There are 2 types of mismatch: dead space and shunt. Alveolar gas exchange depends not only on ventilation of the alveoli but also on circulation of blood through the alveolar capillaries. This makes sense. You need both oxygen in the alveoli, and adequate blood flow past alveoli to pick up oxygen, other wise oxygen cannot be delivered.

When the proper balance is lost between ventilated alveoli and good blood flow through the lungs, ventilation/perfusion mismatch is said to exist. The ventilation/perfusion ratio is often abbreviated V/Q. V/Q mismatch is common and often effects our patient’s ventilation and oxygenation. Read More …