A man in the foreground stands on a snowy slope in boots, pants, a black short-sleeved shirt, baseball cap and winter gloves, before an old prospector's cabin covered in heavy snow, with the tops of dark green pine trees and white snowy mountains reaching up to a bright blue sky in the background.

HAFE: High-Altitude Flatus Expulsion

Often, at high altitude we hear complaints of gas pain and increased flatus in our infant population. Parents often wonder, are we doing something wrong? Is my child reacting to breastmilk, or showing an intolerance to certain foods?  Actually there is another explanation for increased flatus and gas pain in the high-altitude region of Colorado. 

The term HAFE was coined by Dr. Paul Auerbach and Dr. York Miller and published in the Western Journal of Medicine in 1981. Their discovery began In the summer of 1980, when the two doctors were hiking in the San Juan Mountains of Colorado on a quest to summit three 14ers. During their ascent they noticed that something didn’t smell right! As the pair continued to emit noxious fumes, they began to put their scientific brains to work and discovered HAFE. The symptoms include an increase in frequency and volume of flatus, or in other terms an increase in toots! We all have familiarity in watching our bag of potato chips blow up when reaching altitude or our water bottle expanding as we head into the mountains. This reaction is due to a decrease in barometric pressure. Based on Boyle’s law, decreased barometric pressure causes the intestinal gas volume to expand, thus causing HAFE (Skinner & Rawal, 2019).

A graphic illustrating how Boyle's law works: the pressure of a gas increases as its volume decreases.

To my surprise, a gas bubble the size of a walnut in Denver, Colorado (5280 ft) would be the size of a grapefruit in the mountain region of Summit County, CO (8000+ ft)! Trapped gas is known to lead to discomfort and pain. The use of simethicone may have merit in mitigating the effects of HAFE. Simethicone works by changing the surface tension of gas bubbles, allowing easier elimination of gas. This medication, while benign, can be found over the counter and does not appear to be absorbed by the GI tract (Ingold, C. J., & Akhondi, H., 2022). 

While this phenomenon may not be as debilitating as high-altitude pulmonary edema (HAPE), it deserves recognition, as it can cause a significant inconvenience and discomfort to those it inflicts. As the Radiolab podcast explained in their episode The Flight Before Christmas , expelled gas in a plane or car when driving up to the mountains can be embarrassing. While HAFE can be inconvenient, it is a benign condition and a matter of pressure changes rather than a disease or pathological process. We would love to talk more about HAFE at Ebert Family Clinic if you have any questions or concerns!

A bald eagle flies over a misty settled into the valley against the blue-green pine forest of a mountain.
A bald eagle flies toward its nest atop a bare lodgepole pine.

As always, stay happy, safe, and healthy 😊

References

Auerbach, P. & Miller, Y. (1981). High altitude flatus expulsion. The Western Journal of Medicine, 134(2), 173-174.

Chemistry Learner. (2023). Boyle’s Law. https://www.chemistrylearner.com/boyles-law.html

Ingold, C. J., & Akhondi, H. (2022). Simethicone. StatPearls Publishing. 

McKnight, T. (2023). The Flight Before Christmas [Audio podcast]. Radiolab. https://radiolab.org/episodes/flight-christmas

Skinner, R. B., & Rawal, A. R. (2019). EMS flight barotrauma. StatPearls Publishing. 

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