Antarctic station Vostok as an analogue of a future lunar base: physiological reactions of the human cardiorespiratory system during a year-long exposure to the conditions of hypobaric hypoxia, isolation and hypokinesia

A number of physiological investigations focused on human cardiorespiratory system have been conducted at Vostok station in Central Antarctica during the wintering of 2019.

During the one-year expedition at the Vostok station, the cardiorespiratory system gradually adapted to the unusual conditions of life and work in the isolated, confined and extreme (ICE) environment of Central Antarctica.

We hypothesized that during a long stay in the conditions of the Central Antarctica the adaptation strategy to physical environmental conditions for representatives of two age groups will differ, which will be evident from the dynamics of indicators of the functioning of the cardiovascular system and when assessing the autonomic nervous system status.

The level of blood oxygen saturation stabilized by the second month and was in the range of 86.0-91.0%, which corresponded to a reduced partial pressure of oxygen in the inhaled air. In terms of the respiratory system, central sleep apnea was noted in all subjects throughout the study. Quantitative analysis revealed that the average number of apneas per hour was 43, and their average duration was 25.2 seconds. The maximum apnea number was recorded at the beginning and middle of wintering, while before the end of the expedition the episodes became rarer. In all age groups there was a shortening of the PQ interval, with a tendency towards normalization by the end of wintering, while in the first age group the shortening of the interval was more significant than in the second, which apparently can be explained by a more pronounced active reaction of the sympathetic nervous system of polar explorers of the first age group.

Adaptive Potential Index (API) level remained practically unchanged throughout the wintering period in 9 out of 11 members of the expedition. The API value was predominantly in the range from 2.11 to 3.20 points, which corresponds to the level of “adaptation stress”. The autonomous nervous system (ANS) status was assessed by Kerdo Index (KI) values. KI positive dynamic was noted in 90% of cases by the 5th month of wintering. A direct correlation was found between the degree of positive shift in the KI value and the age of the participant. The gained results do not allow us to state that ANS has fully adapted to the conditions of life and work at the station. The results of this investigation demonstrate stable and positive adaptation trend to the ICE environment of Central Antarctica throughout the study period, regardless of age and wintering experience.