A  peak flow meter for asthma is like a thermometer for a fever. It’s a tool that helps you monitor what’s going on inside your body. In some cases when you are not feeling well, you may feel “hot” or “feverish,” but when you take your temperature with a thermometer, it is normal. With asthma, sometimes you may feel your breathing is fine, but when you measure it with a peak flow meter, your lung function is slightly decreased. A peak flow meter can help you determine airway changes and thus, better manage your asthma.

  • Using a peak flow meter

A peak flow meter is a simple, portable, inexpensive device that measures air flow, or peak expiratory flow rate (PEFR) . Some look a little like a kazoo. Asthma sufferers blow into them quickly and forcefully, and the resulting peak flow reading indicates how open the airways are, or how difficult it is to breathe. If used appropriately, a peak flow meter can be a valuable tool in your asthma management. It can be used as a tool to :

  1. determine the severity of asthma;
  2. check your response to treatment during an acute asthma episode;
  3. monitor progress in treatment of chronic asthma and provide objective information for any possible adjustments in therapy;
  4. detect worsening in lung function and thereby avoid a possible serious flare-up in asthma with early intervention;
  5. and diagnose exercise-induced asthma.

One of the most important functions of the peak flow meter is to help you and your allergist evaluate asthma severity. Peak flow readings fall before the symptoms of asthma are otherwise noticed. Decreases in peak flow may indicate that an adjustment in therapy is needed, such as adding a medication or making other changes in your treatment plan. The earlier a warning sign is detected, the sooner the problem can be addressed. Many patients with asthma have established a plan with their allergist so they know which medication to add if their peak flow drops below a certain level.

Peak flow meters are available over-the-counter, but should be used with the recommendation of your allergist, who can demonstrate the proper technique for use. Your allergist or other health care staff can instruct you on how and when to record the peak flow readings on a chart and what to do if the peak flow readings fall below a certain level. Patients should bring their peak flow meters to the physician’s office to check the accuracy of the unit as well as to recheck their proper use.

  • Measuring asthma

Asthma is usually worse at night, although some patients sleep through the night unaware of lower peak flow levels. When we sleep, there is a decrease in the amount of oxygen in the blood. In people with asthma, this fall in oxygen may happen more often and last longer. A peak flow meter is useful in monitoring the severity of asthma at night. You do not have to wake up at night to use the meter; simply compare your morning reading with your reading the night before to determine the degree of nocturnal (night) asthma. A decrease of 15% or greater from the previous night’s measurement may indicate nocturnal asthma, which you can work with your allergist to treat.

The use of regular peak flow monitoring has been shown to help patients gain a clearer idea of how their lungs are functioning. Without objective measurements, it is difficult to determine which “triggers” cause lung function to worsen. To pinpoint asthma triggers, you can write down peak flow meter readings before and after exposure to allergens such as dust mites, irritants such as cigarette smoke, exercise or other events that may trigger asthma. Peak flow readings during different seasons of the year can help to identify problems that may be caused by pollens or cold, dry air. The benefits of properly used peak flow meters make them worth considering for any asthma patient, especially if the asthma has been difficult to manage.

  • How to use a peak flow meter

There are several steps to properly using a peak flow meter. You should blow hard on the meter to get the best reading possible, and repeat this attempt three times. Record the best of the three trials. All three measurements should be about the same to show that a good effort was made each time. This is especially important when parents are evaluating their child’s asthma.

Follow these general steps when using a peak flow meter :

  1. Make sure the device reads zero or is at base level.
  2. Stand up (unless you have a physical disability).
  3. Take as deep of breath as possible.
  4. Place the meter in your mouth and close your lips around the mouthpiece.
  5. Blow out as hard and as fast as possible (one to two seconds).
  6. Do not cough or let your tongue block the mouthpiece.
  7. Write down the value obtained.
  8. Repeat the process two additional times, and record the highest of the three numbers in your chart.

It is also helpful to record readings before and after using inhaled bronchodilators. Two different symbols, such as “X” and “O,” may be used to graph these readings each morning and night. Your allergist can gain a great deal of information by reviewing these readings. This also will help you to gain a better awareness of your lung function.

Keep a chart of peak flow readings, with each day recorded in a column, to show how your asthma symptoms are doing. Graphs for plotting peak flow readings often come with the devices and can be photocopied for regular use.

Peak flow meters need some care, so make sure to follow the cleaning instructions enclosed with each unit. This will help to ensure its accuracy.

  • Establishing your personal best reading

Although your predicted “normal” peak flow is determined by height, age and gender, it is preferable to gauge asthma control by comparing daily peak flow recordings with your “personal best” reading. This is defined as the highest measurement you can achieve in the middle of a good day, after using your inhaled bronchodilator.

Your allergist can help you determine your personal best by using treatment to normalize your lung function, and then accurately measuring lung function using a highly sensitive in-office measurement machine called a spirometer. Lung function values can then be compared to your own peak flow device to set your personal asthma management goals. For children, peak flow goals should not decrease over time, but should be readjusted upward on a yearly basis to account for growth.

  • Traffic light system

Once you and your allergist have established your personal best peak flow, you should make every effort to maintain values within 80% of this number so you feel your best. The following traffic light system can serve as an easy guide:

Green zone—Peak expiratory flow rate (PEFR) 80-100% of personal best. All systems “go.” You are relatively symptom-free and can maintain your current asthma management program. If you are on continuous medication and your peak flow is constantly in the green zone with minimal variation, your physician may consider gradually decreasing your daily medication.

Yellow zone—PEFR 50-80% of personal best. “Caution,” as asthma is worsening. A temporary increase in asthma medication is indicated. If you are on chronic medications, maintenance therapy will probably need to be increased. Contact your physician to fine-tune your therapy.

Red zone—PEFR below 50% of personal best. “Danger,” your asthma management and treatment program is failing to control your symptoms. Use your inhaled bronchodilator. If peak flow readings do not return to at least the yellow zone, contact your allergist, who will help you employ aggressive therapy. Maintenance therapy will have to be increased.

These traffic light zones are broad guidelines designed to simplify asthma management. Successful control of asthma depends upon a partnership between the patient and the physician. This open communication and exchange of information can be enhanced with peak flow monitoring and reporting. Your physician can use this data to design and adjust your therapy for optimal asthma management.