What pressure is obtained distal to the balloon wedge?

• A. Right atrial pressure
• B. Pulmonary artery pressure
• C. Left atrial pressure
• D. Aortic pressure

Answer: (C)

When the balloon on the pulmonary artery catheter is inflated and the catheter wedges in a distal branch, forward flow is stopped and the pressure beyond the balloon equilibrates with the pressure in the left atrium through the pulmonary veins. That distal, or wedge, pressure thus serves as an indirect estimate of left atrial pressure. This is known as the pulmonary capillary wedge pressure and is used to assess left-sided preload and filling pressures. It is not measuring right atrial pressure, pulmonary arterial pressure, or aortic pressure.