Hypoxic ventilatory response

Hypoxic ventilatory response (HVR) is the increase in ventilation induced by hypoxia that allows the body to take in and transport lower concentrations of oxygen at higher rates.

It is initially elevated in lowlanders who travel to high altitude, but reduces significantly over time as people acclimatize.

[1][2] In biological anthropology, HVR also refers to human adaptation to environmental stresses resulting from high altitude.

It is a direct result of the decrease in partial pressure of oxygen in arterial blood, and leads to increased ventilation.

[2] Especially for lowlanders who traverse past 6000 meters in altitude, the limit of prolonged human exposure to hypoxia, HVR may result in hyperventilation and ultimately the deterioration of the body.

However, lower oxygen partial pressure induces post-transcriptional modification of HIF-1α, allowing HIF-1α to dimerize with HIF-1β to form HIF-1.

HIF-1 induces many physiological changes that help the body adapt to the lower availability of oxygen including angiogenesis, increased erythropoietin production, and promoting anaerobic metabolism.

The process is triggered by the peripheral nervous system's detection of a low blood oxygen level.

A study conducted in dogs investigated how their cardiovascular systems respond to various levels of oxygen before and after being given MK-801, which is a glutamate antagonist.

[19] Populations that have permanently settled in high altitude locations show virtually no reaction to acute hypoxia.

Natives of the Andes and the Himalayas have been shown to develop adaptation to hypoxia from birth to neonatal years in the form of larger lungs and greater gas exchange surface area.

[24] The altitude adaptations also appear to be less permanent than those seen in the Tibetan populations, as the Andeans have a much higher prevalence of Chronic Mountain Sickness (CMS), where the body develops a harmful reaction to low oxygen levels over many years.

The Sherpa are able to make much more money[28] acting as travel guides due to their local knowledge, and climbing ability.

Genetic evidence suggests that the Tibetan peoples diverged from the larger Han Chinese population any time around 1,000 B.C.E.

For example, Tibetans have evolved a greater oxygen saturation during infancy, leading to a lower rate of child mortality than experienced by non-adapted populations at altitude.