Any good tricks/neumonics to learn gas exchance, hemoglobin shifts?

[ej37]

I've bee having some trouble with conceptually, just using the standard H20+ Co2 -> HCO3- + H+, although it seems pretty limited, as increased CO2, increased H+ all shift the right, and don't seem to say much about the equal exchange in the lungs. Anyway, I'd appreciate it anyone could help, thanks!

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[FutureInternist]

First AID has the mnemonic CADET face Right
C - CO2
A - Acid / Altitude
D - DPG
E - Exercise
T - Temperature

All of these cause the Hgb curve to shift to the right --> easier unloading of O2

 

[rocuronium]

I think about it this way. What are the conditions around a hard working muscle?

It needs oxygen (right shift).
It has high temperature.
It has lots of CO2.
It has a low pH.
It has high BPG.

If you think about it this way, you don't need to memorize, you just use an example of something that you know, and work with that. It is just the opposite in the lungs. In the lungs, you want to pick up oxygen, so it is a left shift, which is the opposite of everything above.

None of this should have to be memorized.

 

[nfg05]

What are the conditions around a hard working muscle?

It needs oxygen (right shift).

...

In the lungs, you want to pick up oxygen, so it is a left shift, which is the opposite of everything above.

None of this should have to be memorized.

For clarification, are you implying here that Hg in the lungs has a different affinity than Hg in the muscle at a given point in time? I was under the impression that although external factors can shift Hg affinity curves, ALL Hg in the body has its curve shifted left or right, regardless of where in the body it is.

 

[rocuronium]

For clarification, are you implying here that Hg in the lungs has a different affinity than Hg in the muscle at a given point in time? I was under the impression that although external factors can shift Hg affinity curves, ALL Hg in the body has its curve shifted left or right, regardless of where in the body it is.

There definitely is a difference in affinity based on location. Think about what would happen if the Hgb at the tissues had the same affinity for oxygen as Hgb at the lungs. No oxygen would be delivered to the tissues. The physiological conditions at the lungs are conducive for oxygen binding, and the conditions at the tissues are conducive for oxygen removal.

If you want to do a little more reading, look up the Bohr and Haldane effects.

Now, while physiological right and left shifts occur in the body, they can also occur systemically as you have mentioned. An example of this would be acidemia or alkalemia. If the pH of the blood shifts, then all of the Hgb in the blood will be shifted.

I hope that clears things up!