O2 Disosciation curve

[jae01]

I am a bit confused on a question about the hemoglobin/O2 curve.

At high altitude, does it shift left or right?

I remember Kaplan says left, but there's an examcracker question about it, and the answer is right.

Reason for it shifting right according to Examcracker is because a right shift reflects a decrease in affinity of hemoglobin for oxygen, which promotes oxygen release to the tissues.
So when we're talking about the curve, we talk about it at the tissue level????

If someone can be so kindly as to please help me with this dilemma.

Thank you!

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[rocuronium]

To understand this, you have to look at everything that is happening at altitude.

The most obvious thing is the decrease in partial pressure of O2. The body's natural response to hypoxia is to increase respiratory rate. But this is only half of the picture. What happens to the CO2 levels when you increase respiratory rate? By blowing off CO2 you lower the pCO2.

What this does is cause a respiratory alkalosis. The pH of the blood goes up. Knowing this, we should be able to answer your question.

When the pH of the blood goes up, the affinity of hemoglobin for oxygen also goes up. This is a left shift. This means that potentially less oxygen will be released to the tissues.

It is important to remember that these changes are acute. Over time, the body will respond. The kidneys will try to eliminate excess bicarb to lower the pH to normal.

So to answer your other question, you have to examine hemoglobin's affinity for oxygen in its current environment.

Just for a bit of trivia, think about what happens during asphyxiation. Does hemoglobin's affinity for oxygen go up or down? If you can answer that, you probably understand the concepts well enough.

 

[TieuBachHo]

jae01

At high altitude, does it shift left or right?

The answer is Right Shift. It's important to know that the O2 uptake of hemoglobins in capillaries is short-lived. So less pO2 at high altitude results in less O2 being saturated.


So when we're talking about the curve, we talk about it at the tissue level????

Not really, it can be in the lung, tissues, or whatever. There are several factors involve though. All High DPG/BPG, low pH, high temperature, low pO2, and high level of CO2 generally cause Right Shift.

***The explanations given might depend on the passage given. However, they are right most of the time; otherwise, no one would buy their materials . Just in my own exprience, I would try to understand them first before I dismiss them.***