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 ?
The south savo social and health services association (essote) will ask for your offer of clinical physiology for future diffusion capacity / spirometer equipment.
5%), FEV1/FVC%: 65, and the diffusion capacity of lung for carbon monoxide was 49.
The ADC depicts the specific diffusion capacity, microscopic structure and organization of a biological tissue.
The EasyOne Pro performs single breath Diffusion Capacity (DLCO) testing, spirometry and full lung volumes in just 20 minutes.
Pulmonary functions testing showed severe restriction and severe reduction in diffusion capacity (FVC: 2.
Other less common symptoms include scrotal pain and swelling, headaches, seizures, ataxia, central and peripheral neuropathies, impaired lung diffusion capacity, keratitis, and uveitis.
The measurement of Functional vital capacity (FVC) and Carbon monoxide diffusion capacity (DLCO) is useful in determination of the interstitial lung disease, which could lead to the PAH development.
However, there is consistent evidence that smokers who have emphysema and fibrosis can be extremely dyspneic and may present with normal flow rates on spirometry, normal total lung capacity, and strikingly low diffusion capacity.
Pulmonary function studies showed a combined obstructive and restrictive defect with no change post bronchodilator and reduced diffusion capacity.
This edition includes clinical connections that link chapter concepts and real-world applications in the clinical setting; new and redrawn full-color illustrations; revised chapters to reflect the most recent best practices, including more on the mechanisms of pulmonary ventilation, the components of blood, and the control of ventilation; revised and new discussions of the anatomy of the respiratory system; new sections on predicted normal values, the rapid shallow breathing index, and how carbon dioxide is transported from the tissues to the lungs; and updated content on lung volumes and capacities, the diffusion of pulmonary gases, the medullary respiratory centers, sleep stages, and oxygen diffusion capacity at high altitudes.
Serial pulmonary function testing, including diffusion capacity, is routinely warranted-but all too often overlooked - in patients with skin-predominant dermatomyositis.
Cardiac evaluation proved uneventful, but pulmonary function tests revealed a diffusion capacity of 17.

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