Lung function tests (infants)

This page explains lung function tests for infants and what to expect when your child comes to Great Ormond Street Hospital (GOSH) for the procedure.

Breathing tests can be performed in babies to assess how well their lungs are working. These tests can help to monitor the growth and development of the lungs and the effectiveness of treatment (eg antibiotics).

The person bringing your child for the test should have ‘Parental Responsibility’ for them. Parental Responsibility refers to the individual who has legal rights, responsibilities, duties, power and authority to make decisions for a child. If the person bringing your child does not have Parental Responsibility, we may have to cancel the test.

Who does the infant tests?

Tests for babies and young children are only carried out by fully trained respiratory physiologists, and supervised by specialist nurses.

What do the tests involve?

Breathing tests are safe and painless, and will only be carried out when your baby is well and free from a cold, cough or wheeze. The tests are carried out while the baby sleeps. To perform the test babies will need to be in a deep sleep, to help achieve this a spoonful of sedative syrup, called chloral, is used to help them fall into a deeper and often slightly longer sleep allowing time for the test to be carried out.

Learn more about infant lung function tests with chloral hydrate.

A small mask, connected to a meter (or sensor), is gently placed over the nose and mouth to monitor the baby’s breathing pattern which is displayed on a computer screen. The tests assess how well the lungs are working. For example, we assess:

  • how quickly the baby can remove waste gases (such as carbon dioxide) from his/her lungs
  • how much air is held at the end of each breath which allows us to calculate the size of the lungs
  • how fast the baby can “blow out” in order to find out if there is any narrowing of the air passages (or airways).

Throughout the tests, the baby’s oxygen saturation (the amount of oxygen in the blood) and heart rate will be monitored. Parents are welcome to stay with their baby at all times and ask questions. We also measure the baby’s weight and length.

How long do the tests take?

We can only record the baby’s breathing pattern during periods when he/she is sleeping quietly. It will take approximately 2 hours to complete the measurements for all the different assessments. Total testing time including the time spent asking a few questions (for example, family history of asthma) and waiting for the baby to fall asleep is usually completed within 3-4 hours.

When will we get the results?

The results for your test will be uploaded onto our electronic patient record system for your doctor to view, these will be discussed with you at your next clinic appointment

Compiled by:
Lung Function unit Great Ormond Street Hospital
Last review date:
November 2022
Last review :Nov 202