What condition would most likely cause a high V/Q mismatch?

A high V/Q (ventilation-to-perfusion) mismatch occurs when there is an imbalance between the airflow (ventilation) reaching the alveoli and the blood flow (perfusion) in the surrounding capillaries. In the context of pulmonary embolism, this condition can cause a significant V/Q mismatch due to the obstruction of blood flow.

When a pulmonary embolism occurs, a clot (or other material) obstructs a pulmonary artery, reducing perfusion to the area of the lung supplied by that artery. If ventilation remains normal or is not significantly affected, there will be well-ventilated but poorly perfused areas of the lung. This leads to an increased ratio of ventilation to perfusion in those affected regions, resulting in a high V/Q ratio.

In contrast, pneumonia typically causes both ventilation and perfusion to be affected, as the infection leads to inflammation and consolidation in the lung, which stiffens lung tissue and may cause atelectasis or shunting, thereby resulting in a lower V/Q ratio in affected areas. Asthma primarily causes variable airflow obstruction and, while it can create some V/Q mismatch, it does not typically create high V/Q situations. Chronic bronchitis similarly causes airflow limitation but is characterized more by