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NCLEX QUESTION TYPE TUTORIAL
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?
Tip: Whenever you have numerical values in a question stem, make a judgment: Is this high, low, or normal?
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.
“I am caring for a COPD patient with pH a little too low, CO2 a little too high, and HCO3 too 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.”
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.
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:
So, we know the correct answer must be acidosis and can eliminate answer choices B and D based on the pH value given.
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.
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.
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.
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:
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