AEMCA Practice Exam

What is a physiological shunt related to V/Q mismatch?

1. Blood does not circulate in the lungs at all

2. Air entry to the lung is obstructed while blood profuses

3. Both blood and air are obstructed

4. Normal ventilation and perfusion

The correct answer is: Air entry to the lung is obstructed while blood profuses

A physiological shunt refers to a situation where blood passes through the lungs but does not get oxygenated due to obstructed airflow. In the context of ventilation/perfusion (V/Q) mismatch, this means that although there is adequate blood flow (perfusion) to specific areas of the lung, the corresponding air entry (ventilation) is impaired, preventing effective gas exchange. Therefore, the blood that circulates through those ventilatory-deficient regions does not receive the oxygen it needs, leading to a decrease in overall oxygenation in the bloodstream. This is why the second option is accurate, as it highlights the obstruction of air entry while blood continues to flow through the lung, confirming the scenario of a physiological shunt in the context of V/Q mismatch.