Forced Oscillation/Impulse Oscillimetry (IOS) Make an Appointment Ask a Question Refer Patient Reviewed by Amy Olson and George Zeman (April 01, 2014) This test is often used with patients too young or patients unable to perform other pulmonary testing. It is a technique used to measure resistance of the airways using application of sine waves to the airway. It requires minimum cooperation from the patient. IOS measures resistance, respiratory impedance, reflectance and distribution disorders. This test may be done with or without bronchodilator or with a bronchial challenge. This information has been approved by George Zeman BS, RRT, CPFT and Amy L. Olson, MD, MSPH (April 2014).