diffusing capacity

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diffusing capacity

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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

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.
Farlex Partner Medical Dictionary © Farlex 2012

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.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

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.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
References in periodicals archive ?
Improvement of alveolar-capillary membrane diffusing capacity with exercise training in chronic heart failure.
(1972) Cigarette smoking and pulmonary diffusing capacity. (Transfer factor).
"After the man stopped keeping birds, his lung volume increased and diffusing capacity apparently improved slightly" (16 words).
(%) Clinical (e) <.001 Serologic <.001 Morphologic Radiographic (f) <.001 Pathologic (g) <.001 NSIP <.001 OP <.001 NSIP/OP overlap .07 Interstitial lymphoid aggregates .02 with GCs Diffuse lymphoplasmacytic infiltrates .006 Multicompartment involvement (h) .14 Intrinsic airway disease .12 Pleural or pericardial effusion or .05 thickening Pulmonary vasculopathy .29 UIP pattern <.001 Abbreviations: BMI, body mass index;DLCO, diffusing capacity of the lungs for carbon monoxide;FVC, forced vital capacity;GC, germinal center; IPAF, interstitial pneumonia with autoimmune features;NSIP, nonspecific interstitial pneumonia;OP, organizing pneumonia;TLC, total lung capacity; UIP, usual interstitial pneumonia.
In addition, modified Rodnan skin score (mRSS) for the degree and the extension of cutaneous sclerosis; pulmonary function tests for the assessment of forced vital capacity (FVC) and diffusing capacity or transfer factor of the lung for carbon monoxide per unit alveolar volume (DLCO/AV); chest high-resolution computed tomography (HRCT) scan for the detection of lung fibrosis; 2D echocardiography (2D-ECHO) for the screening of pulmonary artery hypertension (PAH); and laboratory tests for the determination of serum creatinine level, autoantibodies, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were also performed.
The major types of pulmonary function tests include measurement of lung volume using spirometry and quantization of diffusing capacity. Measurements of maximal respiratory pressures and flow volume loops, which record forced inspiratory and expiratory flow rates are also useful in specific clinical circumstances.
Pulmonary function tests (PFT) including dynamic lung volume, diffusing capacity of lung for carbon monoxide (DLCO) and DLCO divided by alveolar volume were performed.
Routine special investigations should include an HRCT scan (to estimate heterogeneity, integrity of fissures and degree of tissue destruction, and to exclude occult malignancy), full pulmonary function testing (including measurements of forced expiratory volume in 1 second, forced vital capacity, residual volume (RV), RV/total lung capacity (TLC), TLC, carbon monoxide diffusing capacity and 6MWD), arterial blood gas measurement and echocardiography (to exclude pulmonary artery pressures >50 mmHg).
A variety of other tests are often helpful in narrowing the differential diagnosis--for example, chest imaging, blood eosinophil measurement, allergy testing, bronchial challenges, diffusing capacity of the lung for carbon monoxide, lung volumes, and elasticity.