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Updated: Jun 1, 2026

Coherence between Brain Cortical Function and Neurocognitive Performance during Changed Gravity Conditions

Coherence between Brain Cortical Function and Neurocognitive Performance during Changed Gravity Conditions

Published on: May 23, 2011

Human responses to extreme altitudes.

John B West¹

¹Department of Medicine, University of California San Diego La Jolla California CA 92093-0623.

Integrative and Comparative Biology

|June 16, 2011

Summary

Human ascent to extreme altitudes like Mt. Everest involves significant physiological changes, including extreme hyperventilation and respiratory alkalosis, which are not sustainable long-term due to high-altitude deterioration.

Area of Science:

Physiology
Altitude Medicine
Human Adaptation

Background:

The highest points on Earth approach the limits of human tolerance to hypoxia.
Physiological responses to high altitude include acclimatization, evolutionary adaptation, and acute responses to extreme altitudes.
Extreme altitude ascent involves significant physiological alterations incompatible with extended stays, a phenomenon known as high-altitude deterioration.

Purpose of the Study:

To contrast the physiological responses to extreme altitude with acclimatization and evolutionary adaptation.
To investigate the key physiological changes enabling human survival at extreme altitudes.
To understand the mechanisms behind high-altitude deterioration.

Main Methods:

The study focuses on physiological responses observed at extreme altitudes, such as the summit of Mt. Everest.

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Last Updated: Jun 1, 2026

Coherence between Brain Cortical Function and Neurocognitive Performance during Changed Gravity Conditions

Coherence between Brain Cortical Function and Neurocognitive Performance during Changed Gravity Conditions

Published on: May 23, 2011

Key physiological parameters like alveolar P(CO(2)), arterial pH, arterial P(O(2)), maximal oxygen consumption, and blood lactate levels were analyzed.

Comparisons were drawn with acclimatization and evolutionary adaptation to high altitude.

Main Results:

Extreme hyperventilation is a critical response at extreme altitudes, lowering alveolar P(CO(2)) and causing respiratory alkalosis (arterial pH > 7.7).
This alkalosis enhances hemoglobin's oxygen affinity, a shared trait with other animals in hypoxic conditions.
Arterial P(O(2)) on Mt. Everest's summit is low (~30 mmHg), decreasing with exercise due to diffusion limitation; maximal oxygen consumption is limited, and anaerobic metabolism is reduced.

Conclusions:

Physiological changes enabling extreme altitude ascent, particularly extreme hyperventilation and associated alkalosis, are distinct from acclimatization and adaptation and lead to high-altitude deterioration.
The increased oxygen affinity of hemoglobin due to alkalosis is a key survival mechanism at extreme altitudes.
Understanding these responses is crucial for managing human presence in extreme high-altitude environments.