Multiple breath nitrogen washout (MBNW) information sheet
Contact details
Introduction
Multiple breath nitrogen washout (MBNW) is a sensitive, non-invasive measurement used to assess how well the lungs are working. This test involves looking at the distribution of air in the lungs and measures how efficiently gases are mixed.
About the test
MBNW testing involves breathing 100% oxygen and then measuring the expired nitrogen at the mouth. With each subsequent breath, nitrogen is washed out until the concentration in the lungs is 2%. MBNW provides the measurements of the lung clearance index (LCI) and the functional residual capacity (FRC).
This information may assist diagnosis of an illness, determine the nature and severity of a disease process and/or determine the response to therapy.
Risks
If your child is unwell and requires medication such as bronchodilators before testing, their safety is considered the first priority. The MBNW test can be rescheduled, please contact us (details below) if your child is unable to attend.
In some cases patients who have been unable to withhold medications may still have MBNW testing performed.
As MBNW is a sensitive measure of lung function, the technical performance of the test is vital to ensure accuracy of results. If your child is unable to follow the procedure for the test, it may be attempted on a future date (at the discretion of the referring doctor).
Please note: In some cases, your referring doctor may ask your child to stop taking medications prior to the test. Please make sure you follow these instructions.
Preparing for the test
Please allow 1 hour for clinical testing.
On the day of the test
At least one respiratory scientist will be present throughout the entire MBNW test. On arrival your child will have their height and weight measured. The respiratory scientist will explain the test procedure to you and your child.
Step 1
Your child will either use a mask with some putty (used to create a seal to prevent air leakage) or a mouthpiece with a nose clip to perform the test. The choice of a mask or mouthpiece will be determined by the respiratory scientist based on the age and/or experience of your child.
Step 2
Your child will either sit upright by themselves on a chair or on their parent/guardian鈥檚 lap to watch a movie encouraging relaxed breathing.
Step 3
Once your child is breathing in a relaxed manner, the test will begin.
Step 4
The test will end when 5 breaths have occurred below the nitrogen target of 2%.
Step 5
The test will be repeated twice to ensure reliability and accuracy of the results.
Additional trials may be performed if they are deemed technically unacceptable by the respiratory scientist (signs of air leak, variable breathing, variable results). After the completion of the MBNW test, your child may perform an additional test called Spirometry if they are at least 5 years of age.