Typological Features of the Heart Rate Autonomic Regulation under Simulating a Rise to a Height by Using Additional Respiratory Resistance

Abstract

The aim of this work was to study the indicators of heart rate variability (HRV) under conditions of additional respiratory resistance (ADR), as an imitation of climbing to a height, in young men with different types of autonomic regulation. The study involved 715 young men aged 19 to 24 years. HRV parameters were assessed by the method of variational pulsometry (BioMouse). Each subject passed two tests lasting 5 min: background, and under conditions of DDS. An ETM 2.0 resistive mask was used to simulate climbing (ADS simulation), in three altitudes: 3000, 9000, 18000 feet. Each person performed only one test; the height of the lift was not reported to him. Based on the results of background testing, two groups were created: the OB group – with balanced sympathetic and parasympathetic influences on HRV (stress index 25–100 c.u., VLF above 240 ms2), the PT group – with a moderate predominance of parasympathetic (vagal) influences (stress index below 25 c.u., VLF above 500 ms2). In the background testing, the OB group was characterized by higher values of the Bayevsky indices (IVR, VPR, PAPR), reflecting the predominance of sympathetic tone, and the PT group had higher values of the variation range of the duration of R–R intervals, RMSSD, SDNN, pNN50%, which are considered markers of increased vagal tone, and the total power of the HRV spectrum TP. Under conditions of ADR, without taking into account the height of the simulated rise, in the OB group, an increase in indicators correlated with vagal activity was revealed: the range of R–R intervals, RMSSD, SDNN, the HF range in the HRV spectrum, with a decrease in the Baevsky indices (IVR, VPR, PAPR, stress index). The increase in spectral measures of HRV associated with sympathetic activity (LF%) ant TP reached the level of statistical significance only when simulating an ascent to an altitude of 18 000 feet. In the PT group, the changes were oppositely directed: a decrease in correlates of vagal activity and an increase in sympathetic tone, regardless of the height of the lift. However, in both groups, the range of R–R intervals increased the most at 9000 feet, which is critical for the development of mountain sickness. Differences in the autonomic regulation of the cardiovascular system in young men determine the direction and severity of shifts in HRV indicators when simulating a rise to a height. In the OB group under conditions of ADR, when simulating a rise to insignificant heights, the indicators associated with vagal activity increase, with an increase in the height of the rise, an increase in parameters reflecting the sympathetic tone joins them. In the PT group, an expected increase in sympathetic tone was found at all altitudes.