Neonatal Nurse Practitioner Practice Exam

During respiratory alkalosis, which changes are expected in CO2 and HCO3 levels?

1. Increase in both CO2 and HCO3

2. Decrease in CO2 and HCO3

3. Increase in CO2 and decrease in HCO3

4. Decrease in CO2 and increase in HCO3

The correct answer is: Decrease in CO2 and increase in HCO3

In respiratory alkalosis, the primary disturbance is a decrease in carbon dioxide (CO2) levels in the blood due to hyperventilation. This decrease in CO2 leads to a resultant increase in blood pH, causing an alkalotic state. When CO2 levels drop, there is less carbonic acid formed in the body, since carbonic acid is created when CO2 dissolves in water. As a result, the bicarbonate (HCO3) levels can also be affected. In pure respiratory alkalosis, it is common for the body to adjust over time, leading to a slight decrease in HCO3 as the kidneys compensate by excreting bicarbonate to help restore balance. However, in acute respiratory alkalosis, the primary and immediate change is the decrease in CO2. This response allows the blood pH to gradually move back towards a more normal level, as the system aims to correct itself. Thus, during an episode of respiratory alkalosis, one would expect to see a decrease in CO2 levels as the hallmark change, accompanied by a possible decrease in bicarbonate over time as part of the compensatory mechanism.