Someone explain to me why high altitudes cause a right shift in the OBC

[Blesbok]

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I understand what causes the shift and all that good stuff.

Just for personal reasoning, I am trying to figure out why. At high altitudes you have a lower pO2. Therefore, in order to achieve 90+% O2sat, I would think you would want to left shift it so that lower p02 would give a higher O2 sat. I know that this is wrong, but can someone explain to me the proper reasoning.

 

[bgreet]

If the same % of Hb is saturated at lower elevations and higher elevations, with a lower overall amount of 02 at higher elevations it means that instead of your tissues getting oxygen, it will instead stay stuck to your Hb. Basically you want something (2,3 BPG) to decrease your binding affinity for Hb so that more of the oxygen can disseminate to your tissues instead of just staying stuck to Hb.

 

[Blesbok]

If the same % of Hb is saturated at lower elevations and higher elevations, with a lower overall amount of 02 at higher elevations it means that instead of your tissues getting oxygen, it will instead stay stuck to your Hb. Basically you want something (2,3 BPG) to decrease your binding affinity for Hb so that more of the oxygen can disseminate to your tissues instead of just staying stuck to Hb.

Yes, but I would think you would want to have the same %sat at both altitudes in order to deliver the same amount of oxygen. I know that it increases EPO and all that good stuff at high altitudes for that reason, but I would think that increasing the binding affinity of hemoglobin ...I just figured it out. I wasn't taking into account the lower PaO2 that would also occur at the higher altitudes. I was only thinking about the lower PAO2. 😳

Thanks for the help.

 

[alpha06]

Had the same question...

http://forums.studentdoctor.net/showthread.php?t=488968

Don't know if this helps.....🙄

 

[ReidSternberg]

Yes, but I would think you would want to have the same %sat at both altitudes in order to deliver the same amount of oxygen. I know that it increases EPO and all that good stuff at high altitudes for that reason, but I would think that increasing the binding affinity of hemoglobin ...I just figured it out. I wasn't taking into account the lower PaO2 that would also occur at the higher altitudes. I was only thinking about the lower PAO2. 😳

Thanks for the help.

You mean the lightbulb came because of PaO2... Hmmm.. I wonder how much O2content is contributed by PaO2.. Look back at the equation and see if your reasoning to accept why you have a left shift should be based on PaO2..

Good luck..👍