Peripheral chemoreceptors and human adaptation to high altitude

Area of Science:

• Physiology
• Altitude Medicine
• Respiratory Regulation

Background:

• The hypoxic chemoreflex is crucial for maintaining ventilation during low oxygen exposure.
• Understanding respiratory control adaptations at high altitudes is vital for acclimatization and health.

Purpose of the Study:

• To investigate basal hypoxic chemoreflex drive and respiratory responses to hypoxia at varying altitudes.
• To determine the influence of altitude on the chemoreflex mechanism of respiratory control.

Main Methods:

• Studied 142 healthy individuals aged 13-50 years at altitudes of 760 m, 2800 m, and 3600 m.
• Assessed respiratory responses to poikilocapnic hypoxic gas mixtures (pO2 = 9.33 kPa).
• Measured basal hypoxic chemoreflex drive and ventilation changes after oxygen inhalation.

Main Results:

• At 760 m and 2800 m, the chemoreflex contributed 13-18% to eupnoic ventilation across all ages.
• At 3600 m, no decrease in ventilation occurred after oxygen inhalation, suggesting altered chemoreflex regulation.
• Respiratory responses to hypoxia were qualitatively similar across all studied altitudes.

Conclusions:

• The arterial chemoreceptor activity threshold shifts towards lower PACO2 values at 3600 m.
• Alterations in chemoreceptor excitability or central inhibition may explain the blunted hypoxic response at high altitude.
• Respiratory centers are implicated in the diminished ventilatory response to hypoxia at 3600 m.