Which statement about pulmonary artery pressure is true?

• A. It is lower than systemic arterial pressure
• B. It is higher than systemic arterial pressure
• C. It is the same as systemic arterial pressure
• D. It is unaffected by cardiac output

Answer: (A)

Pulmonary circulation is a low‑resistance, low‑pressure system. The right ventricle pumps blood into the pulmonary arteries and the capillary bed of the lungs where vascular resistance is much lower than in the systemic circulation. Because of this setup, the mean pressure in the pulmonary artery is substantially lower than systemic arterial pressure—for example, roughly 12–16 mmHg on average in the pulmonary circuit versus about 90–100 mmHg mean in the systemic arteries.

So the true statement is that pulmonary artery pressure is lower than systemic arterial pressure. It’s not higher, not the same, and it can be influenced by cardiac output—the more blood the heart pumps, the more flow through the lungs and, modestly, the higher the pulmonary arterial pressure tends to be, though the system’s low resistance keeps it well below systemic pressures.