Diminished bronchial reactivity to cold air in diabetic patients with autonomic neuropathy.

To investigate the role of neural pathways in the nonasthmatic response to eucapnic hyperventilation with below freezing air five diabetic patients with severe symptomatic autonomic neuropathy were studied. Their responses were compared with those shown by five diabetic patients without autonomic neuropathy and five non-diabetic controls. After bronchial provocation testing with cold air the diabetic patients with autonomic neuropathy did not show a significant fall in specific airways conductance (mean (SE) maximum percentage fall 2.0 (3)%), whereas conductance fell in the diabetic patients without neuropathy by 30.8 (2.0)% (p less than 0.001) and in the non-diabetic controls by 22.7 (4.6)% (p less than 0.02). In subjects who do not have asthma the bronchial response to cold air is mediated largely via neural mechanisms.