Pulmonary Capillary Wedge Pressure (PCWP) is measured from the distal port of a Swan-Ganz catheter during wedge inflation. What does PCWP primarily assess?

Pulmonary Capillary Wedge Pressure (PCWP) is measured from the distal port of a Swan-Ganz catheter during wedge inflation. What does PCWP primarily assess?

• A. The proximal port of a Swan-Ganz catheter during balloon inflation; assesses right atrial pressure.
• B. Distal port of a Swan-Ganz catheter during wedge inflation; assesses left-sided filling pressures.
• C. Peripheral IV line; measures systemic arterial pressure.
• D. Distal port of a Swan-Ganz catheter during measurement of pulmonary artery pressure only.

Answer: (B)

The key idea is that pulmonary capillary wedge pressure is a reflection of left-sided filling pressures, specifically the left atrial pressure and thus left ventricular preload. When the balloon on the Swan-Ganz catheter is inflated in a distal pulmonary artery segment, the distal port becomes wedged and the pressure is transmitted back from the pulmonary capillaries into the catheter. Because the balloon occludes forward flow, the pressure measured at the distal port equilibrates with the pressure on the left side of the heart, giving an estimate of left atrial pressure. This makes PCWP a surrogate for left-sided preload and filling pressures, useful for assessing volume status and helps in evaluating causes of pulmonary edema. The proximal port measures right atrial pressure, not PCWP, and peripheral IV lines do not provide PCWP. The wedge pressure is specifically the measurement taken during balloon-assisted wedge inflation to assess left-sided pressures, not general pulmonary artery pressure alone.

The key idea is that pulmonary capillary wedge pressure is a reflection of left-sided filling pressures, specifically the left atrial pressure and thus left ventricular preload. When the balloon on the Swan-Ganz catheter is inflated in a distal pulmonary artery segment, the distal port becomes wedged and the pressure is transmitted back from the pulmonary capillaries into the catheter. Because the balloon occludes forward flow, the pressure measured at the distal port equilibrates with the pressure on the left side of the heart, giving an estimate of left atrial pressure. This makes PCWP a surrogate for left-sided preload and filling pressures, useful for assessing volume status and helps in evaluating causes of pulmonary edema.

The proximal port measures right atrial pressure, not PCWP, and peripheral IV lines do not provide PCWP. The wedge pressure is specifically the measurement taken during balloon-assisted wedge inflation to assess left-sided pressures, not general pulmonary artery pressure alone.