diffusion capacity
Pulmonary function test measuring the lung's ability to transfer gas from alveoli to pulmonary capillaries, typically using carbon monoxide.
Full Definition
Diffusion capacity, formally known as diffusing capacity of the lung for carbon monoxide (DLCO), is a pulmonary function test that measures how efficiently gases transfer across the alveolar-capillary membrane. The test uses carbon monoxide as a tracer gas because of its high affinity for hemoglobin and minimal back-pressure from pulmonary capillaries. Patients inhale a test gas mixture containing a small amount of CO, hold their breath briefly, then exhale. The difference between inhaled and exhaled CO concentrations indicates the lung's diffusion capacity. Reduced DLCO values may suggest conditions affecting the alveolar-capillary interface, such as pulmonary fibrosis, emphysema, or pulmonary vascular disease. This test provides crucial information about lung parenchymal function beyond what spirometry alone can reveal.
Usage
Usage note: Commonly abbreviated as DLCO in clinical documentation.
In Context
- "The diffusion capacity test revealed a 40% reduction from predicted values, suggesting interstitial lung disease." — Pulmonary function report
- "Serial monitoring of diffusion capacity helps track disease progression in patients with idiopathic pulmonary fibrosis." — Clinical research protocol