General and integral analysis of cardiac effects under acute hypoxia before and after intermittent hypoxic training in humans in Northern Russia

BACKGROUND: One of the specific and underexplored issues in human ecological physiology and medicine in the North is cardiac function during hypoxemia in the cold season. This formed the basis of the current study.AIM: To examine the changes in the bioelectrical activity of the heart and the integral typology of responses to acute hypoxia before and after interval normobaric hypoxic training in healthy individuals during the winter season in Northern Russia.MATERIALS AND METHODS: The study included 29 men (mean age 20.2±0.31 years) exposed to acute hypoxia (12.3% O2) for 20 minutes. Blood oxygenation (SpO2%) and three amplitude and temporal ECG parameters were recorded at baseline and on Days 1, 7, and 16 following intermittent normobaric hypoxic training. Integral values of the heart’s chronotropic and inotropic responses were determined.RESULTS: At baseline, during acute hypoxia, P1II (р=0,005) and P-Q (р=0,006) increased, while RII, T1II, R-R, and Q-T (р 0,001) decreased. Following intermittent normobaric hypoxic training, the deviation in T1II during acute hypoxia reduced from Day 1 (p=0.030) to Day 16 (p 0.001), and P1II decreased by Day 16 (p=0.020). Deviations in T1II and Q-T correlated consistently with those in SpO2%. During episodes of acute hypoxia, mesoreactive responses were observed in 42.5-47.1% of cases, hyperreactive responses in 24.1-29.9%, and hyporeactive responses in 27.6-28.7%. Integral values of polar chronotropic and inotropic reactions to acute hypoxia increased significantly from Day 7 following intermittent normobaric hypoxic training compared to baseline.CONCLUSION: Intermittent hypoxic training reduces alterations in the bioelectrical activity of the right atrium during acute hypoxia, and mitigates the suppression of ventricular myocardial activity during the rapid terminal repolarization phase. Ventricular systole becomes increasingly dependent on developing hypoxemia. While the quantitative proportions of polar chronotropic and inotropic responses remain unchanged, their integral mean values increase significantly

Anesthesia · Blood pressure · Cardiology · Chronotropic · Heart rate · Hypoxemia · Inotrope · Intermittent hypoxia · Oxygen · Oxygenation · Cardiac Arrest and Resuscitation · Chemistry · Heart Rate Variability and Autonomic Control · High Altitude and Hypoxia · Medicine · Internal Medicine

• Variations of human heart bioelectrical signals at hypoxic exposure

  Open Access•Mihail I Bocharov, Aleksandr S Shilov•Ekologiya Cheloveka (Human Ecology•2022

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