Lung Disease & Respiratory Health Center

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. For more information, see the topic Lung Function Tests.
• Checking your 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. For more information on 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 machine.
• 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 medicine.
• 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.