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Date of last update: 10/19/2017.

Forum Name: Asthma

Question: What explains changes in peak flow readings?

 kellysmum2002 - Tue Jan 01, 2008 10:57 am

I have asthma, and I take my peak flow reading three times per day-morning, mid-day, and before I go to bed. Most days my readings are around 400. Twice in the mid afternoon I have had a 450-I have no explanation for this phenomenon. My question is, why is it that some days I can only manage in the 350's to 370's, no matter that I'm using my medication and not exerting myself? Could it be attributed to anxiety, or is it that my asthma is simply worse some days?

Thank you.
 Dr. Chan Lowe - Sat Jan 12, 2008 10:16 pm

User avatar Hi Kellysmum2002,

Peak flows are used to estimate lung function related to asthma as you are describing. When asthma symptoms increase, peak flow amounts go down.

What you are likely seeing when your peak flow drops is an increase in lung bronchospasm causing your lung function to decrease some. Some fluctuation in the peak flow is a normal. If your peak flow drops more consistently it may be a warning of an impending asthma flare. If they drop for one or two readings then go back to normal it may simply be some intermittent spasming that is not predictive of impending flares unless the decreased episodes are occurring frequently.

Best wishes.

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