Tests and Procedures
Nitric oxide test for asthma
Overview
An exhaled nitric oxide test can help with the diagnosis and treatment of asthma. Also known as the fractional exhaled nitric oxide (FeNO) test, this test measures the level of nitric oxide gas in an exhaled sample of your breath. This sample is collected by having you breathe slowly and steadily into a mouthpiece that's attached to a machine that performs the measurement.