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. Author manuscript; available in PMC: 2009 Nov 30.
Published in final edited form as: Respir Physiol Neurobiol. 2008 Jul 31;163(1-3):166–177. doi: 10.1016/j.resp.2008.07.020

Figure 4. Illustrative data demonstrating the elimination rate vs. flow technique to estimate mean alveolar concentration and maximum airway flux.

Figure 4

The steady or plateau nitric oxide concentration can be measured at a series of constant exhalation flows, and then the elimination rate, (pl/s, product of concentration × flow) can be plotted as a function of exhalation flow, (ml/s). For flows > ~ 50–100 ml/s in adults, this relationship is approximately linear (solid circles), as predicted by the two-compartment model with axial diffusion. The slope minus a term proportional to the airway flux is an estimate of the mean alveolar concentration (C̅aNO, (pl/s) / (ml/s) = ppb), while the intercept is proportional to the mean maximum airway flux of NO (J̅' awNO, pl/s). Specific values for the coefficients “a” and “b” are described in Condorelli et. al. (2007), and depend on the flow range utilized.