Marked sympathetic activation in patients with chronic respiratory failure

The autonomic nervous system may be disturbed in chronic respiratory failur e. We tested the hypothesis that there is increased sympathetic activity in patients with chronic hypoxemia. Furthermore, we examined the effect of sh ort-term oxygen on muscle sympathetic nerve activity (MSNA) in these patien ts. We performed microneurography of the peroneal nerve in 11 patients with hypoxemia due to chronic obstructive pulmonary disease (COPD, n = 6) or lu ng fibrosis (n = 5) and in 11 healthy subjects matched for age and sex. MSN A was measured during normal breathing in all subjects. In eight patients a nd in seven control subjects, MSNA was also measured during nasal oxygen (4 L/min). MSNA was higher in the patients with chronic respiratory failure c ompared with the healthy subjects during normal breathing (61 +/- 5 versus 34 +/- 2 bursts/min, mean +/- SEM; p = 0.0002, paired t test). During oxyge n administration, MSNA decreased from 63 +/- 6 to 56 +/- 6 bursts/min in th e patients (p = 0.0004, ANOVA); there was no change in sympathetic activity in the control subjects. For the first time, there is direct evidence of m arked sympathetic activation in patients with chronic respiratory failure. This is partly explained by arterial chemoreflex activation and may play an important role in the pathogenesis of the disease.