Progressive Care Nursing Certification (PCCN) Practice Exam

A patient with COPD has a PaCO2 of 65 and a pH of 7.30. Which condition does this indicate?

1. Respiratory alkalosis

2. Respiratory acidosis

3. Metabolic alkalosis

4. Metabolic acidosis

The correct answer is: Respiratory acidosis

The patient's arterial blood gas values indicate a condition of respiratory acidosis. In interpreting the provided values, a PaCO2 of 65 mmHg signifies hypercapnia, indicating an elevated level of carbon dioxide in the blood, typically associated with hypoventilation or inadequate respiratory function. The pH of 7.30 is lower than the normal range (7.35-7.45), indicating acidemia. In respiratory acidosis, the body fails to adequately eliminate carbon dioxide, causing an increase in hydrogen ions, which lowers the pH. This combination of an elevated PaCO2 and a decreased pH confirms that the patient is experiencing respiratory acidosis. Additionally, in cases like COPD, the underlying lung disease often leads to chronic retention of CO2, reinforcing the diagnosis. In contrast, respiratory alkalosis would present with a high pH and low PaCO2, metabolic acidosis would have a low pH with a normal or low PaCO2 due to compensatory respiratory hyperventilation, and metabolic alkalosis would show a high pH despite PaCO2 levels. Given the patient's specific values, the clear indication of respiratory acidosis is evident.