Cardiac Autonomic Function and Reactivity Tests in Physically Active Subjects with Moderately Severe COPD

Anxiety Is a Mediator between Heart Rate Variability and Quality of Life in Chronic Obstructive Pulmonary Disease

Autonomic nervous system (ANS) dysregulation is an important pathophysiological mechanism in patients with chronic obstructive pulmonary disease (COPD). Heart rate variability (HRV) is a common index for ANS, and HRV has been used to explore the association between ANS and clinical illnesses. This study aimed to explore the group differences in HRV, depression, anxiety, and quality of life between participants with COPD and healthy controls (HC group), and whether emotion plays a mediating role between HRV and quality of life in participants with COPD. A total of ninety-six participants with COPD and 59 participants in the HC group completed the Beck Depression Inventory-II (BDI-II), Beck Anxiety Inventory (BAI), and Saint George’s Respiratory Questionnaire (SGRQ). Assessment of spirometry pulmonary function and five minute lead II electrocardiography (ECG) were also performed under the resting baseline. The COPD group had higher depression scores (F = 4.10, p = 0.008), and a lower quality of life (F = 14.44, p < 0.001) and HRV indices (such as standard deviation of RR intervals (F = 5.49, p < 0.05) and low frequency (F = 3.03, p < 0.05)) compared to the HC group. Sympathetic activation was positively correlated with depression (r = 0.312, p < 0.01), anxiety (r = 0.420, p < 0.001), and poor quality of life (r = 0.467, p < 0.001) in the COPD group. After controlling for age and sex, anxiety (β = 0.585, p < 0.001) and sympathetic activation (β = 0.231, p < 0.05) positively predicted poor quality of life, and lung function (β = −0.251, p < 0.01) negatively predicted poor quality of life. Therefore, anxiety is a mediator between sympathetic activation and quality of life. Emotional and HRV screening should be applied to COPD patients in clinical practice, and emotional management or HRV biofeedback training can be used to improve anxiety and HRV for future studies.

Chronotropic Index and Acute Exacerbations of Chronic Obstructive Pulmonary Disease: A Secondary Analysis of BLOCK COPD

Rationale: The chronotropic index quantifies the proportion of the expected heart rate increase that is attained during exercise. The relationship between the chronotropic index and acute exacerbations of chronic obstructive pulmonary disease (AECOPDs) has not been evaluated. Objectives: To determine whether a higher chronotropic index during a 6-minute walk (CI-6MW) is associated with lower risk of AECOPD and whether the CI-6MW is a marker of susceptibility to adverse effects of metoprolol in chronic obstructive pulmonary disease (COPD). Methods: We analyzed data from the BLOCK COPD (Beta-Blockers for the Prevention of AECOPDs) trial. We used Cox proportional hazards models to investigate the relationship between the CI-6MW and the time to AECOPDs. We also tested for interactions between study group assignment (metoprolol vs. placebo) and the CI-6MW on the time to AECOPDs. Results: Four hundred seventy-seven participants with exacerbation-prone COPD (mean forced expiratory volume in 1 second, 41% of predicted) were included in this analysis. A higher CI-6MW was independently associated with a decreased risk of AECOPDs of any severity (adjusted hazard ratio per 0.1 increase in CI-6MW of 0.88; 95% confidence interval, 0.80-0.96) but was not independently associated with AECOPDs requiring hospitalization (adjusted hazard ratio, 0.94; 95% confidence interval, 0.81-1.05). There was a significant interaction by treatment assignment, and in a stratified analysis, the protective effects of a higher CI-6MW on AECOPDs were negated by metoprolol use. Conclusions: A higher CI-6MW is associated with a decreased risk of AECOPDs and may be an indicator of susceptibility to the adverse effects of metoprolol.

Cardiac Autonomic Control in Women with Rheumatoid Arthritis During the Glittre Activities of Daily Living Test

Background: Cardiovascular autonomic dysfunction is one of the most common complications in rheumatoid arthritis (RA), which can be assessed by heart rate variability (HRV) analysis. Because the autonomic nervous system plays an important role in orchestrating the cardiovascular response to stressors, assessing HRV during exercise is critical. The Glittre Activities of Daily Living test (GA-T) was recently proposed as a multitask field test that requires the performance of the upper and lower limbs, both of which are affected in individuals with RA. Objectives: This study was conducted to evaluate autonomic impairment by HRV in women with RA using the GA-T and to correlate these changes with physical functioning and muscle strength. Methods: This cross-sectional study enrolled 20 women (median [interquartile range]: age 55 [47.5 - 68.8] years) with RA (time since diagnosis: 15 [6.50 - 23.5] years) who underwent HRV assessment during GA-T. They also underwent physical functioning assessment through the Health Assessment Questionnaire Disability Index (HAQ-DI) and handgrip strength (HGS) and quadriceps strength (QS) measures. Results: The GA-T time exhibited significant correlations with the following HRV indices: root mean square of successive differences (RMSSD, rs = -0.451, P = 0.041), proportion of iRR differing by > 50 ms from previous intervals (pNN50, rs = -0.697, P = 0.0006), high frequency (HF, rs = -0.693, P = 0.0007), standard deviation of the points perpendicular to the line-of-identity (SD1, rs = -0.476, P = 0.034), and approximate entropy (ApEn, rs = 0.545, P = 0.013). In addition, the HAQ-DI exhibited significant correlations with the following HRV indices: pNN50 (rs = -0.467, P = 0.038) and HF (rs = -0.444, P = 0.049). We did not observe significant correlation between the HRV indices during the GA-T and the muscle strength measures (HGS and QS). Conclusions: In women with RA, the longer the required to perform the GA-T the worse their parasympathetic modulation, sympathetic-vagal imbalance, and complexity of the autonomic nervous system (i.e., increased index of ApEn) were. Physical functioning level was also related to vagal modulation.

Interaction between the respiratory system and cerebral blood flow regulation

This review summarizes the interaction between the regulatory system of respiration and cerebral vasculature. Some clinical reports provide evidence for the association between these two physiological regulatory systems. Physiologically, arterial carbon dioxide concentration is mainly regulated by two feedback control systems: respiration and cerebral blood flow. In other words, both of these systems are sensitive to the same mediator, i.e., carbon dioxide, at a set point. In addition, respiratory dysfunction alters various physiological factors that affect the cerebral vasculature. Therefore, it is physiologically plausible that these systems are closely linked. The regulation of arterial carbon dioxide concentration affected by respiration and cerebral blood flow may be a key factor for a rise in the risk of brain disease in the patients with respiratory dysfunction. For example, the management of respiratory disease (e.g., patients with chronic obstructive pulmonary disease) and the use of prophylactic therapy are essential to reduce the risk of stroke.