Preservation of the hypoxic drive to breathing in diabetic autonomic neuropathy.

1. Unexplained cardiorespiratory arrests have been reported in patients with diabetic autonomic neuropathy and these could be due to denervation of the carotid chemoreceptors. 2. We have studied the ventilatory response to transient hypoxia (Ve/Peto2) during exercise in 22 male diabetic patients, six with symptomatic and cardiovascular evidence to suggest diabetic autonomic neuropathy (DAN+) and 12 without these features (DAN-). 3. There was no difference in the ventilatory response to transient hypoxia between the different groups of diabetic patients (Ve/Peto2 in DAN+ patients = -0.9 +/- 0.2 litre min-1 kPa-1; Ve/Peto2 in DAN- patients = -1.2 +/- 0.6 litres min-1 kPa-1) even allowing for differences in the level of exercise achieved (CO2 production in DAN+ patients = 743 +/- 103 ml/min; CO2 production in DAN- patients = 800 +/- 144 ml/min). These results fell within our normal range for ventilatory response to transient hypoxia at this level of exercise. 4. The heart rate response to transient hypoxia varied within the groups but was significantly (P less than 0.05) less in the patients with established diabetic autonomic neuropathy. 5. We conclude that the peripheral chemoreceptors are intact in diabetic autonomic neuropathy and that other mechanisms must be implicated in the unexpected cardiorespiratory arrests seen in these patients.