What are the carbon dioxide and oxygen levels in the superior vena cava?

The superior vena cava carries deoxygenated blood from the upper body to the right atrium of the heart. As a result, it has higher levels of carbon dioxide and lower levels of oxygen compared to oxygenated blood in the pulmonary veins. Typically, the carbon dioxide concentration in the superior vena cava is elevated due to cellular metabolism, while oxygen levels are relatively low, reflecting the blood's return from systemic circulation.