How to Take a Home Lung Function Test

Assess Your Asthma at Home

Peak Flow Meter
Children can learn to use their own peak flow meter at a young age.. Joshua Davidson, MD

What Is A Home Lung Function Test?

A home lung function test allows you to measure your peak expiratory flow, or PEF, to monitor your asthma control and breathing status. Patients who have asthma, or other lung diseases, use peak flow meters to objectively monitor their condition, allowing them to stay on top of any impending respiratory issues. 

Learning how to perform and incorporating PEF into your asthma action plan is an important skill for every asthmatic.

The process is simple to learn and takes only a few steps, and you can 


To prepare for performing a home lung function test you simply need to own a peak flow meter and a chart that shows your expected results. This is available and should be part of your asthma action plan. Your doctor or asthma educator should provide instructions about how often to perform PEF and be able to elaborate on any questions or concerns you may have about the task. 

How to Perform PEF

Before doing a home lung function test to measure your PEF, be sure to remove any excess saliva, food, or gum you may have in your mouth. In general, clear all potential breathing obstructions from your mouth, to ensure maximum test efficiency. Also, be sure to check the peak flow meter for any obstructions or foreign objects. After you have done this, simply follow these 8 simple steps to effectively perform the test.

  1.  Set your peak flow meter to point 0.
  2. Attach the mouthpiece to the peak flow meter.
  3. Stand up to guarantee that you are getting a deep breath. Always stay in the same position throughout the test so that results are not affected. 
  4. First take a deep breath in and then place the peak flow meter mouthpiece closely and tightly around your lips. Always avoid putting your tongue inside the mouthpiece.
  1. Breathe out as forcefully as you can, using a huff like motion. Do not breathe out in excess of one second.
  2. Take down the reading on the gauge.
  3. Place the peak flow meter back to point 0 before blowing again.
  4. Repeat the blowing and recording process two more times. Always go again if you cough, or experience any other complications. 

After blowing into the peak flow meter a total of three times, record your highest value for the day. If instructed, also record the other readings.

Will I Feel Strange?

Some patients will be intimidated by the proposition of breathing in and out very quickly multiple times in a row. Thankfully, although you may feel light headed the first few times around, or cough, no serious health risks are involved in performing the home lung function test.

If you begin to feel strange, simply take a deep breath and allow your body and mind to calm down. If you have symptoms you should talk with your doctor as it may indicate poor control of your asthma.
If for some reason you continue to feel strange, comfortable, or anxious after a test, contact your doctor or another medical professional.


What You Can Expect from the Results

Home lung function tests using a peak flow meter monitor the day to day status of your asthma. This measurement shows you how much air you are able to forcefully breath out when trying your absolute hardest. With this in mind, you can expect to view your peak expiratory flow after completing the test and see if you need to take action based on your asthma action plan

You will then compare your PEF levels to what is expected. Using charts provided by a medical professional that compare your performance against normal values based on sex, race, age, and height, you will either continue your current treatment or need to take action to make sure you are not getting worse. 

Most plans are based on the zone system with green, yellow, and red areas, just like a stoplight. In the green or go zone, you are doing well and just need to maintain the status quo. You have minimal symptoms or impairment. In the yellow or caution zone, you need to pay more attention and like take some steps to prevent worsening of acute asthma symptoms.  The red zone means you were unable to manage your escalating symptoms. 

Your plan will provide steps to take, but you need to seek medical attention. The goal is to step up your treatment and head off problems before you need to head to your doctor’s office or the emergency room. The red, yellow, and green colors of the stoplight are known by everyone and are associated with a safety mentality. Categorizing asthma in this way makes it easy for parents and patients to understand what they need to be doing and the seriousness of what is going on.

By doing the test regularly you will determine your personal best measurement and what is normal for you. Your best efforts will eventually be used to determine treatment rather than a strict comparison to the norms based on your height and weight.

Whenever your PEF levels fall below the expected levels set out in your asthma action plan, you should follow the instructions and contact a medical professional immediately indicated. Tackling asthma in a timely manner is key to treating the condition successfully. 

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National Heart, Lung, and Blood Institute. Expert Panel Report 3 (EPR3): Guidelines for the Diagnosis and Management of Asthma Accessed on April 16, 2016.

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