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Peak expiratory flow rate monitoring in asthma

Lynn B Gerald, PhD, MSPH
Tara F Carr, MD, FAAAAI
Section Editors
Peter J Barnes, DM, DSc, FRCP, FRS
Robert A Wood, MD
Deputy Editor
Helen Hollingsworth, MD


The peak expiratory flow rate (PEFR, also known as a peak flow) is the maximal rate that a person can exhale during a short maximal expiratory effort after a full inspiration. In patients with asthma, the PEFR percent predicted correlates reasonably well with the percent predicted value for the forced expiratory volume in one second (FEV1). Monitoring the PEFR is useful for detecting changes or trends in a patient's asthma control, although significant testing variability makes it important to confirm or exclude airflow limitation with a more reliable test, such as spirometry.

The management of asthma depends in part on the ability of patients to monitor their condition on a regular basis. Self-monitoring can be performed by subjectively evaluating the frequency and severity of symptoms (figure 1). Patients can gain further information by monitoring peak expiratory flow rates (PEFRs), which provide an objective measurement of airflow obstruction, and can be performed accurately by most adults and children older than five years of age.

Peak expiratory flow rate monitoring in patients with asthma will be reviewed here. Other aspects of asthma management are presented separately. (See "An overview of asthma management" and "Overview of pulmonary function testing in children" and "Pulmonary function testing in asthma" and "Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)".)


Documentation of PEFR variability may be used to support the diagnosis of asthma. Patients can be asked to record PEFR upon awakening, in the evening, and before bed. Peak flow variability is calculated as the difference between the maximum and minimum peak flow in a day, expressed as a percentage of that day's minimum PEFR. Within-day or between-day variability in PEFR of >20 percent is characteristic of asthma [1]. (See "Pulmonary function testing in asthma", section on 'Peak expiratory flow'.)


The optimal role of long- or short-term daily monitoring in the ongoing management of asthma is unknown. The theoretic advantage is that daily PEFR monitoring can provide the patient and clinician with objective data upon which to base therapeutic decisions [2,3]. However, adherence to long-term monitoring is difficult to maintain [4]. According to some reports, adherence with home PEFR recording is satisfactory in the short term, but falls off considerably after several months. This suggests a significant limitation to this form of monitoring [5,6]. While patient adherence to PEFR monitoring is highly variable, connecting its use to the production of data relevant to concrete self-management activities may increase adherence [7].

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Literature review current through: Nov 2017. | This topic last updated: Dec 22, 2016.
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