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What is a peak flow meter?
A peak flow meter (PFM) is a plastic handheld device used for home monitoring as part of a comprehensive asthma management plan.
Who should use one?
Anyone can get a PFM without a prescription. Asthma specialists usually recommend them for patients with moderate or severe asthma, with mild but daily symptoms, or with nighttime asthma. They are also very helpful for someone who is newly diagnosed, or for those who have difficulty sensing the onset of symptoms. Children as young as 5 or 6 years old are able to use a PFM.
When should I use it?
PFMs are usually used in the morning, upon awakening, and in the evening. This allows the person to see the nighttime effect of asthma, even if that person is asymptomatic. Even those who don't have asthma experience a drop in lung function during the night. But for someone who does have it, the drop may be more significant. Also, for the person who doesn't have asthma, the reading should be back up to normal at the evening reading. For someone with asthma, a drop between morning and evening indicates that lung function has deteriorated throughout the day.
Other times to use a PFM:
- Before and after exercising, to check for exercise-induced asthma
- Before and after taking medication, to see if the desired effect is being realized
- If you experience daily symptoms
- If symptoms come on suddenly, without warning
- To check the effect of certain triggers
- When experiencing symptoms, the PFM gives an objective measurement of respiratory function
Discuss with your physician the need to use a PFM.
How do I use a PFM?
- Once you have your own PFM, bring it to an office visit to have your physician or nurse check proper technique and recording.
- Establish a baseline reading. This will be used as your "personal best," against which daily readings will be gauged. The baseline should be done when you are not having any symptoms (if possible). Age and gender will affect your baseline reading. As a child grows, his or her baseline will need to be adjusted.
- Keep a consistent time for using your PFM.
- Remove any food or gum from your mouth.
- Stand up straight (or sit, if necessary).
- Make sure your fingers are not obstructing the movement of the marker.
- Take a deep breath.
- Close your mouth over the mouthpiece, so your lips form a close seal.
- Keep your tongue away from the mouthpiece.
- Blow out as hard and as fast as you can. The marker is moved by the initial burst of air from the lungs, so continuing to blow is ineffective.
- Write down the value.
- Repeat two more times, being sure to reset the marker.
- Record the best (highest), not the average, of the three readings. Three values in the same range indicate you are using the PFM correctly. Clean the PFM according to manufacturer's directions.
- Store away from dirt and dust.
What will I learn by using a PFM?
By keeping a daily log of your PFM readings, you are monitoring your lung function on a daily basis. A low reading (80 percent to 85 percent of your personal best) can indicate that you are becoming sick, or are about to have asthma symptoms. It indicates an obstruction in the flow of air from your lungs (due to increased inflammation or constriction), alerting you to a decrease in respiratory status. This gives you and your doctor an objective measurement with which to make any necessary changes in your treatment, before experiencing an asthma attack.
The readings alert you to early changes that allow you time to take action, such as by changing/increasing your medication schedule (according to your written management plan) before your symptoms worsen. Studies have shown that patients who use a PFM on a regular basis experience fewer and less severe asthma attacks, fewer trips to the emergency room, and fewer hospitalizations. Readings at 80 percent to 100 percent of your personal best tell you that you are in good control of your asthma. Using a PFM gives you time to be in better control.
Green, yellow or red?
A "green, yellow, red" system is often used with a PFM. A reading in the "green" zone indicates you are doing well. Your lungs are functioning at 80 percent to 100 percent of your personal best. You should not need to make any changes in your treatment plan. With continued readings in the green zone, your doctor may discuss a trial of lowering some of your medication doses.
A reading in the "yellow" zone indicates you are functioning at 50 percent to 80 percent of your personal best. It means there is narrowing of your bronchial tubes, and minimal exposure to triggers may elicit symptoms. Consult your written management plan to see what step to take next (eg, make a change in your medication schedule) to regain control over your asthma. With a reading in this zone, you are probably experiencing an increase in your asthma symptoms. Your doctor may want to be notified if your peak flow values drop below a certain point.
A reading in the "red" zone is a sign that your lungs are functioning at less than 50% of your personal best. It is important to take whatever action you and your doctor have previously discussed, according to your treatment plan (eg, begin the use of more potent medications, call your physician, be seen at an emergency room).
A goal of using a PFM on a regular basis, is to detect changes in your respiratory status before you begin experiencing symptoms. When you visit your physician, make sure you bring your peak flow chart, so the two of you can review it together.
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