What should you know about spirometry in childhood asthma?

It is usually considered when a child can follow instructions and make a reliable effort. The test is one part of an assessment; symptoms, examination findings and the child's pattern of breathing also matter.

A child breathes into a spirometer through a clean mouthpiece. After a full breath in, they blow out as hard and as long as instructed. The device records airflow and the amount of air exhaled. The clinician may repeat the manoeuvre to check that the readings are consistent.

Sometimes the test is repeated after prescribed reliever medicine. A change between readings can show that narrowed airways respond to treatment, which may support an asthma diagnosis. A normal result does not by itself rule out asthma, particularly if symptoms come and go or the child is well on the day.

The clinician will explain the result in the context of age, height, symptoms and medicines. Spirometry is different from simply checking oxygen levels and does not require a blood test.

Tell the clinic about current inhalers, recent breathing symptoms and any illness on the day. Follow the appointment team's instructions about whether to use or pause a particular inhaler; do not stop a prescribed medicine without checking first.

Comfortable clothing can make deep breaths easier. Explain that the child will be asked to make strong, repeated blows, and reassure them that the staff can pause if they feel distressed, dizzy or unwell. Bring the child's inhalers and spacer if requested, along with any symptom record.

The reading is most useful when the child follows the instructions closely. If the first attempt is difficult, the team may offer coaching or arrange another assessment rather than treating one imperfect blow as the whole answer.

Contact the child's healthcare team if coughing, wheezing or breathlessness is becoming more frequent, waking them at night, limiting play, or requiring reliever medicine more often than advised. They may need an earlier review rather than waiting for a planned lung function test.

Seek emergency help if the child is struggling to breathe, cannot speak or drink normally because of breathlessness, becomes unusually drowsy, or develops blue or grey lips. Follow the child's written asthma action plan if one is available, and use prescribed reliever medicine as directed while arranging urgent help.

You could ask: What will my child need to do during the test? Should any inhaler be used differently beforehand? What did the result show when compared with the child's symptoms? Would repeating the test or using another assessment help? What signs should prompt us to seek urgent care?