Certified Post Anesthesia Nurse (CPAN) Practice Exam

What type of acidosis is expected in a patient with ABG results indicating pH = 7.24 and PCO2 = 56?

1. Respiratory acidosis

2. Metabolic acidosis

3. Respiratory alkalosis

4. Metabolic and respiratory acidosis

The correct answer is: Respiratory acidosis

In analyzing the provided arterial blood gas (ABG) results, a pH of 7.24 indicates acidemia, as normal pH values range from 7.35 to 7.45. The PCO2 value of 56 is elevated, as normal range for PCO2 is typically 35 to 45 mmHg. In respiratory acidosis, the primary problem is an increase in PCO2 due to inadequate ventilation, leading to a corresponding decrease in pH. The elevated PCO2 in this case is a clear indicator that the body is retaining carbon dioxide, which results in an accumulation of carbonic acid, thereby lowering the pH. This situation directly correlates with respiratory acidosis, where the respiratory system fails to eliminate CO2 effectively, resulting in an increased concentration in the blood and a subsequent drop in pH. The other options can be ruled out because metabolic acidosis would be indicated by a low pH and a normal or low PCO2 (the body compensates by hyperventilating to reduce CO2). Respiratory alkalosis would show a high pH and low PCO2, and the combination of metabolic and respiratory acidosis would indicate both high PCO2 and