Fig. 4
Distribution of specific ventilation estimated from the N2 washout of a four compartments physical model. Results from each of twelve repetitions are represented (A to I, in light gray, with \(F_{{N_{2} }}^{I}\) step from 0.5 to 0, and J to L, in dark gray, with \(F_{{N_{2} }}^{I}\) step from 0.1 to 0), with different symbols for each test. The reference distributions are shown in black. EELV is the end-expiratory lung volume; vent is the sum of the fractional compartmental ventilations (∑γ); and vd is the dead space volume estimated by: Fowler’s technique (for the generalized model, panels a and b) or the complement of total ventilation (for the classical model, panels c and d)