These can occur because of an obstruction in the airway, like a mucous plug, a peanut, or a tumor (cannot ventilate distal to the mucus plug) or more distal at the level of alveoli, from edema/blood/pus in an alveolus (cannot get air/oxygen to the alveoli/capillary interface), or a collapsed airway.

There is no ventilation no air is moving in and out of alveoli. Let’s start with extremes which will best illustrate the example: V/Q Mismatch vs. Pathological conditions create extreme amounts of V/Q mismatching which are not consistent with proper oxygenation. At the lung bases, there’s more ventilation, but much more blood flow, so VQ, and the V/Q ratio is high. There will always be some element of “mismatch” between blood flow and ventilation as one moves through different lung zones, but this is normal physiology and consistent with normal oxygenation. Now that groundwork is laid, let us investigate the concept of a mismatch between these two forces that we strive to keep in balance. This is blood flowing through the pulmonary arteries into pulmonary capillaries, and ultimately pouring out the pulmonary veins back into the left atrium.Īlong the way, as long as it’s passing by alveoli that are full of oxygen, and that oxygen can diffuse across pneumocytes into the blood, this blood will pick up some oxygen in the pulmonary capillaries, and drop off some CO2. What does the ‘Q’ in “VQ Mismatch” stand for?īlood flow. Also keeps us going. For our intents and purposes, this is air/oxygen moving in and out of the lungs. What does the ‘V’ in “VQ Mismatch” stand for?

Let’s investigate what this really means so that when you drop knowledge bombs like this in front of your residents and attendings, you have some data and understanding to back it up. It sounds smart because it is, and there’s a very good chance that a ventilation perfusion (VQ) mismatch is why your patient is hypoxic. Brilliant medical student, AM Rounds, c. “.and s/he is probably suffering from some element of a V/Q mismatch.”

Mismatch vs. shunt vs. dead space