DLCO

D_LCO stands for the Diffusing capacity of the Lung for Carbon Monoxide, the test used to determine this parameter. D_LCO is the extent to which oxygen passes from the air sacs of the lungs into the blood. It was introduced in 1909.^[1]

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Mechanism of test

The D_LCO Test

This test involves measuring the partial pressure difference between inspired and expired carbon monoxide. It relies on the strong affinity and large absorption capacity of erythrocytes for carbon monoxide and thus demonstrates gas uptake by the capillaries that is less dependent on cardiac output^[2].

Factors reducing D_LCO

D_LCO can be reduced by the following:

1. Hindrance in the alveolar wall. e.g. fibrosis, alveolitis, vasculitis
2. Decrease of total lung area, e.g. emphysema.
3. Uneven spread of air in lungs, e.g. emphysema.
4. Cardiac insufficiency
5. Hemoglobin decrease in blood
6. Pulmonary hypertension

Factors increasing dlco include polycythaemia and increased pulmonary blood volume as occurs in exercise.

References

1. ^ Hughes J, Bates D (2003). "Historical review: the carbon monoxide diffusing capacity (DLCO) and its membrane (DM) and red cell (Theta.Vc) components". Respir Physiol Neurobiol 138 (2-3): 115-42. PMID 14609505.
2. ^ Sue DY, Oren A, Hansen JE & Wasserman K (1987). Diffusing capacity for carbon monoxide as a predictor of gas exchange during exercise. N. Engl. J. Med., 316(21):1301-1306.