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02 dissociation curves and altitudes

i'm really crap at this part of my spec..could someone explain in 'dummy' terms how altitude & o2 dissociation curves are related? how do you work out the partial pressure at a certain height? also, what is 'affinity'? i'm so confuzzled, any help appreciated! :frown:

Reply 1

corkskrew

There is a lower partial pressure of oxygen at greater heights
More red blood cells and more Hb is reqd to "make the most" of a lower than normal pp(O2)
A greater affinity means oxygen will 'stick to' the Hb better
The standard curve of %age saturation against p(O2) is s-shaped
At greater altitudes the surve shifts to the left, as the p(O2) is lower, so a greater affinity is needed to get the correct %age saturation.
The steep regions of the curve are the range where it is easy for O2 to bind onto he Hb. At the extremes of the pO2 it is very hard for O2 to combine with Hb.
Also, when one O2molecule has bound to the Hb the affinity increases - this is what gives the S shape.

Hope this helps. All the best

Reply 2

glance

If you look at the oxygen dissociation curve, you'll see the partial pressure of oxygen along the bottom. As that partial pressure of oxygen increases, the saturation of haemoglobin (along the vertical axis) also increases.

At normal altitude, the partial pressure of oxygen will be high and therefore the oxygen saturation of haemoglobin will also be very high. At high altitude, however, the partial pressure of oxygen will be lower and therefore the oxygen saturation of haemoglobin will also be lower.

In other words, at high altitude your haemoglobin can carry less oxygen than at sea level. This means you will need more haemoglobin to provide the body with sufficient oxygen.