Ventilation-Perfusion Matching Lab

Presets

Overall readouts

Total ventilation

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Total perfusion

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Gas-exchange efficiency

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Totals unchanged from last preset — watch efficiency move on its own.

Alveolar regions

Why totals aren't enough

Each alveolar region needs fresh air (ventilation, blue) and blood flow (perfusion, red) arriving together to exchange oxygen and CO₂. A region's local efficiency here is modelled as 2·min(V,Q)/(V+Q) — 100% when V and Q are equal, however large or small; it collapses toward 0% when one badly outstrips the other, because the surplus (extra air with no blood to carry it, or extra blood with no air to load) is wasted.

Well-matched — every region gets a similar split of the same total air and blood → most flow is usefully paired → high overall efficiency.
Mismatched — identical grand totals, but redistributed so some regions are ventilation-heavy/perfusion-poor and others the reverse → far less flow is paired at the same location → efficiency drops sharply even though nothing about the totals changed.

This is the core clinical idea behind ventilation-perfusion (V/Q) mismatch: a pulmonary embolism, mucus plug or collapsed airway doesn't have to change how much air or blood the lung handles in aggregate to still cripple oxygenation — it only has to break the local pairing.

Air flow (ventilation) Blood flow, deoxygenated Blood flow, oxygenated

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