Peak Flow Meter

What is a peak flow meter? It is a device prescribed by your doctor to help you monitor your child's asthma. It is a plastic tube about 8 inches long with a mouthpiece attached. Your child takes a deep breath, and then blows out as hard and fast as he can. This makes a small plastic knob move up the tube. The harder the breath, the farther it moves up. The knob measures how much air your child is able to force out of the lungs in one breath.

What does this mean?

• The more open the airways, the more air can be forced out of the lung, the higher the peak flow reading.
• If the airways are constricted, such as during an asthma attack, less air can be forced out of the lung. This registers as a lower peak flow reading.

How does a peak flow meter help monitor your child's asthma?

• Take several measurements of your child's peak flow when he is well. Record this reading as your child's "personal best." Really encourage him to see what his actual highest peak flow is. Write this down so you know what his peak flow ideal is.
• Normal peak flow readings are based on a child's height as follows:
• Normal ranges are plus or minus 75. For example, normal peak flow for a 60- inch tall child would typically be 300 to 450.
  • 40 inches – 125
  • 45 inches – 175
  • 50 inches – 250
  • 55 inches – 325
  • 60 inches – 375
  • 65 inches – 450
  • 70 inches – 525
  • 75 inches – 575

This list is a general guideline. Learn what your own child's peak flow typically is when he is well. It may be greater or less than this chart.

The peak flow can help in two ways:

1. Help you assess how bad an asthma attack is. If your child normally can get a peak flow of 450, but during an attack can only get 250, you know he needs an albuterol treatment. Checking another peak flow 30 minutes after a treatment can help you assess improvement.

2. Help you assess whether or not your child has mild, underlying quite wheezing on a daily basis. Sometimes it is not always obvious that your child is struggling. Checking peak flows periodically can help catch this. If your child usually has peak flows or 500 when well, and lately he has only been able to get 350 or 400, he may need some extra treatment, even if you don't notice any worsening symptoms.