The primary function of the lungs is to allow the exchange of gases (oxygen and carbon dioxide) with the blood. While the inhaled oxygen-rich air is diffused into the blood, carbon dioxide from the blood is received by the lungs and exhaled. This function of the lungs may be affected by various conditions such as asthma and bronchitis, where the air passages become narrowed causing difficulty in breathing. Many tests are performed to evaluate lung function. One such test, diffusing capacity of the lungs for carbon monoxide or DLCO, measures the diffusion capacity, the lungs’ ability to exchange gases with the bloodstream.
Several hours before the test, you are instructed to stop smoking, eating and taking any inhaled medications such as bronchodilators. To perform the test, you will inhale air that contains a small amount of a tracer gas (carbon monoxide). Inhalation is performed orally through a well-fitted mouthpiece, while your nostrils are clipped shut. The breath is then held for 10 seconds after which you are instructed to exhale rapidly. The exhaled air is tested to determine carbon monoxide levels, which indicates the amount of gas exchange. This is a quick test and is a safe procedure.
Diffusion capacity can measure whether lung function is worsening or improving with treatment. It may help diagnose various lung conditions such as pulmonary embolism, emphysema, pulmonary hypertension and lung hemorrhage.