Lessons from chronic intermittent and sustained hypoxia at high altitudes

Area of Science:

• Physiology
• Hypoxia research
• Sleep medicine

Background:

• Recurrent sleep apnea (RSA) mimics chronic intermittent hypoxia (CIH), potentially causing distinct carotid body adaptations compared to sustained hypoxia (SH).
• Reactive oxygen species (ROS) generation is implicated in CIH, influencing hypoxia-inducible factors (HIF-1s) and gene expression to restore oxygen levels.
• Limited research exists on CIH effects at high altitudes (HA), particularly concerning peripheral chemoreception.

Purpose of the Study:

• To re-examine existing views on CIH effects, focusing on peripheral chemoreception.
• To explore the role of hypoxia-inducible factors (HIF-1s) in high-altitude adaptations to recurrent sleep apnea.
• To investigate the higher prevalence of RSA in lowlanders at HA due to ventilatory sensitivity.

Main Methods:

• Review and re-examination of existing literature on CIH, SH, and peripheral chemoreception.
• Analysis of adaptations in oxygen sensing mechanisms within the carotid body.
• Comparative study of lowlanders and high-altitude natives (HAN) regarding RSA at HA.

Main Results:

• RSA may induce unique cellular functions in the carotid body, differing from SH.
• Hypoxia-inducible factors (HIF-1s) are central to high-altitude adaptations, though mechanisms remain unclear.
• Lowlanders exhibit higher RSA prevalence at HA due to heightened ventilatory sensitivity to hypoxia.

Conclusions:

• The mechanisms underlying HIF-1s' role at high altitudes require further investigation.
• Understanding RSA's impact on oxygen sensing is crucial, especially in diverse environments like high altitudes.
• Further research is warranted to explore the unique adaptations triggered by recurrent sleep apnea in the context of high-altitude physiology.