Chest
Volume 106, Issue 5, November 1994, Pages 1432-1437
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Clinical Investigations: COPD
Decreased Heart Rate Variability in Patients With Chronic Obstructive Pulmonary Disease

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To evaluate possible autonomic nervous system (ANS) dysfunction in patients with chronic obstructive pulmonary disease (COPD) in the absence of any hypoxic neuronal damage, we studied 31 patients with COPD patients aged 31 to 68 years (55 ± 10) and 32 age-matched healthy subjects (control). Respiratory function in the patients was as follows: FEV1=52 ± 8 percent; PaO2=71 ± 14 mm Hg; and PaCO2=40 ± 10 mm Hg. The ANS was assessed by heart rate variability (HRV) in the time domain (SD of mean RR interval) and frequency domain (autoregressive spectral analysis recognizing low [LF] and high [HF] frequency components, vagal and sympathetic related, respectively). Patients and controls were evaluated at rest and during vagal (controlled breathing [CB]) and sympathetic (passive head-up tilt) maneuvers. Patients with COPD showed a depressed global HRV (rest SD=34 ± 20 ms vs 45 ± 15 ms, p<0.05; tilt SD=28 ± 14 ms vs 38 ± 13, p<0.01) with a predominant respiratory drive (rest HF=44 ± 28 vs 28 ± 18, p<0.05; tilt HF 42 ± 28 vs 16 ± 12, p<0.01) as compared with normal subjects. In the control group, vagal and sympathetic responses were in opposite directions following a stimulus, whereas there was no significant HRV response in the COPD group. We conclude that patients with COPD have abnormalities of ANS function, with in particular a depressed HRV response to sympathetic and vagal stimuli.

ANS=autonomic nervous system; CB=controlled breathing; HF=high frequency; HRV=heart rate variability; LF=low frequency; nu=normalized unit

Section snippets

Aim of the Study

The aim of this study was to evaluate by HRV analysis the presence of autonomic dysfunction in patients with COPD and to determine whether the pattern of HR variability in this population is different from the normal population.

Study Population

Informed consent was obtained from 31 male inpatients with a history of COPD, as defined by the American Thoracic Society,18 and 32 aged-matched control subjects. The patients were between 31 and 68 years of age (mean=55 ± 10), normoxemic (mean PaO2=70.85 ± 13.93 mm Hg) and with a forced expiratory volume in 1 s (FEV1) of less then 65 percent of the predicted value (mean=52 ± 8.3 percent). Exclusion criteria were as follows: coronary artery disease; hypertension; encephalopathy; and diabetic

Results

Table 1 shows the mean values and SDs of measured and computed parameters at rest, during controlled breathing, and in passive head-up tilt.

In patients with COPD, the mean RR interval decreased after passive tilt (858 ± 127 ms vs 738 ± 130.76 ms), whereas there were no statistically significant changes during controlled breathing. Although the mean RR was slightly higher in the normal subjects during the whole test, this was not statistically significant. Significant differences between groups

Discussion

In this study, we have examined the differences in autonomic nervous control of heart rate in 31 patients with COPD compared with an age- and sex-matched control group under standardized conditions, to obtain an index of both static and dynamic neurovegetative balance, ie, at rest and during known autonomic stimuli.

The vagus nerve is known to modulate the rate of sinoatrial discharge. The possibility exists that an abnormality in the parasympathetic control of airway caliber may be reflected by

Conclusion

The complexity of the pulmonary effects of the autonomic nervous system is considerable, and our knowledge in this field remains elementary. Our results suggest that in patients with COPD, there is an imbalance in autonomic nervous system activity. This is apparently driven at rest by an increase in vagal activity and through the lack of responsiveness to sympathetic stimulation. This altered balance could contribute to the airways obstruction in COPD.

More studies are needed to increase our

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