Slow breathing reduces sympathoexcitation in chronic obstructive pulmonary disease

¹ Dept. of Cardiology and Pneumology, Georg-August University Goettingen, Germany
² Dept. of Anaesthesiology II and Intensive Care, Georg-August University Goettingen, Germany
³ Franz-Volhard-Clinical Research Center, Medical University Charité, Berlin, Germany
⁴ Dept. of Internal Medicine, University of Pavia and IRCCS S Matteo, Pavia, Italy
⁵ Dept. of Cardiology and Pneumology, Georg-August University Goettingen, Germany; and Specialist Lung Clinic Immenhausen, Germany

^* To whom correspondence should be addressed. E-mail: sandreas{at}lungenfachklinik-immenhausen.de.

	Abstract

Neurohumoral activation has been shown to be present in hypoxic patients with chronic obstructive pulmonary disease (COPD). The aim of this study was to investigate whether there is sympathetic activation in COPD patients in the absence of hypoxia, and whether slow breathing impacts on sympathoexcitation and baroreflex sensitivity.

Efferent muscle sympathetic nerve activity, blood pressure, heart rate and respiratory movements were continuously measured in 15 patients and 15 healthy control subjects. Baroreflex sensitivity was analyzed by autoregressive spectral analysis and the alpha angle method.

At baseline, sympathetic nerve activity was significantly elevated in patients, and baroreflex sensitivity was decreased (5.0±0.6 ms·mmHg^-1 vs. 8.9±0.8 ms·mmHg^-1, p=0.004). Breathing at a rate of 6·min^-1 caused sympathetic activity to drop significantly in patients (from 61.3±4.6 bursts/100 heartbeats to 53.0±4.3 bursts/100 heartbeats; p<0.001), but not in control subjects (39.2±3.2 bursts/100 heartbeats vs. 37.5±3.3 bursts/100 heartbeats; p=0.308). In both groups, slow breathing significantly enhanced baroreflex sensitivity.

In conclusion, sympathovagal imbalance is present in normoxic COPD patients. The possibility of modifying these changes by slow breathing may help to better understand and influence this systemic disease.