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Peak Expiratory Flow Rate

From Mediwikis

Peak flow meter

The Peak Expiratory Flow (PEFR) is performed to assess the rate of air that a person can blow out of their lungs in one breath. It is an important indicator for respiratory disease such as Asthma or COPD, and while it is not as accurate as Spirometry, it can be quickly and easily performed in the outpatient or home setting, and is a common station in the OSCE. Accuracy of Peak Flow measurement is dependent upon operator skill, so it's important to prepare adequately to perform this, and be able to communicate the technique required to a patient.


Ask the patient about any difficulties breathing or any current respiratory problems that they're experiencing.

Explain to the patient the purpose of the PEFR, and what will be performed. Explain how PEFR can be used to measure the severity of respiratory illness and respiratory problems.

Nose holding/nose clips may be used, but offer no bias in results[1], and may reduce accuracy in children.[2]

Wash hands


  1. Connect a mouthpiece to the meter
  2. Set marker to zero
  3. Stand up straight, shoulders back.
  4. Hold the device in one or two hands, ensuring that fingers are away from the slider or it's path
  5. Breath out, then take as deep a breath as possible and hold it
  6. Form a tight seal around the mouthpiece with your lips.
  7. Breath out as hard and as fast as you can
  8. Write down the measurement

Repeat this 3 times (it might be helpful in younger patients to use teasing encouragement "You can do better than that!"

Explaining to a Patient

The vital steps required in giving any effective explanation for a patient are:

  • Check their understanding
  • Set the agenda (how to perform peak expiratory flow, why it is important)
  • Give information in small chunks, and check understanding after each
  • Check understanding of the technique by getting the patient to repeat the information back to you at the end
  • Offer the opportunity to ask any additional questions

For a thorough walk-through on communication skills and giving an explanation, see Giving an Explanation


  1. http://erj.ersjournals.com/content/21/5/876
  2. http://www.thoracic.org/statements/resources/pft/PFT2.pdf
  3. https://www.asthma.org.uk/advice/diagnosis/tests/