AEMCA Practice Exam

What does an anatomical shunt indicate in terms of V/Q mismatch?

1. Blood profusing the lung but obstructing air entry

2. Blood that does not profuse the lung, bypassing it

3. Normal blood and air circulation

4. Air entering the lungs without profusion

The correct answer is: Blood that does not profuse the lung, bypassing it

An anatomical shunt specifically refers to blood flow that bypasses the lungs entirely, meaning it does not participate in gas exchange. In terms of ventilation-perfusion (V/Q) mismatch, an anatomical shunt occurs when there are physiological pathways allowing blood to flow from the right side of the heart to the left without being oxygenated in the lungs first. This can happen due to congenital heart defects, for example, where blood flows through a defect in the wall separating the atria or ventricles. In this scenario, the mismatch arises because while blood is still moving through the circulatory system, it does not get the necessary oxygenation, leading to a lack of adequate oxygen supply to the body's tissues. Thus, recognizing an anatomical shunt as blood that bypasses the lungs is crucial for understanding how it contributes to V/Q mismatch and overall impaired oxygen delivery. The other options reference various respiratory and circulatory issues but don't accurately depict the mechanism of an anatomical shunt.