How Sherpas Function At High Altitude

The superior physical function of Sherpas at high altitudes is due to better blood circulation rather than increased hemoglobin content in the blood.

AsianScientist (Sep. 14, 2018) – People native to the Himalayas have adapted to low oxygen levels at high altitudes by increasing blood circulation to important organs of the body, according to a study published in Experimental Physiology.

Renowned for their superior physical function at Himalayan altitudes where oxygen levels plunge, Sherpas are a staple feature of mountaineering expeditions, serving as guides or mentors to climbers. While lowlanders and other high-altitude populations (such as Andeans and Ethiopians) cope with the reduced oxygen levels at high altitude by increasing the amount of hemoglobin in oxygen-carrying cells of the body, Sherpas do not, thus perplexing scientists.

Researchers from University College London’s Center for Altitude, Space and Extreme Environment Medicine sought to shed light on the physical adaptations of Sherpas by comparing participants drawn from two distinct populations: Sherpas, and an altitude-naive population of lowlanders. The research group was part of Xtreme Everest 2, a translational research program undertaken on Mount Everest.

The scientists first obtained baseline measurements in London (at 50m altitude) and Kathmandu (1,300m altitude) for the lowlander and Sherpa participants respectively. Subsequently, repeated study measurements were taken from participants as they ascended to the base camp of Mount Everest (5,300m altitude).

The research subjects followed an identical ascent profile, which ensured that the physiological challenge, environmental oxygen content and temperature were matched for all participants. Thus, any differences detected between participants would be attributable to their individual physiology rather than variation in the magnitude or duration of exposure to low levels of oxygen at high altitude.

The researchers found that as the amount of surrounding environmental oxygen decreases during the ascent of Mount Everest, Sherpas maintain a greater degree of blood flow and oxygen delivery to the working tissues than the lowlander group. This indicated that Sherpas are able to deliver more oxygen to their bodies, independent of the amount of hemoglobin in the blood.

High levels of hemoglobin make the blood thick and viscous, which not only slows down its flow around the body, but also increases the risk of side effects such as blood clots to the lung. Hence, by favoring increased blood flow and oxygen delivery over high oxygen content, Sherpas maintain the ability to provide their tissues with ample oxygen while minimizing the risk of potentially fatal side effects.

The low levels of oxygen at high altitude can simulate the reduced oxygen faced by critically ill patients in hospital. Therefore, by understanding the physiology behind the Sherpas’ success in low oxygen environments, clinicians could help improve intensive care of patients through the design of novel diagnostic and treatment strategies.

“The mechanisms identified in this study, such as increased blood flow and oxygen delivery to working tissue, feasibly describe an alternative means to aid oxygen delivery in critically ill patients,” said Dr. Edward Gilbert-Kawai of University College London who is a co-author of the study.

“Future research should establish the underlying cellular mechanisms behind this response. Identifying such differences and mimicking those in humans most highly adapted to reduced environmental oxygen may thus reveal novel target pathways that are amenable to drug treatment in the critically ill, and could provide new directions in critical care medicine,” he added.



The article can be found at: Davies et al. (2018) Sustained Vasomotor Control of Skin Microcirculation in Sherpas Versus Altitude-Naïve Lowlanders – Experimental Evidence From Xtreme Everest.

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Source: Physiological Society; Photo: Pixabay.
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