Lung function tests information sheet

Contact the respiratory lab

The Children's Hospital at Westmead: 

Sydney Children's Hospital, Randwick:

Introduction

Respiratory or lung function tests assess how well your lungs work. They are important investigations which help diagnose suspected lung disease, help in planning treatments and to decide whether treatments should be continued, changed or discontinued.

About the tests

Spirometry

  • Spirometry measures the volume and pace of air you can forcefully exhale from your lungs after a maximal breath in.
  • This is measured with a device called a spirometer and has incentive computer games for children to help encourage them to blow out hard and fast.
  • This test may be performed before and after a bronchodilator, or puffer, (normally Salbutamol) to assess the effect of these medications on your lung function.

Fractional Exhaled Nitric Oxide (FeNO)

  • The FeNO test can help diagnose and manage Asthma.
  • It measures the amount of nitric oxide that is exhaled from a breath.
  • This test can be used to determine whether someone has increased airway inflammation and someone being treated for asthma is responding well to certain medications.

Lung Volumes (Plethysmography)

  • The Lung Volumes (Plethysmography) test allows us to determine a child’s Total Lung Capacity.

Diffusion Studies (DLCO) 

  • This test measures how well you can move, or ‘transfer’ gases from the lungs to the bloodstream.
  • In this test you will be asked to take a deep breath, in of a harmless gas mix, and hold your breath for around 10 seconds. 
     

Preparing for the test

Your child may be asked to withhold your inhalers or puffers for a specific time prior to the testing. These instructions will be given at the time of making the appointment.

IMPORTANT: If your child has been asked to withhold their medication however your child needs their breathing medication (ie. difficulty breathing, emergency situation) then they should take their medication and we can rebook the test for a later date. Your child’s safety comes first. Please also reschedule the test if your child is unwell, with any upper respiratory symptoms, at the time of testing as this can cause inaccurate test results. 

On the day of the test

Step 1

Your child will have their height and weight measured. 

Step 2

Your child will be asked to breathe through a mouthpiece that is connected to the lung function test equipment. All the tests are repeated several times to confirm the accuracy of the results. 

Step 3

Your child may be asked to perform a single test or a combination of tests. During testing, your child may be required to take big breaths in and out, blow out as hard and fast as possible or hold their breath for a few seconds. 

Step 4

A respiratory scientist conducting the test will explain everything required, in simple terms. While lung function testing is not usually uncomfortable, your child may exert themselves, become tired and/or feel a bit puffed out. 

Step 5

Dependent on the number and complexity of tests that have been requested, testing can take approximately 15 to 40-minutes.