Diffusion capacity

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In biology, diffusion capacity is a measurement of the lung's ability to absorb and excrete gases, notably, oxygen and carbon dioxide. It is part of a comprehensive test series of lung function called pulmonary function testing.

[edit] Calculation

The rate of flow is directly proportional to the oxygen gradient (per Fick's law of diffusion), and the diffusion capacity (DL) can be calculated as the ratio of oxygen flow over the oxygen gradient between the alveoli ("A") and the veins ("v"):

D_L = \frac {V^*_{O2}}{P_{AO2} - P_{vO2}}

(The asterisk should be read as a dot over the letter, which is used to denote rate in respiratory physiology.)

QUESTION: What do the above variables represent, specifically?

Because it can be difficult to measure these quantities, in Dlco, a small quantity of carbon monoxide is sometimes used, under the assummption that all the CO will bind, thus simplifying the equation:

D_L = \frac {V^*_{O2}}{P_{ACO2}}

[edit] External links

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