Lung Function Test For Children – What Can You Expect by Dr Srikanta J T

8 min read

Written by Dr. Srikanta J T

Dr. Srikanta J T

Lung Function Test For Children

Children have an immature immune system and can fall sick frequently. Viral infections in the form of cough and cold are quite common, especially school-going children. Cold, cough and flu often result in the accumulation of fluids inside the lungs. These conditions may resolve on their own or with the help of medications. But in the case of persistent respiratory issues which don’t seem to resolve even with medical intervention, doctors may prescribe lung function test for children to understand the underlying causes.

If your child has been coughing or experiencing breathing difficulties, it is most certainly an issue with the lungs. Your doctor would advise you to consult a pulmonologist – a doctor specializing in treating lungs and related diseases. Now, they cannot treat your child without a proper test. They often depend on a lung function test to understand what is happening. What exactly happens in a lung function test? What can you expect and what should you prepare for? This article explains.

In This Article

Lung Function Test in Children – What is it?

A lung function test, more commonly known as the pulmonary function test, is a series of tests to check your child’s lungs. These tests will determine how healthy and effective your child’s lungs are.

A pulmonary function test is a non-invasive test that will measure the lung’s efficiency. If your child already has lung-related issues and is on medications to help them breathe, the lung function test will help to understand how effective the medicines are.

The test can be effective only if your child cooperates. This is not like a blood test where you can hold the child down by force and get the test done. A pulmonary function test requires your child to understand the instructions given and cooperate fully. Unless they do their part, the test cannot happen.

What is Carried Out During a Lung Function Test?

Lung function test Spirometry

As mentioned above, the aim of the pulmonary function test is to measure the amount of air breathed in and out. It will precisely calculate how much air your child’s lungs are pulling in and how the airflow is – in and out of the body.

A lung function test can be done in two main ways. There will be more tests or variations to the tests under these methods of testing.

1. Spirometry

Chances are you have seen this device. A spirometer will have a mouthpiece, which your child will have to breathe into. On the other end, this device is connected to a computer, which will measure the quantity and speed of the air your child’s lungs are breathing in and out.

For a child who may get intimidated with a tube hooked up to them and a computer, doctors may mask it as a game. They might ask them to blow a horn or some other breathing toy. When presented as a series of games, the child will cooperate well and perform their best. They will be well occupied and won’t feel scared to do the test away from their parents.

However, kids will be kids and it is most natural for them to not cooperate beyond a certain point. Sometimes it may require you to make multiple visits to the clinic to complete the test.

2. Peak Flow

Peak flow is a part of the spirometry test. Here the medical practitioner will ask your child to blow out as hard as they can. It is to measure how strong the lungs are and how much air it can push out. Though it is very similar to tests the doctor might have taken in his office, spirometry will have more accurate results.

Expect your child to become very tired, frustrated, or uncooperative in some time. This test can be difficult to complete for a small child. Hence, you may need to make multiple trips before the test is complete.

3. Bronchodilator Response Test

If your child has a lung issue, they mostly will be on some medication to help them breathe better.

A bronchodilator is a medicine that help open up the breathing tubes in the lungs. If your child is on this medication for breathing issues, the medical care professional will want to check the effect of this medicine. They will ask your child to inhale the bronchodilator and check their lung function after a gap of 15 minutes.

First, your child undergo the test without inhaling the medicine. Then they will be given the medicine. After 15 minutes the test will be repeated to check the effect of the medicine. The difference between the readings before and after inhaling the medicine will show how effective the medicine is, for your child.

4. Plethysmography

Here your child will sit inside or stand inside an air-tight box-like structure for the purpose of testing.

5. Forced Oscillometry

Some young children may not be able to breathe in and out on cue as instructed. They won’t be able to breathe out or blow with enough force to record readings for the test. In such cases, forced Oscillometry is done to record accurate readings.

Don’t worry, though the name says “forced” your child will not undergo any pain or discomfort. In this test, the doctor will clip your child’s nose and seal their lips tightly around the mouthpiece. Now, a technician or a nurse will hold your child’s cheeks firmly. The machine will then send small bursts or puffs of air into your child’s mouth through the mouthpiece.

When your child is breathing regularly, these puffs of air pushed inside will help measure the flow of air in their lungs. It can measure the resistance and compliance of the lungs, thus helping understand the efficiency of the lungs.

What Does a Lung Function Test Reveal?

A lung function test for children helps measure the efficiency or performance of the lungs. The tests can reveal the following.

  • Tidal Volume – The amount of air inhaled/exhaled during the test.
  • Minute Volume – Number of inhales/exhales per minute.
  • Vital Capacity – The maximum amount of air your child can exhale after inhaling to the maximum limit.
  • Functional Residual Capacity – The air left behind in the lungs after regular exhalation.
  • Residual Volume – The air left behind in the lungs after exhaling to the maximum limit.
  • Total Lung Capacity – The full capacity of the lungs when completely full with air.
  • Forced Vital Capacity – How much can be forcefully exhaled after a quick full inhalation.
  • Forced Expiratory Volume – The amount of air that expired in the first, second, and third seconds of the Forced Vital Capacity test.
  • Peak Expiratory Flow Rate – The fastest rate at which air can be forced out of the lungs.
  • Forced Expiratory Flow – The average flow rate in the middle of the FVC test.

