Lung
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The contribution of the alveolar compartment to exhaled nitric oxide (alveolar nitric oxide or CA(NO)) can be calculated as a surrogate of distal inflammation. This value should be corrected for nitric oxide produced in the conducting airways which "back-diffuses" into the alveolar compartment (Corrected CA(NO)). Impulse oscillometry (IOS) (Nava et al., Am J Respir Crit Care Med 168:1432-1437, 2003) is used to derive values for peripheral airways resistance. ⋯ CA(NO) and IOS provide additional information to traditional measures of spirometry and tidal nitric oxide. Previous data reporting elevated alveolar nitric oxide in severe asthma may reflect back-diffusion of nitric oxide from the conducting airways into the alveolar compartment. Corrected CA(NO) and IOS may prove to be useful noninvasive measurements of small-airways disease.