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Understanding ABGs - having trouble, any ideas?


I am doing an ICU rotation right now and so I need to be able to interpret ABGs. I'm not understanding them very well, and wondered if anybody knew of a "dumbed down" explanation anywhere? I am sure I'm just making it harder than it is, but I have patients to care for and tests to pass and I really do need to understand it!


Specializes in LTC/Peds/ICU/PACU/CDI. Has 24 years experience.

try this link future l&d nurse!

hope it helps ~ cheers :cheers: ,



Specializes in LTC/Peds/ICU/PACU/CDI. Has 24 years experience.

i also found this link that day to nite provided from a previous allnurses forum regarding abgs. you could also try this site as well.

cheers :cheers: ,


Conrad283, BSN, RN

Specializes in SICU, MICU, CICU, NeuroICU.

First you need the norms:

pH: 7.35 - 7.45

CO2: 35 - 45

HCO3: 22 - 26


pH: high CO2: norm HCO3: high - metabolic alkalosis

ex: 7.50|40|30

pH: low CO2: norm HCO3: low - metabolic acidosis

ex: 7.30|40|20

pH: high CO2: low HCO3: norm - respiratory alkalosis

ex: 7.47|30|24

pH: low CO2: high HCO3: norm - respiratory acidosis

ex: 7.27|50|23

Those are basic abg's if the world is all good. But in the case where it's not there are two situations that can occur.

Compensated ABG's are where the pH is NORMAL, but the CO2 and HCO3 are NOT normal.

1) You have to break the pH up 7.35 - 7.4 is acidotic, and 7.4 - 7.45 is alkaline.

2) Match the CO2 of HCO3 to the pH using the basics (above)

3) The fact that the other value is out of range makes it compensated.

ex: 7.43|30|20 - compensated respiratory alkalosis. etc

Then there's partial compensatory. I'm not very familiar with this, so I don't want to say the wrong thing

Hope this helps.

Daytonite, BSN, RN

Specializes in med/surg, telemetry, IV therapy, mgmt. Has 40 years experience.

this gets asked so much i can't believe we still haven't gotten all the links into a sticky thread that we can find yet!

go to these older threads for weblinks to sites that have abg tutorials and information on how to read and interpret abgs:

Thanks so much!! I am going to spend a lot of time on those links in the next few weeks, I bet. I don't think I've struggled with anything else as much as ABGs, so I will take all the help I can get. Thank you everyone!

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