threshold (VT) were compared to that of resting controlled breathing (CB) in 12 healthy subjects. CB was matched with exercise-associated respiratory rate, tidal volume, and end-tidal CO(2) for all stages of exercise. Power in the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, >0.15-0.4 Hz) for HRV and BPV were calculated, using time-frequency domain analysis, from beat-to-beat ECG and non-invasive radial artery blood pressure, respectively. During CB absolute and normalized power in the LF and HF of HRV and BPV were not significantly changed from baseline to maximal breathing. Conversely, during exercise HRV, LF and HF power significantly decreased from baseline to 100% VT while BPV, LF and HF power significantly increased for the same period. These findings suggest that the increases in ventilation associated with incremental exercise do not significantly affect spectral analysis of cardiovascular autonomic modulation in healthy subjects.