Contribution of Hypoxic Exercise Testing to Predict High-Altitude Pathology: A Systematic Review.

Thomas Georges,Sophie Ferreol,Alban Fouasson-Chailloux,Pierre Menu,Marc Dauty,Camille Le Blanc

doi:10.3390/life12030377

Thomas Georges, Sophie Ferreol + Show 4 more

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https://doi.org/10.3390/life12030377

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Abstract

Altitude travelers are exposed to high-altitude pathologies, which can be potentially serious. Individual susceptibility varies widely and this makes it difficult to predict who will develop these complications. The assessment of physiological adaptations to exercise performed in hypoxia has been proposed to help predict altitude sickness. The purpose of this review is to evaluate the contribution of hypoxic exercise testing, achieved in normobaric conditions, in the prediction of severe high-altitude pathology. We performed a systematic review using the databases PubMed, Science Direct and Embase in October 2021 to collect studies reporting physiological adaptations under hypoxic exercise testing and its interest in predicting high-altitude pathology. Eight studies were eligible, concerning 3558 patients with a mean age of 46.9 years old, and a simulated mean altitude reaching of 5092 m. 597 patients presented an acute mountain sickness during their altitude travels. Three different protocols of hypoxic exercise testing were used. Acute mountain sickness was defined using Hackett’s score or the Lake Louise score. Ventilatory and cardiac responses to hypoxia, desaturation in hypoxia, cerebral oxygenation, core temperature, variation in body mass index and some perceived sensations were the highlighted variables associated with acute mountain sickness. A decision algorithm based on hypoxic exercise tests was proposed by one team. Hypoxic exercise testing provides promising information to help predict altitude complications. Its interest should be confirmed by different teams.

Highlights

Millions of people engage in mountain sports activities worldwide
acute mountain sickness (AMS) is linked to cerebral vasodilatation secondary to hypoxemia, which induces an increase in brain volume, a decrease in compliance and an increase in intracranial pressure [5]
Exercise in hypoxia, compared to rest in hypoxia, causes greater severity and incidence of acute mountain sickness [20]. Those tests aimed to evaluate physiological adaptation to hypoxia, as well as sensitivity of the chemoreceptors to hypoxic stress which are essential in adaptation to hypoxemia [21], and to highaltitude pathology

Summary

Introduction

Millions of people engage in mountain sports activities worldwide. Nepal counted nearly 1.2 million tourists in 2019, compared to 350,000 in 1995 [1]. Personal physiological response to hypoxia is complex and varies widely between individuals [9] Rest testing such as electrocardiogram or pulmonary function testing failed to predict HAI [2,10]. Exercise in hypoxia, compared to rest in hypoxia, causes greater severity and incidence of acute mountain sickness [20] Those tests aimed to evaluate physiological adaptation to hypoxia, as well as sensitivity of the chemoreceptors to hypoxic stress which are essential in adaptation to hypoxemia [21], and to highaltitude pathology. Worsening hypoxemia by exercise could improve the performance of those tests by challenging coping mechanisms [22,23] These hypoxic tests are widely practiced in France, and are prescribed for research institute members or diplomatic employees working in some countries in South America [24].

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