AEMCA Practice Exam

What is mainly altered in a condition with a low V/Q ratio?

1. Oxygen levels and carbon dioxide elimination

2. Blood flow within the network of the lungs

3. Overall lung volume and capacity

4. Airway resistance only

The correct answer is: Oxygen levels and carbon dioxide elimination

In conditions characterized by a low ventilation-to-perfusion (V/Q) ratio, the primary alteration is in the oxygen levels and the elimination of carbon dioxide. A low V/Q ratio typically indicates that there is insufficient ventilation relative to blood flow in the lungs. This imbalance means that while the perfusion of blood is adequate, the oxygen supply from the air in the alveoli is reduced. As a result, the oxygen levels in the blood may decrease, leading to hypoxemia (low oxygen saturation). Simultaneously, the excess carbon dioxide produced by the cells is not effectively eliminated due to the inadequate ventilation. This can lead to respiratory acidosis as CO2 accumulates in the bloodstream. In contrast, alterations in blood flow, lung volume and capacity, or airway resistance are not the primary concerns when discussing a low V/Q ratio. While blood flow may still be present, it is the impaired gas exchange due to reduced ventilation that primarily affects oxygen and carbon dioxide levels in the bloodstream.