In order to characterize the mechanical effects of thoracic percussion per se in lung parenchyma, we analyzed respiratory impedance parameters by impulse oscillometry (12 healthy subjects) and lung mechanics by the least square method (6 healthy subjects) before (PRE-TP) and after (POS-TP) thoracic percussion, and after a deep-breath-maneuver (POS-DB). Pulmonary resistance was similar among PRE-TP, POS-TP and POS-DB while pulmonary dynamic compliance showed a significant reduction after TP (mean +/- SEM: from 0.15 +/- 0.018 L/cmH(2)O to 0.12 +/- 0.016 L/cmH(2)O; P = 0.001), returning to basal values (mean +/- SEM: 0.15 +/- 0.021; P = 0.004) after DB. Reactance parameters (AX and f (0)) evaluated by oscillometry increased significantly after TP, returning to previous values after DB. Total impedance (Z5) and respiratory system resistance at 5 Hz (R5) did not differ significantly among experimental conditions. Our data strongly suggest that thoracic percussion can promote changes in respiratory mechanics compatible with lung collapse and/or pneumoconstriction, which are, however, reversible by deep inspirations.