Impulse oscillometry is a noninvasive procedure that can be performed within few minutes. The purpose of the procedure is to measure the resistance of the small and large airways, as well as the reactants of the airways. ... In contrast to spirometry, the test performs measurement during tidal breathing. Impulse oscillometry measures the resistance (R) of the airways and lungs to differing frequencies, and is calculated from pressure and flow signals where pressure is in phase with flow (when the pressure wave enters the lungs unopposed by any recoil force).