History, technical and regulatory aspects of exhaled nitric oxide.

The history of nitric oxide (NO) in exhaled breath as a marker of inflammation is summarized, followed by measurement aspects of exhaled NO including NO excretion models of NO in the airway, the estimation of flow-independent NO exchange parameters and issues with the standardization of these methods. Regulatory considerations in the US are also presented. A brief summary of the state of the art for clinical application of exhaled NO is also included.