The diffusing capacity of the lungs for carbon monoxide, often abbreviated as DLCO, measures how well oxygen and carbon monoxide can pass from the lungs into the bloodstream. This test evaluates the efficiency of the alveoli, the tiny air sacs in the lungs where gas exchange occurs. A higher DLCO indicates better lung function, while a lower value may suggest issues such as pulmonary fibrosis or emphysema. During the test, a patient inhales a small amount of carbon monoxide, and the amount that enters the bloodstream is measured. This helps healthcare providers assess lung health and diagnose potential respiratory conditions.