Features of the reactivity of the human cardiovascular and respiratory systems during stress tests in different climatic conditions and in the dynamics of adaptation to the conditions of the North
Abstract
Expanding the ability of a person to reach and use areas of the planet with extreme climatic conditions makes relevant studying indicators of relocants’ performance. To solve this problem, functional load tests are used.
The aim of the study was to assess changes in the cardiovascular and respiratory systems during respiratory stress tests (mild mixed hypoxia/hypercapnia with voluntary respiration or respiration at a frequency of 6 cycles per minute) in participants of high-latitude sea expeditions. These changes were compared with respective data of permanent residents of the middle zone (Moscow region) or the North (Murmansk region).
Materials and methods. The study was carried out using the device complex "spiroarteriocardiorhythmograph" (OOO "INTOX", St. Petersburg, Russia). 25 inhabitants of the Moscow region, 43 inhabitants of the Murmansk region, and 30 participants of high latitude expeditions were examined, a total of 98 men, aged 30 to 60 yrs. The expedition participants were tested before going to sea and immediately after returning. The studies included three consecutive 2-min recordings: without a spirometry mask on (control), with a mask on with spontaneous breathing (trial 1), and with controlled breathing at a frequency of 6 cycles per minute (trial 2). We assessed the degree of change (%) in the recorded indicators during the stress tests.
Results. No differences in reactivity of the cardiovascular and respiratory systems during stress tests were found between residents of Moscow and of the North. During stress tests, expedition participants showed no changes in heart rate reactivity and variability, cardiac performance, or sensitivity of spontaneous arterial baroreflex. However, for 26–28 days of the expedition, the blood pressure (BP) reactivity and indicators that reflected the BP regulation have changed. In the test with a mild stress, the average increase in systolic BP was followed by a decrease, along with an increase in the total power of the BP variability spectrum and a decrease in the reactivity of the relative power of the low frequency range, a correlate of sympathetic activity. On the contrary, when performing a more difficult test with controlled breathing, a decrease in the total power of the BP and BP variability spectra along with a tendency for a decrease in tidal volume was noted. The indicators of the cardiovascular and respiratory system reactivity in participants of high-latitude expeditions who did not reside in this region before leaving the port of departure did not differ from those in the inhabitants of the North. However, these indicators significantly exceeded those of permanent residents of the middle zone. Changes in reactivity during the expeditions brought these indicators closer to those of Muscovites.
Conclusion. Urgent adaptation to the conditions of the Far North is accompanied by a decrease in the respiratory system reactivity and by changes in the cardiovascular system reactivity during respiratory stress tests.
