| Abstract [eng] |
Cardiovascular autonomic neuropathy (CAN) is one of the least recognised and understood complications of diabetes mellitus (DM). It is important to detect CAN at an early stage of development to prevent damage of the autonomic nervous system (ANS). In healthy individuals, the heart rate is related to the respiratory cycle: the heart rate increases during inhalation and decreases during exhalation. This phenomenon, known as respiratory sinus arrhythmia (RSA), and is often interpreted as a cardiac vagal tone index. This phenomenon monitoring can be used to assess the parasympathetic nervous system (PNS), which is the most damaged part of ANS for DM patients, and may indicate CAN. D. J. Ewing’s CART tests have been used to investigate autonomic functions and to diagnose CAN. However, these tests are time-consuming, and because of irregular diagnostic, most of the cases CAN are diagnosed after symptoms occur. There is a high demand of methodology for simple, fast, and regular screening of CD patients for possible development of CAN. To evaluate the impact of ANS stimulation, physiological database was analysed by using the analysis of heart rate variability (HRV) and RSA. The database used in the study consists of three homogeneous groups: DM patients without diagnosed CAN, DM patients with diagnosed CAN, and healthy subjects. HRV parameters used in the analysis: SDNN, RMSSD, pNN50, entropy, spectral analysis of three frequency bands (VLF, LF, and HF), and LF/HF ratio. Three methods of RSA analysis were used: 1) R–R interval and respiratory signal relationship methods, assessing the existence of RSA in the respiratory cycle; 2) Porges–Bohrer method, which derives an estimate from the R–R signal; and 3) R–R minimum-maximum difference in the respiratory cycle, which allows to determine the amplitude of the RSA. Statistical evaluation of the calculated parameters was performed. Values of p and effect size were calculated among the groups. Significant differences were observed only between DM patients’ group and DM patients with CAN group. A deep breath and static load tests were found to be best for ANS stimulation. |
