COPD NCLEX Question [Walkthrough]

Nursing Knowledge

COPD NCLEX Question [Walkthrough]

COPD, a common, progressive lung disease, often leads to altered ABG values, indicating changes in oxygenation and carbon dioxide levels. Since understanding ABG results is so important for monitoring disease progression and therapeutic responses to COPD, being prepared for NCLEX questions on both COPD and ABG interpretation is essential. Practice with the full sample question walkthrough below!

Last updated: October 15, 2024

The nurse is assessing a client with COPD who has a pH of 7.32, a CO₂ of 46 mm Hg, and an HCO₃ of 28 mEq/L. Which condition does the nurse associate with these assessment findings?

Respiratory acidosis, partially compensated
Respiratory alkalosis, partially compensated
Metabolic acidosis, partially compensated
Metabolic alkalosis, partially compensated

#1 Analyze the question, cues, and numbers

What is normal, and what isn’t?

Tip: Whenever you have numerical values in a question stem, make a judgment: Is this high, low, or normal?

You are dealing with a client who has COPD, so they probably have respiratory problems.
A normal pH is 7.35 to 7.45, so the pH is lower than normal.
A CO₂ of 46 mm Hg is a little bit higher than normal (35 to 45).
A HCO₃ of 28 mEq/L is considered high, since normal would be 20–26.

The question stem gives us all the values we need for an ABG interpretation, which can result in the four different answers given as our answer choices.

Rephrase the question in your own words

“I am caring for a COPD patient with pH a little too low, CO₂ a little too high, and HCO₃too high. As answer choices, I have four descriptions of acid–base imbalances and need to interpret the values to decide which one describes the situation of this patient correctly.”

#2 Differentiate the answer options and eliminate based on the information in the stem

Tip: When all the answer choices look the same at first glance, make it easier for your brain by writing notes about each of them. Decipher what is the same and what is different.

Here, the four answer choices are simply the four different ways an acid–base imbalance can manifest itself: the combinations of acidosis vs alkalosis and respiratory vs metabolic. The task is to match up the values given for this patient with the correct imbalance.

Acidosis vs alkalosis

A pH is the value that determines if a patient is acidotic or alkalotic. So, judging this one already will eliminate 2 answer choices, since we have 2 that say acidosis and 2 that say alkalosis:

pH of 7.32 is not normal, but a little low.
It is considered acidotic.

So, we know the correct answer must be acidosis and can eliminate answer choices B and D based on the pH value given.

Respiratory acidosis, partially compensated
~~Respiratory alkalosis, partially compensated~~
Metabolic acidosis, partially compensated
~~Metabolic alkalosis, partially compensated~~

Respiratory acidosis vs metabolic acidosis

Having eliminated answers B and D, we know the client is in acidosis. The other values differentiate what causes the acidosis: Is it respiratory or metabolic?

CO₂ is considered an acid in the blood, and it is regulated by the lungs in the body. Respiratory acidosis means the acidosis is caused by elevated CO₂, which the client in the question does have.

Bicarbonate is considered a base, or alkalotic, which is regulated by the kidneys. Metabolic acidosis, with bicarbonate being a base, would have to be caused by less base, not more, but the HCO₃ level in this patient is elevated.

#3 Wrap-up

The low pH tells us the client is in acidosis, and the fact that CO₂ is elevated (→ more acid) and bicarbonate is not too low (→ enough base) tells us that the acidosis is respiratory. That makes answer A. “Respiratory acidosis, partially compensated” the correct answer.

The elevated HCO₃ value is the body (kidneys) trying to compensate for the acidosis (→ trying to raise alkalotic levels). Since the pH is not quite back to normal, the acidosis is partially compensated.

Recap: COPD and acid–base imbalances

COPD in a nutshell

Chronic obstructive pulmonary disease (COPD) is a chronic, progressive lung disease that involves airway impairment and causes increasing difficulty with breathing. Diagnosis is based on symptom history and pulmonary function tests, while a chest X-ray can rule out other diseases and identify complications.

ABGs will show lower CO₂ and rising CO₂ depending on the exacerbation and progression of the disease.

Acid–base balance and ABG interpretation

ABG interpretation refers to the interpretation of arterial blood gases. If pH, CO₂, and HCO₃ values are in a normal range, the body is in homeostasis. If the values are outside of the normal range, the body is experiencing an acid–base imbalance. There are four variations of acid–base imbalances, depending on which of the values are too high or too low:

Respiratory acidosis
Metabolic acidosis
Respiratory alkalosis
Metabolic alkalosis

Take Lecturio’s online video course on interpreting ABG values here →