Cough reflex sensitivity in adolescents with diabetic autonomic neuropathy.

OBJECTIVE: Diabetic autonomic neuropathy (DAN) is one of the chronic complications of diabetes mellitus which can involve one or more organ systems. DAN without apparent symptoms is more often in childhood and adolescence. While heart rate variability (HRV) and Ewing's battery of cardiovascular tests are regarded as a gold standard for the diagnosis of DAN, the examination of cough reflex sensitivity (CRS) is another possibility. The aim of this study was to compare HRV and CRS in children with diabetes mellitus. MATERIAL AND METHODS: Sixty one patients (37 girls, 24 boys) aged 15-19 suffering from diabetes mellitus type 1 completed the study. Based on HRV, patients were divided into 2 groups - with DAN (n=25) and without DAN (n=32), 4 patients were excluded because of ambiguous results. CRS was studied in each patient by inhalation of gradually increasing concentration of capsaicin. RESULTS: Subjects with DAN required a significantly higher concentration of capsaicin needed to evoke 2 coughs (median 625 micromol/l, IQR 68.4-625.0 micromol/l vs. median 29.3 micromol/l, IQR 9.8-156.3 micromol/l, P<0.001) and 5 coughs (median 2500.0 micromol/l, IQR 1250.0-2500.0 micromol/l vs. median 312.5 micromol/l, IQR 117.2-625.0 micromol/l, P<0.001) compared with those without DAN. Moreover, a strong negative correlation between HRV and CRS was established. CONCLUSION: Diabetes mellitus lowers the cough response. Cough reflex sensitivity appears to be another sensitive method for the evaluation of DAN in diabetes.

Cardio-respiratory interaction and autonomic dysfunction in obesity.

We aimed to test whether the evaluation of the cardio-respiratory interaction using the analysis of heart rate and blood pressure variabilities and respiratory maneuvers can reveal cardiovagal dysfunction in obese adolescents 12-18 years old. The spectral power in high frequency band of the heart rate variability (HRV) reflecting respiratory sinus arrhythmia was used as an index of the cardiac vagal control, and the spectral power in high frequency band of the blood pressure variability (BPV) as an indicator of mechanical effects of respiration. The deep breathing test and Valsalva maneuver were applied. The obese group had a reduction in spectral power in high frequency band of the HRV. Differences in high frequency band spectral power of the BPV between the obese and control groups were not found. The finding of lower respiratory sinus arrhythmia, indicating a cardiovagal dysfunction in obese adolescents, can provide important diagnostic information about early subclinical autonomic dysfunction in obesity.

The influence of autonomic neuropathy on cough reflex sensitivity in children with diabetes mellitus type 1.

Diabetic autonomic neuropathy (DAN) is manifested by dysfunction of one or more organ systems. Its subclinical form (sDAN) can be recognized with the use of noninvasive cardiovascular reflex tests. As the cough reflex is mediated via autonomic nervous system, there is a reason to suppose that it can also be changed due to presence of sDAN. The aim of the present study was to assess cough reflex sensitivity (CRS) in diabetic children with and without sDAN. A CRS test was performed in 35 children suffering from diabetes mellitus type 1 and the results were compared with those from age-matched 27 healthy children. Cough was induced by inhalation of capsaicin aerosol in doubling concentrations (0.61-1250 micromol/l) for 400 ms each. CRS was defined as the lowest capsaicin concentration that evoked 2 or more coughs (C2 parameter) and 5 or more coughs (C5 parameter). We found that CRS in the whole group of diabetic children was not significantly different from that in healthy children [diabetic children--C2: 75.1 micromol/l (95% CI: 42.0-134.2 micromol/l)] vs. healthy children--C2: 72.4 micromol/l (95% CI: 75.7-644.8 micromol/l)]. However, a significant decrease (P=0.005) in CRS was found in diabetic children with sDAN [n=12; C2: 221.0 micromol/l (95% CI: 75.7-644.8 micromol/l)] compared with diabetic children without sDAN [(n=23; C2: 42.7 micromol/l (95% CI: 23.1-79.0 micromol/l)]. We conclude that testing cough reflex sensitivity might be a way to establish the presence of diabetic neuropathy.