No effect of naloxone on ventilatory response to progressive hypercapnia in IDDM patients.

The ventilatory response to hyperoxic progressive hypercapnia was examined by comparing 3 test groups: 7 diabetic patients with AN, 8 diabetic patients without AN, and 8 normal control subjects. In each group, a significant linear correlation was found between PaCO2 and VE. The slopes of the regression curves relating PaCO2 to VE were significantly steeper in the healthy control subjects and diabetic patients without AN than in those with AN (P < 0.01). We conclude that the ventilatory response to progressive hypercapnia is reduced in diabetic patients with AN. By analyzing the power spectrum and the amplitude behavior of the diaphragmatic EMG (calculated from the fc and RMS, respectively), we could exclude a disturbance of neural descending pathways and respiratory muscle dysfunction as possible causal mechanisms for the impaired ventilatory response to increasing CO2. By using lung function analysis, causal factors such as alterations in respiratory system mechanics also could be excluded. As diabetes is known to affect the endogenous opioid system, which, in turn, affects the ventilatory response to CO2, naloxone, as a specific opioid antagonist, was administered in all 3 test groups. Naloxone produced a significant increase of ventilatory response to hypercapnia in the healthy control subjects (P < 0.01), but produced no effect in either of the diabetic groups.(ABSTRACT TRUNCATED AT 250 WORDS)