What is the role of peak expiratory flow (PEF) measurement in the evaluation of asthma symptoms?

Updated: Nov 20, 2020
  • Author: Michael J Morris, MD, FACP, FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Peak expiratory flow (PEF) measurement is common in the ED because it is inexpensive and portable. Serial measurements document response to therapy and, along with other parameters, are helpful in determining whether to admit the patient to the hospital or discharge from the ED. A limitation of PEF is that it is dependent on effort by the patient. FEV1 is also effort dependent but less so than PEF. FEV1 is not often used in the ED except in research settings.

PEF in the ED can be compared with asymptomatic (baseline) PEF, if known. Unfortunately, patients often do not know their asymptomatic PEF. Moreover, the reference group for the ideal PEF percent predicted (based on age, sex, height) may not be accurate for the patient population seen in many inner-city EDs, since most equations are based on white populations.

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