Which value best describes a normal SvO2 range?

• A. 60-65%
• B. 70-75%
• C. 80-85%
• D. 50-60%

Answer: (B)

Normal mixed venous oxygen saturation (SvO2) reflects the balance between oxygen delivery and tissue oxygen demand. In healthy conditions, SvO2 is typically in the mid-60s up to about 75% (often cited as 65-75%, with some sources extending toward 80%). The range around 70-75% best represents the typical normal value, aligning with the common clinical reference for a balanced delivery and consumption of oxygen.

SvO2 is measured in the pulmonary artery and depends on several factors: cardiac output, hemoglobin level and its oxygen-carrying capacity, arterial oxygen content, and the tissues’ rate of oxygen use. If SvO2 drops, it suggests higher tissue extraction due to reduced delivery or increased consumption. If SvO2 rises, it can indicate reduced extraction or an excess of delivery relative to consumption.