A V/Q mismatch resulting in infinity indicates which condition?

A V/Q mismatch that results in infinity indicates a situation where there is normal ventilation but no perfusion. In such a scenario, the alveolar units are receiving air but the blood flow to those alveoli is absent, effectively creating a situation where the ventilation is maximized while the perfusion remains zero. This scenario typically reflects conditions like a pulmonary embolism, where the blockage prevents blood from reaching certain areas of the lung, leading to inadequate gas exchange despite the presence of air in the alveoli.

The concept of V/Q ratio, which compares the amount of air reaching the alveoli to the amount of blood reaching the alveoli, becomes crucial here. When perfusion is absent, even though there is adequate airflow, the V/Q ratio becomes undefined or infinite, as division by zero occurs in the calculation of V/Q. This helps in understanding why having normal ventilation without perfusion creates such a drastic mismatch that is critical in diagnosing the underlying pathology.