Forced Oscillation/Impulse Oscillimetry (IOS)

Forced Oscillation testThis 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.


Performing the test

  1. The patient places the mouthpiece in past the teeth, with the tongue under it and keeps a tight seal on the mouthpiece
  2. The patient breathes normally for 15 to 30 seconds as the sound waves pulse through the airways
  3. The patient comes off of the mouthpiece. Three reproducible efforts are needed

IOS measures resistance, respiratory impedance, reflectance and distribution disorders. This test may be done with or without bronchodilator or with a bronchial challenge.