diffusing capacity

dif·fus·ing capacity (d-fyzng)

n.

The capacity of the alveolocapillary membrane to transfer gas.

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diffusing capacity

[difyo̅o̅′sing]

the rate of gas transfer through a unit area of a permeable membrane per unit of gas pressure difference across it. It is affected by specific chemical reactions that may occur in the blood. Also called diffusion factor, transfer factor of lungs.

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diffusing capacity [dĭ-fuz´ing]

the rate at which a gas diffuses across the alveolocapillary membrane per unit difference in the partial pressure of the gas across the membrane, expressed in ml/min/mm Hg. Because of their high affinity for hemoglobin, both oxygen and carbon monoxide are limited in their rate of diffusion by their diffusing capacity. The diffusing capacity of the lung for these gases is symbolized by Dl_O2 and Dl_CO. The parameter usually measured is Dl_CO. The normal value for the diffusing capacity of oxygen is 20 ml/min/mm Hg. If, during quiet breathing, the pressure difference of oxygen averages 11 mm Hg, a total of approximately 220 ml of oxygen diffuses through the respiratory membrane each minute. During strenuous exercise or other conditions that increase pulmonary activity, the diffusing capacity may increase to three times as much as that during rest. Pulmonary diseases that damage the respiratory membrane greatly interfere with the capacity of the oxygen to pass through the membrane and oxygenate the blood.

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diffusing capacity

the rate at which a gas diffuses across the alveolar-capillary membrane per unit difference in the partial pressure of the gas across the membrane, expressed in ml/min/mmHg. Because of their high affinity for hemoglobin both oxygen and carbon monoxide are limited in their rate of diffusion by their diffusing capacity.

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diffusing capacity

Pulmonary medicine A measure of a substance's efficiency in transversing a particular barrier, which in the lungs corresponds to the ability of gases in the alveolar space to enter the blood, and of the gases in the blood to enter the alveoli for removal from the body by exhalation. See Pulmonary function test.