Spectral Analysis of Heart Rate Variability during Resting and Controlled Breathing in Chronic Obstructive Pulmonary Disease patients attending Tertiary Care Centre

INTRODUCTION: COPD is a common treatable and preventable disease characterized by airflow limitation and persistent respiratory symptoms that is due to airway or alveolar abnormalities usually caused by significant exposure to noxious gases or particles. According to WHO’s report, 65 million people have moderate to severe chronic obstructive pulmonary disease (COPD). Earlier, COPD was more common in men, but because of increased tobacco use among women in high-income countries and the higher risk of exposure to indoor air pollution (such as biomass fuel used for cooking and heating) in low-income countries, the disease now affects men and women almost equally. The coexistence of expiratory flow limitation and loss of elastic recoil of the lung causes changes in the breathing pattern and in lung volume. Accordingly, a series of hemodynamic adjustments occur, especially in the autonomic control of heart rate to maintain homeostasis. In COPD patients, the autonomic nervous system may be affected by recurrent hypoxemia, hypercapnia, airway obstruction, increased respiratory effort, systemic inflammation and the use of beta sympathomimetics. AIM AND OBJECTIVE: 1. To evaluate the autonomic dysfunction in patients with COPD. 2. To determine whether pattern of HR variability in this population is different from normal population. 3. To analyse the spectral disturbances during resting and controlled breathing. METHODOLOGY: The study was conducted in the Department of Physiology, Chengalpattu Medical College & Hospital, Chengalpattu. The study group consists of 35 COPD patients as cases and 35 healthy volunteers (age and gender matched) as controls. Study was conducted after getting approval from the Institutional Ethical Committee. Subject was explained about the details of the study and informed written consent was obtained. Detailed history and clinical examination were carried out to rule out any cardiac or neural disorders. Subjects were asked to avoid coffee, nicotine and alcohol 24 hours prior to test. Drugs like aminophylline, steroids & beta 2 agonists to be stopped before 24 hours and asthalin inhalers 4 hrs before the procedure after consultation with physician. The patients were subjected to study in the morning at least 2 hours after a light breakfast, in a room with constant temperature and humidity. Subject was advised to void urine before recording, instructed to relax in supine position. ECG electrodes & respiratory transducer was attached to the subject to the subject & connected to HRV acquisition hardware (Variowin). Two periods make up the study protocol, after adaptation to the environment: (1) rest period, subject quietly recumbent; (2) controlled breathing, 15 cycles/min, to enhance the vagal-mediated respiratory component of HRV. RESULTS: The frequency domain parameter LF nu is 0.55 ± 0.22 was little high in cases, when compared to 0.52 ± 0.09 of controls, with no significance. HF nu of 0.44 ± 0.22 in COPD patients was less when compared to 0.47 ± 0.09 in controls, with no statistical significance. LF/HF ratio of 1.89 ± 1.59 was high in cases, compared to 1.17 ± 0.44 in controls, with a significant p value of 0.013*. RMSSD was 32.52 ± 25.01 in COPD patients, low when compared to 55.24 ± 17.48 in control showing a statistical significance. SDNN was low 33.13 ± 18.27 in COPD patients, when compared to 55.67 ± 15.40 in controls, with a statistically significant p value of 0.0001*. LF nu changes little from 0.55 ± 0.22 to 0.54 ± 0.20, showing a decrease during controlled breathing. HF nu was 0.45 ± 0.22, increased only a little from 0.44 ± 0.20, during the CB session. RMSSD also showed a little rise from 32.52 ± 25.01 to 36.92 ± 26.43 during controlled breathing. SDNN changes from 33.13 ± 18.27 to 40.06 ± 23.32, showing an increase during controlled breathing. CONCLUSION: Decreased heart rate variability in COPD patients shows the presence of ANS dysfunction with sympathetic hyperactivity. After CB, though there is a slight rise in parasympathetic action and an increase in variability in heart rate, they are not statistically significant. So, it is inconclusive to decide on the effect of CB in this study