Site-specific dosimetry was used to address the hypothesis that, given the airway dimensions of one subject, the airway dimensions of a second subject can be obtained by comparing responses to a modified bronchoconstrictor inhalation-protocol. Fourteen healthy, nonsmoking subjects received a high-resolution computed tomography (HRCT) scan prior to performing a methacholine challenge and measurement of change in forced expiratory-volume-in-one-second, (Delta FEV1). Scale factors of average length (L) and diameter (d) of the first six tracheobronchial airway generations were used to construct typical path lungs. The Multiple Path Particle Dosimetry (MPPD) model calculated surface density of methacholine. Airway circumference change, Delta C/C-0, was used to calculate Delta FEV1 in terms of airway smooth muscle sensitivity, K (cm/mu g/cm(2)). Virtual protocols were modeled such that fractional changes in Delta FEV1, "Delta Y", were independent of K. Eight subjects responded to methacholine with AFEV(1) > 3% and Ks from 0.011 to 35.8. For one virtual protocol, the linear relations between Delta Y and length and diameter scale factors had R(2)s respectively of 0.49 and 0.57. Within the limits of these measurements, the hypothesis is demonstrated; - any continuously increasing function of Delta Y vs. scale factor being sufficient to allow (without HRCT scans) classification of subjects according to airway size. (C) 2016 Elsevier Ltd. All rights reserved.