What is normal Qs/Qt?

What is normal Qs/Qt?

• A. Less than 5
• B. 5-10
• C. Greater than 10
• D. About 5

Answer: (A)

Qs/Qt is the shunt fraction—the portion of pulmonary blood flow that bypasses gas exchange. In a healthy neonate, this physiologic shunt is very small, normally less than 5% of the total cardiac output. Think of it as the small amount of blood that still passes through the lungs without picking up oxygen due to normal anatomic shunts, which is why most blood gets oxygenated. When Qs/Qt remains under 5%, oxygenation is typically adequate. If it rises above that threshold, it indicates some alveoli aren’t contributing to gas exchange, which can occur with conditions causing V/Q mismatch or true shunt.

Qs/Qt is the shunt fraction—the portion of pulmonary blood flow that bypasses gas exchange. In a healthy neonate, this physiologic shunt is very small, normally less than 5% of the total cardiac output. Think of it as the small amount of blood that still passes through the lungs without picking up oxygen due to normal anatomic shunts, which is why most blood gets oxygenated. When Qs/Qt remains under 5%, oxygenation is typically adequate. If it rises above that threshold, it indicates some alveoli aren’t contributing to gas exchange, which can occur with conditions causing V/Q mismatch or true shunt.