DLCO, or diffusing capacity of the lungs for carbon monoxide, is a test that measures how well oxygen and carbon dioxide are exchanged in the lungs. It specifically assesses the ability of the alveoli, the tiny air sacs in the lungs, to transfer gases into the bloodstream. A higher DLCO value indicates better lung function, while a lower value may suggest issues such as pulmonary fibrosis or emphysema. During the DLCO test, a patient breathes in a small amount of carbon monoxide mixed with air. The amount of carbon monoxide that is absorbed into the blood is then measured. This helps doctors evaluate lung health and diagnose various respiratory conditions.