Measurement of exhaled nitric oxide. A new lung function test?

Nitric oxide (NO) is a gas molecule produced endogenously in the lungs. It can be detected in the exhaled air of animals and humans. Nitric oxide can be generated in the air passages by a synthase which is induced in several cell types by exposure to proinflammatory cytokines. Its induction is blocked by glucocorticoids. An increased concentration of nitric oxide can be found in the exhaled air of patients with asthma and other inflammatory lung disorders. Gas analysers for measuring nitric oxide in exhaled air have recently been made commercially available. The test is non-invasive, simple to perform, and can also be used in patients with reduced lung function. The method seems to provide a unique non-invasive means of diagnosing and monitoring inflammation of the air passages, and in the future the test may become a useful tool in a clinical setting. Preliminary recommendations for measurements and technical standardization have recently been proposed by the European Respiratory Society.