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Throughout the expedition


Demonstrate the effect of altitude on the oxygen carrying capacity of human blood.


With an increased oxygen demand, and decreased oxygen supply the i2P runners on the Salar run the risk of developing an oxygen deficit. The oxygen deficit can cause altitude sickness. The best way to prevent altitude sickness is by gradually ascending to altitude. This allows the human body to naturally compensate to decreased atmospheric oxygen through a series of adaptations. One of the adaptations is an increase in blood count. In response to low blood oxygen, red blood cell counts increase within days of arriving at altitude.


We will again take blood samples from the expedition members and analyze them using the ISTAT measurement device. We will take measurements at lower and higher elevations to show the acute (short term) responses and then repeat the measurements 7 days into the expedition to show the more chronic (long term) adaptations that happen in the body.

Experiment Report & Results

Oxygen is the most important element for life. Without oxygen we die within minutes. Our entire cardio-pulmonary system (heart, lungs & blood) is designed to transport oxygen from the environment to the cells in our body that use oxygen to create the energy that in turn fuels metabolism in every part of our body. Our trip to Bolivia is providing us with an excellent opportunity to understand oxygen metabolism in the human body. Check out how much Youth Ambassador Ryan Montgomery's blood oxygen pressure decreased as we moved from Santiago to the Salar de Uyuni.

The lower pressure of oxygen in our blood means that less oxygen is getting to the muscles, brain and other organs.

This makes running here really tough - check out this video of Youth Ambassador Ashley Hassard talking about how she is feeling after her first run on the Salar, and what happened to me when I went for a 400 m sprint at one point during today's run. Fortunately, spending time at altitude results in beneficial changes inside our bodies that last for months. At the end of today's video I have an interview with Ray Zahab about his experiences with adaptation during the Atacama Extreme Expedition.

The body makes some interesting internal changes to help deal with this drop in blood oxygen pressure. Specifically the kidneys start increasing the amount of fluids that we excrete (we pee much more here). That increases the concentration of red blood cells in our blood - that's called our hematocrit. The pathway that oxygen takes to our cells continues from the lungs into the red blood cells. Red blood cells, or erythrocytes, are specialized cells that are present in the blood (other components of blood include white blood cells and the clear fluid, plasma). The percentage of the blood that is composed of red blood cells, called hematocrit, is normally about 45%.

Check out the increase that we've seen from Santiago to the Salar.

The increases in hematocrit also caused an increase in hemoglobin. Hemoglobin is the molecule inside our red blood cells that carries oxygen to our cells.

These incredible adaptations help our bodies carry oxygen to our tissues even in extreme environments like the altiplano of Bolivia. To leave you - here is a photo of a mountain on the edge of the Salar at dusk.

-- Greg Wells, PhD.
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