Ventilation-perfusion mismatch (V/Q mismatch)
Ventilation (V) means the process that air flows into and flows out of the alveoli. Perfusion (Q) means that the blood flows to alveolar capillaries. To make sure a successful gas exchange, the rates of ventilation and perfusion must be equal. Ventilation-perfusion mismatch happens when one or more areas of the lungs receive oxygen with no blood flow or have blood flow with no oxygen. For instance, an obstruction in the airway, like when you are choking, or obstruction in blood vessels, like when you have a blood clot, can lead to a ventilation-perfusion mismatch.
