Fig. 2.

Three models of the airway used for calculating 3 airway resistances [average, total, and airway (R_avg, R_T, and R_A)]. A: model of a cylindrical airway with a constant radius of r_avg and total length of L used for computing R_avg. B: model of an airway with both longitudinal variability in the cross-sectional area and noncircularity of the cross-sectional shape used for computing R_T. The cross section was assumed elliptical with a major and minor radius of a_i and b_i and the segmental length of l_i. C: model of an airway with circular cross sections with the radius r_i and the longitudinal variability in the cross-sectional area used for computing R_A.