Answer :
To estimate intrapulmonary shunt, blood gas samples from the pulmonary artery catheter are needed. The inferior vena cava and pulmonary artery carry deoxygenated blood, while the pulmonary vein and aorta carry oxygenated blood. Anatomical shunts in the lungs can cause mismatches between air ventilation and blood perfusion. Therefore, the correct answer is option d.
To estimate intrapulmonary shunt using the modified shunt equation, blood gas samples are needed from a pulmonary artery catheter, which provides the most accurate measure of the oxygen content in the blood that has not participated in gas exchange (deoxygenated blood). Other blood vessels, like the peripheral artery, central venous, and peripheral IV, do not provide blood samples that reflect the deoxygenated status necessary for calculating the intrapulmonary shunt.
Moreover, the anatomical structure of the circulatory system describes that blood in the inferior vena cava and the pulmonary artery is deoxygenated, while blood in the pulmonary vein and the aorta is oxygenated. This clarification helps us understand which blood vessels contain oxygen-rich and oxygen-poor blood, essential for understanding how shunts affect oxygenation.
Anatomical shunts, like the effect of gravity on the lungs, are regions where there's a mismatch between ventilation and blood perfusion, leading to reduced gas exchange efficiency. This concept is vital for understanding shunt physiology in the lung. Therefore, the correct answer is option d.
