Impulse Oscillometry (IOS)

What is oscillometry?

Impulse Oscillometry (IOS) measures how much resistance the airways offer to airflow by sending gentle sound-wave pulses into the airway while the child simply breathes normally through a mouthpiece. Unlike spirometry, it doesn't require forceful breathing or precise technique — the child just breathes normally for a short period, which is why it works well for children too young to cooperate with spirometry instructions.

Why it's useful for younger children

Spirometry generally needs a child to be around 5–6 years old to perform reliably. Many preschool-age children with wheeze or suspected asthma are simply too young to manage the forceful exhale spirometry requires. Oscillometry fills that gap, giving an objective measure of airway resistance in children as young as roughly 2–3 years, depending on cooperation.

How the test is done

• The child sits comfortably and breathes normally through a mouthpiece with a nose clip on
• A device sends gentle, painless sound-wave pulses into the airway during breathing
• The test takes only a few normal breaths per attempt and is repeated for reliability
• No special breathing effort or coordination is required from the child

What it's used for

Oscillometry helps assess airway resistance in young children with recurrent wheeze, suspected asthma, or to track how a child's airways are responding to treatment — particularly useful as a child-friendly alternative or complement to spirometry in the pre-school age group.