Progressive Care Nursing Certification (PCCN) Practice Exam

In which scenario would a rise in PaCO2 occur?

1. Good alveolar ventilation

2. Decreased tidal volume

3. Effective gas exchange

4. Pulmonary edema

The correct answer is: Decreased tidal volume

A rise in PaCO2 indicates that there is an accumulation of carbon dioxide in the blood, often due to hypoventilation or inadequate elimination of CO2 from the body. In a scenario with decreased tidal volume, the amount of air exchanged during each breath is reduced. This decreased lung ventilation can lead to insufficient removal of CO2 from the bloodstream, resulting in elevated levels of carbon dioxide and a subsequent increase in PaCO2. In scenarios with good alveolar ventilation or effective gas exchange, the body effectively removes CO2, preventing its accumulation. Similarly, while pulmonary edema can affect gas exchange, the scenario focuses on decreased tidal volume as a more direct cause for an increase in PaCO2. This understanding is crucial in clinical settings, as recognizing the cause of elevated PaCO2 assists in determining appropriate interventions to improve ventilation and gas exchange.