diffusing capacity

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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 DlO2 and DlCO. The parameter usually measured is DlCO. 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.

dif·fus·ing ca·pac·i·ty

(symbol, D, followed by subscripts indicating location and chemical species),
the amount of oxygen taken up by pulmonary capillary blood per minute per unit average oxygen pressure gradient between alveolar gas and pulmonary capillary blood; units are: ml/min/mm Hg; also applied to other gases such as carbon monoxide, which is used in the standard clinical measure of diffusing capacity.

diffusing capacity (D)

[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.

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.

dif·fus·ing ca·pa·ci·ty

(di-fyūz'ing kă-pas'i-tē)
The amount of oxygen taken up by pulmonary capillary blood per minute per unit average oxygen pressure gradient between alveolar gas and pulmonary capillary blood; units are: mL/min/mmHg; also applied to other gases such as carbon monoxide.

diffusing capacity

of the lungs: the volume of a gas that moves across from the alveoli into the blood per minute, per unit partial pressure difference for that gas over the lungs as a whole. Depends, for any gas, on the total area and average thickness of the alveolar-capillary interface. Of most interest for oxygen, since it determines the efficacy of oxygen intake, but usually estimated in terms of the diffusing capacity for carbon monoxide which is more straightforward to measure. Increased in exercise as greater lung expansion both enlarges the area and decreases the thickness of the gas exchange surface.

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.
References in periodicals archive ?
Single breath diffusion: Continuous measurement of mouth pressure throughout the test, The diffusion capacity DLCO: Intra Breath (IB).
The test, which measures diffusion capacity, is the most powerful predictor of survival for patients with Chronic Obstructive Pulmonary Disease (COPD), the third leading cause of death in the U.
Serial pulmonary function testing, including diffusion capacity, is routinely warranted-but all too often overlooked - in patients with skin-predominant dermatomyositis.
Additional findings showed that factors associated with long-term dyspnea in cancer survivors included presence of dyspnea before lung cancer surgery, reduced diffusion capacity (lung's ability to transfer oxygen into the blood) and lack of physical activity.
When done properly, the process of pneumotachography will produce accurate and precise flow and volume data for spirometry, diffusion capacity, lung volumes and exercise studies.
1], but a very low diffusion capacity, the following equation should be used:
Key words: Tobacco, lung function, exercise capacity, lung diffusion capacity.
Pulmonary diffusion capacity was measured by the steady state technique, using a Rahn and Otis end tidal sampler for obtaining alveolar air (2).
On pulmonary function tests, a mild-to-moderate restrictive pattern, reduced carbon monoxide diffusion capacity, and mild hypoxemia are exhibited.
A pulmonary function testing was done that showed restrictive physiology with moderately reduced diffusion capacity.
57 L (91%); diffusion capacity for carbon monoxide, 23.
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