What is the normal oxygen saturation value associated with the Pulmonary Capillary Wedge pressure (PCWP) region?

• A. 85%
• B. 90%
• C. 92%
• D. 88%

Answer: (B)

The key idea is that the blood sampled from the pulmonary capillary wedge region represents left atrial (and thus systemic arterial) blood oxygen content. When a Swan-Ganz catheter is wedged, it traps blood from the pulmonary capillaries as it drains into the left atrium, so the oxygen saturation there is very high, reflecting left-sided oxygenation.

In practice, the normal value cited for oxygen saturation in this wedge region is about 90%. That’s because, while it mirrors arterial oxygen content, it isn’t a perfect arterial sample and can be affected by minor admixture and measurement variation. So 90% is the best match among the options for a normal wedge-region oxygen saturation.