Slow breathing reduces sympathoexcitation in COPD - Raupach et al. (2008)
Key Points
COPD patients suffer from greater sympathetic activity than healthy controls
Slow breathing reduces excess sympathetic activity in COPD patients
Slow breathing improves autonomic function in COPD patients
The Breathing Diabetic Summary
Chronic obstructive pulmonary disease (COPD) patients suffer from similar complications that diabetics do. For example, they have greater activation of the sympathetic nervous system and reduced baroreflex sensitivity. We know from previous studies that slow breathing positively impacts both of these parameters (for example, this one). Therefore, the goal of this study was to see if slow breathing could reduce sympathetic nerve activity while simultaneously improving baroreflex sensitivity in patients with COPD.
They studied 15 patients with non-hypoxic COPD and 15 age-matched healthy controls. Participants laid down at a 30 degree angle and breathed spontaneously for 20 minutes to acquire baseline measurements. Then, the subjects were instructed to breathe at 15 breaths/min for 4 minutes, followed by 4 minutes of breathing at 6 breaths/min (3 sec inhale, 7 sec exhale). The key parameters they measured during the experiment were muscle sympathetic nerve activity (MSNA) and baroreflex sensitivity (BRS; a measure of autonomic function).
Baseline MSNA (sympathetic activity) was significantly higher in the COPD patients than controls. When breathing was reduced to 6 breaths/min, MSNA decreased significantly in the COPD patients, but not in the controls. This implies that slow breathing doesn’t just reduce sympathetic nerve activity in general: it reduces excess sympathetic activity to bring the body back to its normal physiological state. Lastly, both the controls and the COPD patients showed a significant increase in BRS (autonomic function) when breathing at 6 breaths/min, something we have seen in several other studies.
Overall, this study found that slow breathing significantly reduces sympathetic nerve activity in COPD patients. Moreover, they found that BRS was significantly increased when breathing was reduced to 6 breaths/min. A concise quote from their paper summarizes it nicely:
“In summary, patients with chronic obstructive pulmonary disease showed sympathetic excitation and depression of the baroreflex.Slow breathing counteracted these changes.”
Abstract from Paper
Neurohumoral activation has been shown to be present in hypoxic patients with chronic obstructive pulmonary disease (COPD). The aims of the present study were to investigate whether there is sympathetic activation in COPD patients in the absence of hypoxia and whether slow breathing has an impact on sympathoexcitation and baroreflex sensitivity.
Efferent muscle sympathetic nerve activity, blood pressure, cardiac frequency and respiratory movements were continuously measured in 15 COPD patients and 15 healthy control subjects. Baroreflex sensitivity was analysed by autoregressive spectral analysis and the alpha-angle method.
At baseline, sympathetic nerve activity was significantly elevated in COPD patients and baroreflex sensitivity was decreased (5.0 +/- 0.6 versus 8.9 +/- 0.8 ms mmHg-1). Breathing at a rate of 6 breaths min-1 caused sympathetic activity to drop significantly in COPD patients (from 61.3 +/- 4.6 to 53.0 +/- 4.3 bursts per 100 heartbeats) but not in control subjects (39.2 +/- 3.2 versus 37.5 +/- 3.3 bursts per 100 heartbeats). In both groups, slow breathing significantly enhanced baroreflex sensitivity.
In conclusion, sympathovagal imbalance is present in normoxic chronic obstructive pulmonary disease patients. The possibility of modifying these changes by slow breathing may help to better understand and influence this systemic disease.
Journal Reference:
T. Raupach, F. Bahr, P. Herrmann, L. Luethje, K. Heusser, G. Hasenfuß, L. Bernardi+,1 and S. Andreas (2008), Slow breathing reduces sympathoexcitation in COPD, European Respiratory Journal, 32 (2), 387 – 392, DOI: 10.1183/09031936.00109607.