Dr.Kamini Silvarajan MD/AAAM

Editorial Board: Dr.Kamini Silvarajan MD/AAAM

Peak Expiratory Flow Rate

Peak Expiratory Flow Rate: Definition – PEFR measures how fast a person can breathe out or exhale air. It is a test that measures how efficient the lungs are working.

This test is done by a peak expiratory flow monitor – a small handheld device with a mouthpiece at one end and a scale with a moveable indicator – usually a small plastic arrow to show the reading (see diagram below).
Peak Expiratory Flow Rate (PEFR) or Peak Flow Monitor

How to perform PEFR test: 

  1. Breathe in as deeply as possible.
  2. Blow into the PEFR mouthpiece as hard and fast as possible.
  3. Do this 3 times, and record the highest flow rate.

How to Prepare for the PEFR test:

Loosen any tight clothing that might restrict your breathing. Sit up straight or stand while performing the tests(results are BEST when standing).

How the PEFR test will make you feel:

There is generally no discomfort. Rarely, but repeated tests may cause some light headedness.

Why the PEFR test is performed:

The PEFR test is generally used to diagnose and monitor lung diseases such as: 

  1. Asthma
  2. COPD or Chronic Obstructive Pulmonary Disease
  3. After a lung transplant
Self or home monitoring can assist to determine whether treatments are working or detect when your condition is getting worse.

PEFR normal results:

The PEFR normal reading changes based on a person’s age, sex, and size. PEFR measurements are most useful when a person compares the number on a given day with the previous result for comparison to determine action plan.

A drop in PEFR reading can signal the onset of a lung disease flare, normally when it happens with symptoms such as: 

  1. Increased cough
  2. Shortness of breath
  3. Wheezing
Early treatment may be needed to prevent complications.

What does abnormal results mean.

PEFR – Peak air flow during exhalation decreases when the airways are blocked or obstructed.

Asthmatic patients can use peak expiratory flow monitoring to monitor their lung function at home. This can be very helpful, especially in asthma patients whose peak flow reading sometimes gets low before they develop breathing symptoms. If the fall in peak flow is treated early, symptoms can be avoided and an asthma attack too can be avoided.

If you note that your peak flow is decreasing, tell your health professionals.

PEFR risks:

There are no significant risks.

Peak expiratory flow rate measurements are not as accurate as the spirometry measurements – Any small changes in your peak flow reading may not mean significant changes in your lung function,therefore the above description of a PEFR or Peak Flow has proven to correct an early correction for an asthma attack by self precautionary measures before help is needed,called or comes.