THE HIGHER THE ALTITUDE, THE BETTER THE TOLERANCE TO HYPOXIA: A PARADOXICAL PHYSIOLOGICAL RESPONSE

DOI:10.23670/RC.2025.02.06

Abstract

Life fundamentally depends on oxygen, which constitutes 20.9 % of Earth's atmosphere at any altitude. The most abundant element in the human body is oxygen (63 %). Residents at sea level (BP = 760 mmHg) inhabit an oxygen-rich environment where the Inspired Oxygen Pressure (PIO2) is 150 mmHg. The transport of oxygen from the environment to the mitochondria to generate energy through ATP relies on this pressure gradient. Residents at sea level have little tolerance to hypoxia (low oxygen levels). In contrast, humans living at high altitudes tolerate it very well. Humans at high altitude tolerate hypoxia much better. This article proposes a hypothesis that potentially explains hypoxia tolerance and survival. A careful examination of the unavoidable changes at 3500 meters above sea level suggests a decrease in arterial partial oxygen tension (PaO2), an increase in hemoglobin (Hb), and a reduction in carbon dioxide partial pressure (PaCO2). These last two variables allow us to propose a formula: Hypoxia tolerance = (Hb/PaCO2) * 3.01. In this article, we present evidence of the relationship between hemoglobin and PaCO2 concerning hypoxia tolerance.