| What is a Peak Flow
Meter?
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). Asthma sufferers blow into the device 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:
- Determine the severity of asthma
- Check your response to treatment during an acute
asthma episode
- Monitor progress in treatment of chronic asthma
and provide objective information for any possible
adjustments in therapy
- Detect worsening in lung function and thereby avoid
a possible serious flare-up in asthma with early intervention
- Assess asthma severity
One of the most important functions of the peak flow meter
is to help you and your physician evaluate asthma severity.
You will see a drop in peak flow readings even before
the symptoms of asthma (like coughing or wheezing) get
worse. Decreases in peak flow may indicate that you need
to increase your medication. The earlier a warning sign
is detected, the sooner the problem can be addressed.
Knowing your peak flow can be very helpful if you have
to call your physician after hours because of increasing
symptoms. The peak flow value can give the physician a
better idea of how you are doing and how you are responding
to treatment at home.
Another measure of asthma control is called peak flow
variability. A person without asthma or with well-controlled
asthma will consistently blow peak flows that vary less
than 15%. Most patients who have asthma know that asthma
symptoms are usually worse at night. A peak flow meter
is useful in monitoring the severity of asthma at night.
A decrease of 15% or greater from the previous night's
measurement may indicate nocturnal asthma. This is an
indication of how well your asthma is controlled.
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:
- Make sure the device reads zero or is at base level
- Stand up (unless you have a physical disability)
- Take as deep of breath as possible
- Place the meter in your mouth and close your lips
around the mouthpiece
- Blow out as hard and as fast as possible (one to
two seconds)
- Do not cough, spit or let your tongue block the
mouthpiece
- Write down the value obtained
- Repeat the process two additional times, and record
the highest of the three numbers in your chart
Your physician may ask you to record your peak flow before
and after using your rescue inhaler. If your medicine
is working you should see an improvement in your peak
flow reading. 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. The personal best peak flow is
the highest peak flow number a patient can achieve over
a 2-3 week period when his or her asthma is under good
control. To determine your personal best:
- Always use the same peak flow meter
- Record your peak flow twice a day for two weeks
- Ignore outlying values
Personal best values will change as children grow taller
and as disease status changes. Your physician will periodically
readjust your personal best.
Traffic light
system
Once you and your allergist/immunologist 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/immunologist,
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
improved with peak flow monitoring and reporting. Your
physician can use this data to design and adjust your
medication to achieve the best asthma control possible
for you. |
Related
Site
Overview
Peak Flow Meter