This is an NCLEX practice question on partially compensated vs fully compensated ABGs. This question provides a scenario about arterial blood gas results. As the nurse, you must determine if this is a respiratory or metabolic problem, alkalosis or acidosis along with if it is uncompensated, partially or fully compensated based on the results.
This question is one of the many questions we will be practicing in our new series called “Weekly NCLEX Question”.
So, every week be sure to tune into our YouTube Channel for the NCLEX Question of the Week.
To solve ABGs problems, I like to use the Tic Tac Toe method. If you are not familiar with this method, please watch my video on how to solve arterial blood gas problems with this method.
The Tic Tac Toe method makes solving ABG problems so EASY. However, if the ABG values are partially or fully compensated you must take it a step further by analyzing the values further with this method, which is the purpose of this review. My goal is to show you how to use the Tic Tac Toe method for partially and fully compensated interpretation.
So let’s begin:
NCLEX Practice Questions on Partially vs. Fully Compensated ABGs
A patient has the following arterial blood gas results: blood pH 7.43, PaCO2 28 mmHg, and HCO3 18 mEq/L. This is known as:
A. Partially compensated respiratory alkalosis
B. Fully compensated metabolic acidosis
C. Partially compensated respiratory acidosis
D. Fully compensated respiratory alkalosis
The first thing you want to do is to pull from your memory bank the normal values for arterial blood gases.
Here they are:
pH: 7.35-7.45 (less than 7.35 ACID & greater than 7.45 ALKALOTIC)
PaCO2: 45-35 (greater than 45 ACID & less than 35 ALKALOTIC)**
HCO3: 22-26 (less than 22 ACID & greater than 26 ALKALOTIC)
**PaCO2 values are the opposite…so remember that
Then ask yourself the following questions to help you start interpreting the values….
Question 1: Is this a respiratory or metabolic problem?
- PaCO2 represents a RESPIRATORY problem
- HCO3 represents a METABOLIC problem
Question 2: Is this acidosis or alkalosis?
- Remember the normal values for acid vs alkalotic
Question 3: Is it uncompensated, partially, or fully compensated?
- Look at the pH: is it normal or abnormal?
- If the pH is ABNORMAL: it is either uncompensated or partially compensated…it will NEVER be fully compensated
- If the pH is NORMAL: it is fully compensated because the body has corrected the problem
Now set-up the problem using the Tic Tac Toe method:
pH: 7.43 (falls within 7.35-7.45) = NORMAL
PaCO2: 28 (less than 35) = ALKALOTIC
HCO3: 18 (less than 22) = ACIDIC
So, we don’t have a tic tac toe, therefore, the values are representing compensation (either partially or fully).
To determine the type of compensation look at the pH…is it normal or abnormal? It’s NORMAL! Therefore, it is fully compensated.
BUT is this a respiratory or metabolic problem (this is where students have trouble)?
To determine this, look at the PaCO2 and HCO3 and ask yourself which value deviates the MOST from its normal value?
PaCO2: 28…normal is 35. It deviates 7 points from normal (35-28 = 7).
HCO3: 18…normal is 22. It deviates 4 points from normal (22-18 = 4).
So, it is a respiratory problem (remember PaCO2 represents respiratory), and according to our tic tac toe above it is respiratory alkalosis, fully compensated by the means of metabolic acidosis.
Remember we learned from our acid-base imbalance series that when the body enters into respiratory alkalosis it will try to COMPENSATE/CORRECT the body by making the metabolic system keep acids within the kidneys. This will hopefully bring down the blood pH level since the conditions are so alkalotic.
Answer is: D
A patient has the following arterial blood gas results: blood pH 7.50, PaCO2 49, and HCO3 30 mEq/L. This is known as:
A. Fully compensated respiratory acidosis
B. Partially compensated metabolic alkalosis
C. Partially compensated metabolic acidosis
D. Fully compensated metabolic alkalosis
Again pull from your memory bank regarding normal values for ABGs as we did in the previous problem and set-up the problem using the Tic Tac Toe method:
pH: 7.50 (greater than 7.50) = Abnormal…ALKALOTIC
PaCO2: 49 (greater than 45) = ACIDIC
HCO3: 30 (greater than 26) = ALKALOTIC
There is a tic tac present: there is a three in a row with base, pH, HCO3.
We can see that this is a metabolic problem due to alkalosis. But now we must determine if this is uncompensated, partially, or fully compensated?
The pH is abnormal and this rules out full compensation, but is it uncompensated or partial?
To answer this you must look at the system that will attempt to correct the metabolic alkalosis, which would be the respiratory system, hence the PaCO2.
It is normal or abnormal? It is abnormal! Therefore, it is trying to correct the metabolic alkalosis that is presenting but it is unable to because the pH is still abnormal. If the pH was normal then full compensation has occurred.
Now you may be asking yourself what if the PaCO2 was normal? Then it would be uncompensated because the respiratory system isn’t attempting to correct the metabolic alkalosis.
Answer is: B