Indicators of individual hypoxia resistance — a way to optimize hypoxic training for children

Objective. To develop a protocol for a normobaric hypoxic test and criteria of resistance assessment — normobaric hypoxia sensitivity in children.

Characteristics of children and research methods. 56 healthy children aged from 8 to 12 years underwent a hypoxic test inhaling gas mixture with 10—11% of O₂ through mask to create hypoxemia conditions (SpO₂ = 80%). The authors used a normobaric hypoxic device (certified in the Russian Federation) to produce hypoxic and hyperoxic gas mixtures — ReOxy Cardio (S.A. Aimediq, Luxembourg) with an integrated pulse oximetry sensor (Masimo Rad-5, USA).

During hypoxic test they monitored the arterial blood oxygen saturation (SpO₂) and heart rate (HR, bpm), and there were automatically recorded the individual minimum values of SpO₂ level (SpO₂ min) and maximum heart rate (HR max). A “hypoxic phase” was terminated in case of decrease in SpO2 to 80% or lower, or breathing with a hypoxic gas mixture during 9 minutes. An additional criterion for termination was an increase in HR by 30% and higher over the initial level. After reaching one of the described criteria, the teenagers began to breathe ambient air and the authors determined the recovery time of SpO₂ to 97%. In addition, the authors calculated the hypoxic index as desaturation/reoxygenation time ratio.

Results. The authors developed a protocol for conductance and assessment of hypoxic resistance in children and adolescents. There were determined three types (phenotypes) of response to dosed normobaric hypoxia in adolescents: low, medium and high levels of dosed hypoxic stimulus resistance.

Conclusion. The proposed hypoxic test protocol reflects the individual hypoxia tolerance and can be used to individualize hypoxic therapy courses, as well as additional diagnostic tool in assessing the adaptive capabilities and non-specific reactivity in children.

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