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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 3. Schematic of two-compartment model.

Figure 3

During exhalation, a steady state mean alveolar or peripheral concentration (C̅aNO ) enters the airway compartment (net transfer is convection minus diffusion) where upon additional NO is transferred from the airway walls. The alveolar or peripheral concentration represents the acinar region of the lungs (Weibel generations 17–23). The airway compartment represents the oropharynx and Weibel generations 1–16, and considers the increasing surface area per unit volume of the airway tree (i.e., trumpet shape). The contribution from the airways depends on the exhalation flow and is the sum of two terms: J̅' awNO =J̅awNO − D̅awNO *CNO. J̅' awNO is the mean maximum airway flux (picoliters/sec). D̅awNO is the mean airway diffusing capacity (or conductance). CNO is the airway compartment gas phase NO concentration which depends on axial volumetric position (V), and the airway compartment volume is Vaw. (T: trachea; BR: bronchus; BL: bronchiole; TB: terminal bronchiole; RB: respiratory bronchiole; AD alveolar duct; AS: alveolar sac)