High altitude...inc./dec. PCO2??

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alpha06

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I'm studying the respiratory system in FA2008 and am confused in one of the topics...

In the respiratory system, high altitude will shift the O2/diss curve to the right. Also an increase in CO2 will shift the curve to the right....

BUT I thought at high altitudes, you hyperventilate, which would decrease your CO2.....but a decrease in CO2 shifts the curve to the left...???

See my confusion.😕

And it also says that there is an increase in renal excretion of bicarb to compensate for resp. alkalosis (decreased CO2)...

So why does a high altitude give a right shift then and how does it correlate to CO2???

Very confused. If someone could clarify, that would be great!
 
  • Hypoxemia causes respiratory alkalosis
  • Alkalosis shifts curve to the left BUT
  • Alkalosis activates PFK and so causes increased 1,3 BPG which is converted to 2,3 BPG
  • 2,3 BPG shifts curve to the right
So, high altitude shifts right

Special thanks goes to uncle Goljan 😎

From RR pathology, 2nd edition
 
So then....

high altitude => decreased PCO2 => resp. alkalosis (an initial left shift)

BUT

alkalosis => .... => increased 2,3-DPG (overwhelmes initial left shift to move curve to the right)

Does that sound right??
 
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