Peak Flow Meter use in Adult Asthmatics

What is a Peak Flow Meter (PFM)?

A peak flow meter is a small hand-held instrument used to measure how fast air can travel through the large airways of your lungs. The peak flow meter records the "peak" or highest airflow as air leaves your lungs. It "measures" how open or how narrow your airways are. When you experience asthma symptoms, your large airways become narrow or "obstructed". Air passes through more slowly and your peak flow "falls".

Why should I use a Peak Flow Meter?

By using a peak flow meter, you can become more involved with your asthma management. You will be able to provide your doctor with valuable objective information about your asthma. This information, along with symptoms you are feeling and physical examination, helps you and your doctor design a treatment plan for you. Changes in your peak flow can help you to:

  1. Detect early changes in your airways before you are even aware that your asthma may be getting worse. You can modify your medication schedule as advised by your physician before your condition worsens.
  2. Identify conditions in your environment that may be "triggering" your symptoms.
  3. Determine whether your medications are working as they should. Medications can be adjusted (increased, changed or decreased) per your physician's advice, as needed.

When should I use my Peak Flow Meter?

Your physician will prescribe a schedule that he/she feels is best for you. General recommendations are as follows:

  1. Take readings twice a day, at the same time, to establish a baseline or "personal best" value for you. Your doctor may have you take readings in both before and after you have taken your inhaled medication (bronchodilator).
  2. Take a reading when you notice a change in your symptoms.
  3. Take a reading when you have been exposed to known "triggers" of your asthma.
  4. Monitor your peak flow when you change your medication schedule.
  5. Monitor your peak flow when you develop any symptoms of an upper respiratory infection.
  6. Monitor your peak flows when you are traveling or vacationing. Changes in your environment can affect your asthma.

How do I use a Peak Flow Meter?

  1. Set the indicator on the meter to the bottom of the scale before each breath.
  2. Take all measurements in a standing position, if possible. If you can not stand take all readings in the same position.
  3. Remind yourself to breathe out only through your mouth, not through your nose (use nose clips if necessary).
  4. Hold your peak flow meter in a way so your fingers do not obstruct the hole in the back (this will cause falsely high readings), or the arrow that rises when you breathe out.
  5. Take a slow, deep breath in and close your lips tightly around the mouthpiece.
  6. Blow out as hard and as quickly as possible. Remember that you want maximum speed of expiration, not prolonged expiration. The "peak flow" occurs at the early part part of your breath.
  7. Repeat once or twice and record the best measurement on your peak flow record.
  8. Remember that different brands of peak flow meters measure your peak flows differently, so be consistent with the brand you use.

Are there problems with using Peak Flow Meters?

  1. Improper usage will give you incorrect readings. Remember that this is an effort dependent instrument.
  2. Overusage can make your shortness of breath worse.
  3. Focusing on and relying upon peak flow readings too much, can lead you to ignore other valuable information from body sensations or emotional signals, thereby preventing adequate response to critical changes in your asthma.
  4. Peak flow meters fail. If you feel much better than your peak flows indicate, have your physician or nurse check you with another meter.

What are peak flow zones?

Your predicated peak flow is usually considered to be the higher value of either your "personal best" (the highest reading you can reach when your asthma is in good control) or that obtained from a table (based on average values obtained from patients of the same height, age and gender). Your peak flow can generally be described as falling into one of three zones:


Zones  Percentage of Predicated Peak Flow  Symptoms 
Green 80-100% healthy, usually no symptoms
Yellow 50-80% asthma worse, may have symptoms; need to identify and remove triggers; medicines may need adjustment
Red <50% in danger of developing complications; need immediate guidance from your physician