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Using your peak flow meter

What is a peak flow meter?

A peak flow meter is a portable, handheld device that is used to measure how well air moves out of your lungs. Measuring and taking regular peak flow readings is an important part of managing your asthma. A peak flow meter measures how fast air comes out your lungs when you exhale forcefully. This measurement is called a ‘peak expiratory flow’, or PEF.

Why use a peak flow meter?

Readings from a peak flow meter can help you or your child recognize early symptoms of worsening asthma. A person’s PEF might drop hours or even days before any asthma symptoms occur. Peak flow readings will help you to detect changes that might be signs of worsening asthma. This allows you to adjust your asthma medication to prevent an asthma attack.

How do I use my peak flow meter?

A peak flow meter is simple to use, even for children over 4 years old. To use you peak flow meter:

  • Stand up straight holding the meter horizontally.
  • Push the indicator to the bottom of the meter.
  • Inhale deeply.
  • Place your mouth over the mouthpiece making sure your lips seal over the mouthpiece so that no air escapes.
  • Blow out forcefully in a single blow.
  • The indicator will slide up the scale. The number that it stops on is your peak flow reading.
  • Keep a record of that number.
  • Repeat this test 2 more times, remembering to slide the indicator back to its start position near the mouthpiece.
  • Record the highest of the three readings in My Peak Flow software or your asthma diary.

When should I check my peak flow?

Take your peak flow readings at the same time each day, say once in the morning and again at night. Taking a reading each day will help you to detect drops in airflow early. If your morning PEF is below 80% of your personal best reading then follow your asthma action plan and check your PEF more frequently. Seek advice from your doctor.

How do I determine my “Personal Best”?

Your ‘personal best’ PEF is the highest peak flow number you or your child can achieve. Your personal best PEF is important because it is the number to which all of your other peak flow readings will be compared.

Your doctor will develop an asthma action plan based on your personal best PEF. To determine your personal best peak flow number, take peak flow readings twice a day for 2-3 weeks when asthma is in good control with no asthma symptoms. Take the readings at the same times, in the morning and in the evening before medication.

What are asthma zones?

Your asthma peak flow zones are part of an asthma action plan determined by your doctor. The zones determine when to take asthma medication to prevent an asthma attack and when to seek emergency assistance. All of this information would be recorded in your asthma action plan. Peak flow readings are often classified into 3 zones of measurement according to the American Lung Association; green, yellow, and red.

The color system is based on the colors of street traffic lights.

The Green Zone means 80 to 100 percent of the usual or normal peak flow readings are clear. A peak flow reading in the green zone indicates that the asthma is under good control.

The Yellow Zone means 50 to 80 percent of the usual or normal peak flow readings indicate caution. It may mean respiratory airways are narrowing and additional medication may be required.

The Red Zone means less than 50 percent of the usual or normal peak flow readings indicate a medical emergency. Severe airway narrowing may be occurring and immediate action needs to be taken. This would usually involve contacting a doctor or hospital.

Keeping your peak flow records

It is important to keep accurate records of your peak flow readings and asthma symptoms to communicate with your doctor on asthma action plans and treatment. My Peak Flow software will remind you to take a reading and will chart and track your peak flow readings and asthma.


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About Kellie

Kellie is 37 years old and together with her brother Steve makes up the My Health Software team.

She helps on the websites and gathering news for the programs. Kellie worked in the medical industry prior to having her two children (8 and 6) and has a strong interest in self awareness and management of health conditions.