Features of Cardiorespiratory System Indicators in the North and Their Dynamics in Participants of Arctic Expeditions and Wintering at the Polar Station “North Pole-41”

The aim of this work was a synchronous study of cardiovascular and respiratory indicators with a search for their relationship among residents of different latitudes and in high-latitude Arctic expeditions. The effect of place of residence on cardiorespiratory system parameters was studied in 113 men - workers of industrial enterprises (Sochi, Moscow, North). Adaptation to short-term Arctic expeditions was assessed in men (43 people in total, aged 35-60 years); 15 Moscow residents of the same age served as a control. The dynamics of adaptive processes in Arctic expeditions was assessed based on the results of testing before and after the start of the expeditions, on SP-41 - monthly. Two two-minute recordings were made on the spiroarterioacardiorrhythmograph (SACR) device: with voluntary breathing and with controlled breathing at a frequency of 6 cycles per minute. The amplitude-temporal values of the average respiratory cycle were assessed, as well as the statistical parameters of heart rate variability (HRV) SDNN and RMSSD. It has been shown that residents of the North, in contrast to both southerners and Muscovites, are characterized by a shorter inspiration. In the HRV indices, northerners showed lower SDNN values compared to Sochi residents, with a similar trend (p = 0.065) for the RMSSD value. Only northerners had correlations between the respiratory and HRV indices. We did not detect any dynamics of the assessed indices of the cardiorespiratory system in short-term (up to 4 weeks) Arctic expeditions, neither with any of the breathing patterns used, nor with double or triple testing. In monitoring at SP-41, it was found that 2-3 days after the start of the expedition, under controlled breathing conditions, the RMSSD index was reduced. A month after the start of wintering, a decrease in the tidal volume in the controlled breathing test (at the trend level, p = 0.078) and a decrease in the SDNN and RMSSD indices were recorded. In high-latitude expeditions, a decrease in autonomic regulation indicators is observed against the background of a reduction in volumetric, but not time-related indicators of the respiratory cycle, which is revealed only when breathing at a frequency of 6 cycles per minute.