Can You Medicate Your Child Before The Test?

Can You Medicate Your Child Before The Test

So, can you give your child their regular lung medications before going for the test? No, not unless the doctor has cleared it.

Sometimes, children might have severe breathing issues and will be highly dependent on medications. In such cases, the doctor will advise you about when to administer the medicine and the dosage for the same. In cases, where the medicine is not an absolute necessity, the doctor will want to test your child’s lungs’ original capacity, without the extra help from the medicine.

These medicines might interfere in showing the exact level of lung function. With false readings or readings influenced by medicines, the doctors won’t be able to gauge the lungs’ efficacy.

How do You Prepare a Child For a Lung Function Test?

How do You Prepare a Child For a Lung Function Test

Any test can be quite scary for a child, especially if it is a very young child. The minute you tell them you are taking them to the doctor, they panic, and their body tenses up. This can have a big effect on their breathing too.

Here are a few ways in which you can prepare your child for the tests to come.

  1. You need to remain calm and patient with your child. They will most likely refuse or cry and scream their lungs out in resistance but not breathe as requested. Stay calm and it can have a positive impact on your child and make them cooperate.
  2. A child will most likely be scared the minute the doctor utters the word test or takes the child away from you. . Explain to your child exactly what will happen and why it is done. Reassure them that it won’t be painful and that there are no needles involved.
  3. Ensure you schedule a test as per your child’s comfort. For small children who have daytime naps, ensure you fix the appointment after their nap time. The same applies to their hunger/mealtimes.
  4. The child has to be comfortable and composed. Ensure their environment is not intimidating. If needed, carry a toy or their favorite things to help them stay calm and relaxed.
  5. When the staff explains the entire procedure, let your child listen in. If your child does not understand or if you are unable to follow, the staff will repeat it again.
  6. A cold can interfere with the test readings. If your child has caught a cold or has mucus formation, let your doctor or testing lab know about it immediately. They can either reschedule the test or decide if they should go ahead with the tests as per plan.

How Long Does a Lung Function Test For Children Take?

These tests won’t take long. They might take just about 30 minutes. However, there are many factors that can influence the time taken. The tests can take more time, in the following situations:

  • Your child refuses to cooperate and needs reassurance to take the test.
  • The child does not understand instructions and requires repeated tests or instructions.
  • Your child is on lung medications and a bronchodilator test is required.
  • The child starts crying midway and requires to take a break and come back for another round.

[Read : Asthma in Toddlers: Symptoms and Treatment]

Side Effects of a Lung Function Test in Children

Side Effects of a Lung Function Test in Children

The lung function test is a non-invasive test and is completely safe. However, your child might experience a few side effects such as:

  • Feeling dizzy or light-headed during the test. This can happen due to controlled and forceful breathing during the tests.
  • Shortness of breath.
  • Coughing, a very normal phenomenon in both kids and adults taking a pulmonary function test.
  • Asthma attacks are due to deep inhalations if your child already has asthma.

Avoid taking a pulmonary function test for their child if the child has

  • Some eye surgery in recent times. Breathing pressure might damage the eyes.
  • Undergone a recent surgery in the abdomen or chest area.
  • Heart conditions.
  • Aneurysm.
  • Respiratory infection or TB.

You should remember that these tests measure the functioning of your child’s lungs. Sometimes, the readings may not be very accurate.

The accuracy of the tests greatly depends upon

  • Your child’s cooperation during the test in breathing in and out as required.
  • Any medication your child is on for improving lung function.
  • Pain medications if any.
  • Bloating of the stomach may affect the extent to which your child can take deep breaths.
  • Your child’s physical state on the day of the test. If they are too tired or exhausted, they may not be able to perform their best on the test.

A lung function test does precisely as the name suggests – it tests the functioning of your child’s lungs. Though quite challenging, this test can help doctors determine the health of your child’s lungs and diagnose correctly. This test can help in understanding the lungs better and address the various issues within.

[Read : Tuberculosis in Children]


1. At What Age Can Children Undergo Lung Function Tests?

In most cases, a child above the age of 6 can undergo the spirometry test. At this age, they will be able to understand and follow instructions during a test. Some children can perform the test even earlier. It all depends on the child and how well they can communicate with others.

Infant Pulmonary Function Testing is also possible for infants with lung or breathing issues. They will undergo sedation for easy completion of the test.

Read Also: Breathing Problems In Children – Causes And Symptoms

Dr. Srikanta J T, MBBS, Diploma in Child Health (DCH), Diplomate of National Board(DNB), Fellowship in Pediatric Pulmonology and Sleep Medicine(NUH, Singapore), Training in Interventional Pulmonology
Consultant - Paediatric Interventional Pulmonology, Allergy and Sleep Medicine, ASTER CMI Hospital
10 years of experience

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