DL_CO stand for The Diffusing capacity of the Lung for Carbon Monoxide, the test used to determine this parameter. DL_CO is the extent to which oxygen passes from the air sacs of the lungs into the blood. Carbon monoxide, with the chemical formula CO, is a colourless, odourless and tasteless gas. ... The alveoli (singular:alveolus), tiny hollow sacs which are continuous with the airways, are the sites of gas exchange with the blood. ... The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ...

The DL_CO 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^[1]. In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. ... Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ... Cardiac output is the volume of blood being pumped by the heart, in particular a ventricle in a minute. ...

DL_CO 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. Hb derease in blood
6. pulmonary hypertension

Detailed drawing of the alveoli from Grays Anatomy, 1918 - Schematic longitudinal section of a primary lobule of the lung (anatomical unit); r. ... Fibrosis is the formation or development of excess fibrous connective tissue in an organ or tissue as a reparative or reactive process, as opposed to formation of fibrous tissue as a normal constituent of an organ or tissue. ... In medicine, vasculitis (plural: vasculitides) is a group of diseases featuring inflammation of the wall of blood vessels. ... The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... Congestive heart failure (CHF), also called congestive cardiac failure (CCF) or just heart failure, is a condition that can result from any structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood throughout the body. ... HB is an abbreviation of: Hampton and Branchville Railroad (AAR reporting mark HB) hard black – a medium grade of pencil lead Helvetischer Bund, used as ICAO aircraft registration prefix (since 1935, before: CH) for Switzerland Hemoglobin is often abbreviated as Hb HB ice cream in Ireland, originally an abbreviation for... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... In medicine, pulmonary hypertension (PH) is an increase in blood pressure in the pulmonary artery or lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion. ...

References

1. ^ 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.