Certified Registered Nurse Anesthetist (CRNA) Practice Exam

What is the definition of pulmonary vascular resistance?

1. Flow of blood through left atrium

2. Resistance to blood flow out of the right ventricle

3. Pressure generated by the left ventricle

4. Resistance to blood returning to the heart

The correct answer is: Resistance to blood flow out of the right ventricle

Pulmonary vascular resistance is defined as the resistance that the right ventricle must overcome to pump blood into the pulmonary circulation. This primarily takes into account the pressure required to push blood through the pulmonary arteries and into the lungs, where gas exchange occurs. The higher the resistance in these vessels, the harder the right ventricle has to work to achieve adequate blood flow, which can have significant implications for cardiac output and overall cardiovascular function. The other options do not encapsulate the essence of pulmonary vascular resistance. The flow of blood through the left atrium pertains to the left side of the heart and is more related to systemic circulation. Pressure generated by the left ventricle reflects systemic vascular resistance and overall cardiac output but does not specifically measure resistance in the pulmonary circuit. Resistance to blood returning to the heart generally addresses venous return and is not focused on the pressures or performance of the right ventricle in relation to the pulmonary circulation.