Progressive Care Nursing Certification (PCCN) Practice Exam

What is the primary cause of hypocarbia in a patient with a pulmonary embolism?

1. Increased respiratory rate

2. Reduced pulmonary perfusion

3. Hypoxemia from low oxygen levels

4. Acute right ventricular failure

The correct answer is: Increased respiratory rate

In the context of a pulmonary embolism, hypocarbia, or decreased carbon dioxide levels in the blood, is primarily caused by an increased respiratory rate. When a patient experiences a pulmonary embolism, the body reacts by hyperventilating, which is an attempt to compensate for decreased oxygenation and to manage the perception of respiratory distress. This hyperventilation leads to increased exhalation of carbon dioxide, resulting in hypocarbia. While reduced pulmonary perfusion does occur with a pulmonary embolism, it is not the direct mechanism leading to hypocarbia. Similarly, while hypoxemia and acute right ventricular failure may contribute to the patient's overall condition, they are not the primary drivers of decreased CO2 levels. The primary physiological response to the stress of the embolism and the subsequent hypoxia is an increase in respiratory effort to enhance oxygen intake and eliminate CO2, leading to the observed hypocarbia.