ABG Value Question

Unless I'm missing something I think whatever answer key you are using is incorrect, this is leaning toward acidosis and should be metabolic acidosis. But they are correct that it is fully compensated, anytime the pH is normal and the CO2 and HCO3 are both abnormal that means that it is fully compensated.

It was a practice exam online, and have sent a note to the person running the page to get a better answer. Just wanted to try and get a different response as this was the question and answers with the one that they mentioned being the correct one.

12. Lab values: pH 7.39, paCo2 30, HCO3 19

A. metabolic alkalosis, fully compensated

B. metabolic alkalosis, partially compensated

C. respiratory acidosis, fully compensated

D. respiratory alkalosis, fully compensated

The answer is D: respiratory alkalosis, fully compensated

Yeah I still don't think this is accurate, at least not how I learned to interpret ABGs. When the pH is fully compensated you go with whether the value is closer to being acidosis or alkalosis and in this case it is closer to acidosis so it should be metabolic.

Thank you for the responses, much appreciated

At first I didn't see it, but now I think I can understand how it could be interpreted as compensated respiratory alkalosis.

The pH is so close to 7.4 that I wouln't really say that it leans acidotic or alkalotic; it's pretty 'middle of the road.' Your given CO2 and bicarb values could either be interpreted as compensated metabolic acidosis or compensated respiratory alkalosis, depending on your pH. If your CO2 and bicarb were unchanged, but your pH was 7.36, then I'd say it would definitely be compensated metabolic acidosis. However, if your CO2 and bicarb were unchanged, but your pH was 7.44, I'd definitely call it compensated respiratory alkalosis. With the information provided (pH of 7.39) it perhaps leans very slightly toward metabolic acidosis, but overall it's pretty ambiguous and could go either way.

Given your answer choices, compensated respiratory alkalosis is the best option (since compensated metabolic acidosis isn't an option).

The ambiguity makes it kind of a crappy question. If you had an actual patient with this gas, you'd have to look at the clinical factors to figure out which you're actually seeing (compensated metabolic acidosis, compensated respiratory alkalosis, or a little of both).

It's also a super weird example because the clinical presentation is so rare...I'm having trouble thinking of a circumstance where you'd have respiratory alkalosis for a long enough period of time that you'd see metabolic compensation...

As long as the pH is 7.35-7.45 it is considered "normal." Therefore, in this example, it's a normal pH, and is thus COMPENSATED.

It was a practice exam online, and have sent a note to the person running the page to get a better answer. Just wanted to try and get a different response as this was the question and answers with the one that they mentioned being the correct one.

12. Lab values: pH 7.39, paCo2 30, HCO3 19

A. metabolic alkalosis, fully compensated

B. metabolic alkalosis, partially compensated

C. respiratory acidosis, fully compensated

D. respiratory alkalosis, fully compensated

The answer is D: respiratory alkalosis, fully compensated

I'm going to agree with adventure_rn. Respiratory alkalosis, fully compensated is the only choice that fits with the lab values provided. It's compensated, because the pH is in the normal range of 7.35-7.45. It's definitely not a metabolic alkalosis, since your HCO3 is 19 and it's definitely not a respiratory acidosis since your CO2 is 30. If the answer key also had a choice for metabolic acidosis, fully compensated, I'd have chosen that.