Oxyhemoglobin Dissociation Curve

[KnightRN]

I am trying to understand the application of the OHDC. I understand what causes a shift to the right or to the left. I am just kind of stuck on what we apply it to??? In what situation would this curve be used in the real world??? Understanding it's use will help me understand it better.

[CBsMommy]

I'm not sure what you mean by what we apply it to? The dissociation curve is there to describe the amount of hemoglobin (the part of the red blood cell O2 is bound to) in relation to the amount of O2 in the blood. I've never heard of it used on a regular med-surge floor however I'm sure this would be used in critical care either to watch pH balance and/or O2 levels.

I could also see this being used in a case of CO poisoning.

This is only speculation. We don't learn this in my nursing school however I have run across it in critical care books.

[MN-Nurse, ASN, RN]

I'm not sure what you mean by what we apply it to? The dissociation curve is there to describe the amount of hemoglobin (the part of the red blood cell O2 is bound to) in relation to the amount of O2 in the blood. I've never heard of it used on a regular med-surge floor however I'm sure this would be used in critical care either to watch pH balance and/or O2 levels.

I could also see this being used in a case of CO poisoning.

This is only speculation. We don't learn this in my nursing school however I have run across it in critical care books.

We learned about it in physiology and my instructors waved their hand at it in nursing school.

The value of learning it is the same as learning what a chloride shift is, it gives you a deeper understanding and insight into physiological processes. Some questions to ask are "What changes oxygen's affinity for hemoglobin, causing the curve to shift left or right?" Where is it good to have higher or lower affinities? (tissues vs lungs).

[ckh23, BSN, RN]

It is very relevant in the ICU with ABG's. A patients PH, CO2 and temp are going to effect the curve, so in order to get an accurate picture of oxygenation in a patient, these things need to be taken into account. However, in the hospital we can get spoiled because the lab usually calculates the changes according to the abg values.

[CBsMommy]

It is very relevant in the ICU with ABG's. A patients PH, CO2 and temp are going to effect the curve, so in order to get an accurate picture of oxygenation in a patient, these things need to be taken into account. However, in the hospital we can get spoiled because the lab usually calculates the changes according to the abg values.

I've never seen this used in the ICU, I agree, we usually just get it from the lab. The MD's might use it though and from what I've seen online, the discussions are more MD directed than nursing directed.

[HouTx, BSN, MSN, EdD]

AH - one of my favorite areas of diagnostic trivia.... It's very important factor in diagnosing complex, multi-systemic pathology, but you may not see it referenced in progress notes because they usually only refer to the interventions, not the underlying analysis/critical thinking that is going on.

As PP mentioned, it explains why CO poisoning produces that cherry red appearance on the skin. The 'curve' is also instrumental in detecting underlying issues that are not apparent at first glance. For instance, it can be an early warning of impending sepsis; by understanding the curve, it is easy to see why oxygenation is a problem even though data seems normal - plenty of "o's" in the blood, but tissue can still be compromised. "Shift happens" in patients who have received massive amounts of blood - due to alterations in blood enzymes. And of course, any significant change in pH will push the curve also.

Seriously, if you want to learn a bunch - just express interest the next time a Hematologist is consulted on one of your patients... they'll talk your ears off.