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 ?
1990) Carbon monoxide diffusing capacity, other indices of lung function, and respiratory symptoms in a general population sample.
Disproportionate decreases in diffusing capacity, which have also been suggested to be typical of RBILD, (3) may be useful as a guide to diagnosis, but only if the patient does not have significant emphysema or small airway remodeling because both of these lesions are well recognized causes of decreases in diffusing capacity.
Diffusing capacity is a pulmonary function measurement that attracts the most attention in altitude studies.
These results confirm data from human studies, where the inhalation of ultrafine carbon particles affected pulmonary diffusing capacity (Pietropaoli et al.
Respiratory complications of HCV infection include pulmonary vasculitis, alveolitis, decreased diffusing capacity, bronchiolitis obliterans organizing pneumonia, and mixed cryoglobulinemia associated with acute respiratory distress syndrome.
Safety measures included hypoglycemia (low blood sugar) rates, fasting blood glucose (FBG) and carbon monoxide lung diffusing capacity (DL(CO)), a measure of gas exchange capacity of the lung.
presents a significant risk in patients with preexisting pulmonary disease characterized by a decrease in pulmonary diffusing capacity and/or pulmonary blood flow.
9% increase in the diffusing capacity of the lung (DLCO).
Diffusing capacity was introduced as a clinical test in 1915 but never caught on because of the difficulty in measuring carbon monoxide.
Pulmonary function tests showed a reduced diffusing capacity of 67% predicted with oxygen desaturation on ambulation (Table 1), and a carbachol challenge (a test for airway hyperreactivity in asthma) was negative.
There were no clinically meaningful differences between the inhaled and injected insulin groups with respect to fasting blood glucose, carbon monoxide lung diffusing capacity (DLCO), and severe hypoglycemia.