Arterial Blood Gas (ABG) Interpretation: Practice Problems, Answers, & Cheatsheet

by Cathy Parkes July 17, 2020 Updated: January 18, 2023 2 min read 6 Comments

Review ABG Interpretation with Cathy!

Value	Normal Range	Abnormal Values
pH	7.35-7.45	pH < 7.35 indicates ACIDOSIS (ACID) ph > 7.45 indicates ALKALOSIS (BASE)
PaCO2(Respiratory System)	35-45	PaCO2 < 35 indicates ALKALOSIS (BASE) PaCO2 > 45 indicates ACIDOSIS (ACID)
HCO3(Metabolic System)	22-26	HCO3 < 22 indicates ACIDOSIS (ACID) HCO3 > 26 indicates ALKALOSIS (BASE)

If pH, PaCO2 and HCO3 are all in NORMAL range, we have HOMEOSTASIS!

With ABG interpretation problems, we are trying to figure out 3 things:

Is acidosis or alkalosis present (based on pH)?
If acidosis or alkalosis is present, which system is to blame: Respiratory system (PaCO2) or Metabolic system (HCO3)?
- Who is acting up?
Is compensation occurring? If so, is the acid/base imbalance partially or fully compensated?
- If the Respiratory system is acting up, is the Metabolic system trying to fix the situation?
- If the Metabolic system is acting up, is the Respiratory system trying to fix the situation?

Acid/Base Imbalance

Respiratory Acidosis

Learn more in our article on respiratory acidosis.

pH	PaCO2	HCO3	Interpretation
Acid	Acid	Normal	Uncompensated respiratory acidosis.(Respiratory system is acting up, Metabolic system is NOT trying to fix the situation).
Acid	Acid	Base	Partially compensated respiratory acidosis.(Respiratory system is acting up, Metabolic system is TRYING to fix the situation).
Normal (but closer to acidic)	Acid	Base	Fully compensated respiratory acidosis.(Respiratory system is acting up, Metabolic system has FIXED the situation).

Respiratory Alkalosis

pH	PaCO2	HCO3	Interpretation
Base	Base	Normal	Uncompensated respiratory alkalosis.(Respiratory system is acting up, Metabolic system is NOT trying to fix the situation).
Base	Base	Acid	Partially compensated respiratory alkalosis.(Respiratory system is acting up, Metabolic system is TRYING to fix the situation).
Normal (but closer to basic)	Base	Acid	Fully compensated respiratory alkalosis.(Respiratory system is acting up, Metabolic system has FIXED the situation).

Metabolic Acidosis

pH	PaCO2	HCO3	Interpretation
Acid	Normal	Acid	Uncompensated metabolic acidosis.(Metabolic system is acting up, Respiratory system is NOT trying to fix the situation).
Acid	Base	Acid	Partially compensated metabolic acidosis.(Metabolic system is acting up, Respiratory system is TRYING to fix the situation).
Normal (but closer to acidic)	Base	Acid	Fully compensated metabolic acidosis.(Metabolic system is acting up, Respiratory system has FIXED the situation).

Metabolic Alkalosis

pH	PaCO2	HCO3	Interpretation
Base	Normal	Base	Uncompensated metabolic alkalosis.(Metabolic system is acting up, Respiratory system is NOT trying to fix the situation).
Base	Acid	Base	Partially compensated metabolic alkalosis.(Metabolic system is acting up, Respiratory system is TRYING to fix the situation).
Normal (but closer to basic)	Acid	Base	Fully compensated metabolic alkalosis.(Metabolic system is acting up, Respiratory system has FIXED the situation).

Cathy Parkes

6 Responses

Kate

June 01, 2023

chef’s kiss these videos made this topic easy to comprehend! Thank you!!

Daniella

December 22, 2021

Thank you for letteing me understand. I really appreciate it

Ada

October 06, 2021

Thanks so much, your ABG interpretations help me a lot get clarifications on things that were confusing to me before. I appreciate you taking your time to do it. God bless.

Christina

May 05, 2021

Thanks for the video & cheat sheet! They are so helpful for my coming up exam.

Katie

December 17, 2020

Wow! I was very confused about ABGs before this video and now I completely understand them! Thank you so much for keeping it short and simple.

Issy

September 16, 2020

This video is a blessing to me. It is short and straight to the point. very easy to understand.

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ABG Interpretation, part 7: Metabolic Alkalosis

by Cathy Parkes June 22, 2021 4 min read

ABG results for: Uncompensated Metabolic Alkalosis, Partially compensated Metabolic Alkalosis, and Fully compensated Metabolic Alkalosis. Plus, learn the causes, symptoms, and treatment of Metabolic Alkalosis.

ABG Interpretation, part 6: Metabolic Acidosis

by Cathy Parkes June 17, 2021 6 min read

ABG results for: Uncompensated Metabolic Acidosis, Partially compensated Metabolic Acidosis, and Fully compensated Metabolic Acidosis. Plus the causes, symptoms, and treatment of Metabolic Acidosis.

ABG Interpretation, part 5: Respiratory Alkalosis

by Cathy Parkes June 15, 2021 4 min read 1 Comment

ABG results for: Uncompensated Respiratory Alkalosis, Partially compensated Respiratory Alkalosis, and Fully compensated Respiratory Alkalosis. Plus, learn the causes, symptoms, and treatment of Respiratory Alkalosis.