Background: While autonomic neuropathy has been reported in chronically hypoxaemic patients of chronic obstructive pulmonary disease (COPD), whether it also occurs in patients with milder disease and in those without chronic hypoxaemia has not been explored.
Methodology: Lung function measurements including spirometry and transfer factor for carbon monoxide, mean pulmonary artery pressure estimation by color-doppler echocardiography and arterial blood gas analysis were carried out in 56 patients with COPD and 11 age-matched controls. Autonomic function was assessed by tests of cardiovascular reflexes and expressed as valsalva ratio, 30:15 ratio, IE difference and the blood pressure response to postural change.
Results: Among patients, majority of the test responses were in the abnormal or borderline range compared to more than 90% of test responses in the normal or borderline range among normals. Almost 50% of patients had definite neuropathy as compared to none in normals. Although, the autonomic neuropathy tended to be observed more often in patients with moderate and severe COPD, it was also found in a fair proportion of patients with mild COPD. Similarly, while it was more prevalent in patients with hypoxaemia, it was also found to occur in those without hypoxaemia. The responses to tests of autonomic function had weak relationships with FEV1% predicted and PaO2.
Conclusions: Cardiovascular autonomic neuropathy is common in COPD and is found even in early stages of the disease.