AUTONOMIC NERVE DYSFUNCTION IN COPD AS ASSESSED BY THE ACETYLCHOLINE SWEAT-SPOT TEST

Patients with hypoxic chronic obstructive pulmonary disease (COPD) hav e evidence of a subclinical parasympathetic autonomic neuropathy, with apparent preservation of sympathetic function. However, these cardiov ascular-respiratory tests might have been biased by concomitant chest disease, the acetylcholine sweat-spot test avoids this bias. This swea t-spot test assesses sympathetic nerve function, it relies upon the fa ct that denervated sweat glands do not produce sweat. 35 patients with hypoxaemic COPD and seven age matched normal subjects were studied. F ollowing intradermal injection of 0.1 of 1 % acetylcholine into the do rsum of the feet, the number of sweatglands able to respond in a given surface area was recorded. Cardiovascular autonomic nerve function, a rterial oxygen and carbon dioxide tensions, lung function and cigarett e consumption were also recorded. The acetylcholine sweat-spot test wa s highly repeatable in eight COPD patients, no person with normal or f rankly abnormal function being wrongly assigned. The age matched contr ol subjects had normal acetylcholine sweat-spot scores and cardiovascu lar autonomic tests. The acetylcholine sweat-spot test was abnormal in 24 patients, borderline in 8 and normal in 3 patients. The abnormal s weat-spot test group had significant worse FEV1, arterial blood gases and autonomic function. The acetylcholine sweat-spot score correlated with the severity of arterial hypoxaemia (r=0.78, p<0.001) and with th e parasympathetic cardiovascular tests (r=0.80, p<0.001). In conclusio n, patients with hypoxaemic COPD have a parasympathetic cardiovascular and a peripheral sympathetic autonomic neuropathy. The acetylcholine sweat-spot test is repeatable, easy to perform and a sensitive indicat or for autonomic dysfunction ii breathless individuals with COPD.