- Exposure to high altitudes trigger changes in the numbers of red blood cells in the body
- This is because the air is ‘thinner’ at high altitudes
This means that the barometric pressure of the air is reduced and so is the partial pressure of oxygen
- To cope, the body compensates by increasing the mass of red blood cells and haemoglobin
- Given a chance to adapt, red blood cells can occupy 60% of blood volume instead of 45%
- This change is demonstrated on an oxygen dissociation graph with a shift to the left (the upper line)
The oxygen dissociation graph of the body at high altitude is similar to that of foetal haemoglobin. In both cases, the line is shifted to the left compared to adult haemoglobin at lower altitudes.