The accuracy of peak flow
monitoring depends on your effort during the test. Results will be inaccurate
if you do not follow directions or do not give your best effort during testing.
The following factors also may affect the results of peak flow
Using medicine that expands the airways in the
lungs within 4 hours before the test may improve test results.
sedatives before the test may worsen test
People who have pain while breathing may not be able to breathe
normally. So the results of their tests may be misleading.
What To Think About
Your doctor may do a complete series of lung
function tests to confirm a lung disease, monitor the progression of lung
disease, or monitor the effectiveness of treatment. To learn more, see
Lung Function Tests.
peak expiratory flow (PEF) provides information that
may help you decrease your asthma symptoms and keep your lungs as healthy as
possible. The benefits of better lung function may include improved quality of
life, fewer emergency department visits, greater personal control and
confidence, and reduced use of oral steroid medicines, antibiotics, and
bronchodilators. To learn more about controlling your asthma, see the topic
Asthma in Teens and Adults.
When using a
home peak flow meter, it is best to use the same meter over time. Different
brands of meters give different results. If you change your peak flow meter,
you need to redetermine your personal best measurement using the new
Wash your meter according to the manufacturer's directions
to prevent growth of bacteria and fungi.
PEF is lowest in the early
morning and highest in the afternoon. If you measure your PEF only once a day,
do so first thing in the morning before using any bronchodilator
People with intermittent or mild persistent asthma may
not need to check their PEF every day. But if symptoms develop,
checking peak expiratory flow often for a period of time may be helpful in
bringing asthma under control.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
Holcroft CA, et al. (2003). Measurement
characteristics of peak expiratory flow. Chest, 124(2):
National Institutes of Health (2007). National Asthma Education and Prevention Program Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma (NIH
Publication No. 08–5846). Available online: