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 ?
Conclusions: Caution is warranted in the use of lung-volume-reduction surgery in patients with emphysema who have a low FEV and either homogeneous emphysema or a very low carbon monoxide diffusing capacity.
Standardization of the Single-Breath Diffusing Capacity in a Multicenter Clinical Trial", CHEST October 2007; 132/4:1191-1197.
1) showed no significant correlations between functional status and lung involvement parameters such as pulmonary arterial hypertension, dyspnea, Carbon Monoxide Diffusing Capacity and FVC, and concluded that the HAQ-DI is of no value as an outcome measurement in SSc patients.
Many of their patients had a restrictive pattern of pulmonary function, and all had a decreased diffusing capacity.
Because of that, you can get relatively normalized lung volumes and spirometry, but what characterizes these patients is a severe reduction in diffusing capacity.
Diffusing capacity is a pulmonary function measurement that attracts the most attention in altitude studies.
Patients were eligible for the studies if they had a diagnosis of pulmonary fibrosis confirmed by CT scan or by biopsy and if they had a forced vital capacity (FVC) that was 50% of predicted value or greater and a diffusing capacity of the lung for carbon monoxide that was 35% of predicted value or greater.
These results confirm data from human studies, where the inhalation of ultrafine carbon particles affected pulmonary diffusing capacity (Pietropaoli et al.
Those with unexplained restrictive lung function, impaired diffusing capacity, or HRCT findings consistent with ILD were referred for transbronchial or wedge biopsy.