essential hypertension; diabetes mellitus type-I; baroreflex sensitivity; spectral analysis

The aim of the study was to determine the relationship between the variability in systolic blood pressure (SBP) and RR-intervals (RRI) with respect to the baroreflex sensitivity (BRS) in adolescents with diabetes mellitus type-I (DM-I) and essential hypertension (EH). BP was recorded in 171 adolescents (130 healthy, 22 DM-I, 16 EH, 16-20 years) for 5-min (Finapres, metronome controlled breathing at a frequency of 0.33 Hz). The power spectra of SBP [mmHg2 /Hz] and RRI [ms2/Hz] were calculated. BRS was determined by crossspectral method. Adolescents were divided into 9 subgroups according to the RRI/SBP spectral power around the frequency of 0.1 Hz. The limits of power were estimated as percentiles (33.3% and 66.6%). DM-I has significantly higher SBP and RRI ariability but no changes in BRS in comparison to healthy; however, DM-I have in comparison with EH significantly higher BRS and RRI variability, but no significant changes in SBP variability. Significant changes in distribution of EH and DM-I in particular subgroups were found. Adolescents with DM-I are concentrated in area with high SBP and RRI variability which corresponds to the mean values of BRS. On the other hand, EH adolescents concentrate to the areas only with high SBP variability which corresponds to the low values of BRS.