How to measure peak expiratory flow
What is peak expiratory flow?
Peak expiratory flow (PEF) measures how fast you breathe out when you try your hardest. It tells you how well your lungs are working. You measure PEF with a peak flow meter
, an inexpensive device that you can use at home.
- If you can breathe out quickly and with ease, you will have a higher number (higher peak flow rate). Your lungs are working well, and your asthma may not be bothering you.
- If you can only breathe out slowly and with difficulty, you will have a lower number (lower peak flow). This may mean that your lungs are not working well, even if you don't have any of your usual asthma symptoms.
You measure PEF as liters of air per minute.
How often should I measure PEF?
How often you measure your PEF depends on how severe your asthma is and how often you have asthma attacks. If you have severe asthma or cannot tell when you are having asthma symptoms, you may need to check your PEF twice a day, in the morning and in the evening. If you have mild asthma, you may not need to check your PEF daily and can instead monitor it by paying attention to symptoms. However, if any asthma symptoms develop, you may need to check your PEF. Talk with your health professional about how often you check your PEF.
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| Author: | Maria G. Essig, MS, ELS | Last Updated: March 22, 2007 |
| Medical Review: | Michael J. Sexton, MD - Pediatrics Harold S. Nelson, MD - Allergy and Immunology | |
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