Progressive Care Nursing Certification (PCCN) Practice Exam

Which ABG change is expected in a patient experiencing respiratory alkalosis?

1. Increased pH and decreased pCO2

2. Decreased pH and increased pCO2

3. Increased pH and increased O2 saturation

4. Decreased pH and normal HCO3

The correct answer is: Increased pH and decreased pCO2

In respiratory alkalosis, the primary physiological change involves a decrease in carbon dioxide (pCO2) levels due to hyperventilation or other factors that lead to excessive respiratory loss of CO2. As CO2 levels drop, this results in an increase in blood pH, thus causing an alkaline state. When evaluating the expected arterial blood gas (ABG) changes in this condition, it is crucial to note that a higher pH indicates alkalinity, and the reduced pCO2 corresponds to the hyperventilation seen in respiratory alkalosis. Therefore, the presence of increased pH along with decreased pCO2 accurately reflects the state of respiratory alkalosis. Regarding the other options, the second choice indicating a decreased pH and increased pCO2 characterizes respiratory acidosis, not alkalosis. The third option notes that both pH and O2 saturation increase, but while the pH does increase in respiratory alkalosis, O2 saturation is not typically directly affected in this disorder. Additionally, the last option reflects a decreased pH, which aligns with a different acid-base disturbance, likely metabolic acidosis, rather than respiratory alkalosis. Thus, the first option presents the proper relationship between these variables in the context of respiratory alkalosis.