Objective. To determine peculiarities of the vital functions control in patients with obstructive sleep apnea syndrome (OSAS) of different severities while monitoring the heart rate variability parameters for choosing a personalized complex of treatment measures according to the functional state of every specific patient’s organism.

Materials and methods. The heart rate variability characteristics had been registered using the Intecard and Briz-HR (Intecard EMS, Belarus) hard- and software in 29 men and 7 women aged 26—60 with verified obstructive sleep apnea syndrome of various severities for 5 minutes in the daytime when they were in the waking state. The geometrical and frequency methods were studied. The data obtained were processed statistically (two-sample criterion of Kolmogorov—Smirnov and Spearman’s rank correlation). The value p<0.05 was accepted as the statistically reliable limit.

Results. Statistically significant (p<0.05) change of the geometrical method parameters of the heart rate variability was found in the OSAS patients. The total capacity of the autonomous nervous system decreased up to 3 times, the parasympathetic contour capacity — up to 2 times as well as activity of the sympathoadrenal part increased up to 2 times, and the stress-index — up to 3 times along with the disease severity increase. The spectral analysis revealed statistically significant by 50—75% (p<0.05) and by 60—75% (p<0.05) lowering of the parasympathetic and sympathetic absolute values, respectively.

Conclusion. With the OSAS severity increasing, a statistically significant decrease of the parasympathetic and sympathetic circuits absolute values was identified. A trend to the sympathovagal balance shifting in the direction of sympathicotonia was registered as the OSAS was progressing. It is advisable to control the therapeutic interventions efficacy in such patients using the heart rate variability parameters.