April 8, 2013
Yak Skiing and Altitude Disease Resistance
Yaks and llamas are often man’s crutch on high altitude treks. These animals haul large gear loads through the thin air of the Himalayas and tire markedly less quickly than their masters. The high altitude power of the Yak is also harnessed to allow skiers to ski up mountains in a sport called Yak Skiing.
What this have to do with anything?
These animals also have a remarkable resistance to health conditions that plague humans in razor thin air such as pulmonary hypertension and high altitude pulmonary edema. Scientists have studied these animals to uncover the biological basis for their ability to thrive and avoid high altitude related diseases.
Some of these biological adaptations include altered hemoglobin affinity for oxygen and larger lung capacities than lower altitude dwelling cattle. A lesser known adaptation, however, is a small structural difference in pulmonary arteries that has a large impact.
Humans and there Muscular Arterioles:
Humans, Yaks, Llamas, and every other mammal possess a pulmonary artery tree that carries deoxygenated blood from the heart to the lungs. These arterial branches are very thin and become constricted in humans at high altitude, but not in Yaks or Llamas.
This human constriction response results from a dual structure of a muscular ring and lamina to support arterioles. When exposed to hypoxia, this structure becomes increasingly muscularized. One may thing that stronger blood vessels would improve blood circulation in the lungs and be beneficial, but it ultimately causes the vessels to constrict. Constriction increases pulmonary blood pressure and increases the risk of HAPE and pulmonary hypertension.
Yaks and Llamas have a single arteriole structure consisting of one supporting lamina. As a result of this structure muscularization, and thus pulmonary vasoconstriction does not occur at high altitude.
So What Does Viagra Have to Do With All of This?
Sildenafil citrate, or Viagra dilates pulmonary blood vessels. It is currently being used effectively as treatment and prevention of HAPE as well as high altitude pulmonary hypertension.
In addition to preventing these conditions Viagra has also been shown to improve physical performance of cyclists at high altitude. This makes it a valuable alternative to Diamox, which will likely worsen athletic performance at moderate altitude where competitions are held.
Has anyone ever used Viagra as a preventative for altitude sickness?