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 "Use of pulmonary function testing in the diagnosis of asthma" and "Patient information: Asthma treatment in adolescents and adults (Beyond the Basics)".)
ROLE OF PEFR MONITORING
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 . However, adherence to long-term monitoring is difficult to maintain . According to some reports, adherence with home PEF recording is satisfactory in the short term, but falls off considerably after several months. This suggests a significant limitation to this form of monitoring [3,4]. 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 .
Studies evaluating the efficacy of PEFR monitoring for improving various outcome measures in asthma have yielded conflicting results [6-19]. A number of studies failed to demonstrate an advantage of using PEFR monitoring over symptom monitoring to guide self-management actions [6-8,11,13-15]. Studies that demonstrated an improvement in outcomes, such as decreased health care utilization and improved quality of life, included a comprehensive management approach, which did not separate out the specific effect of PEFR monitoring [9,12,19]. Further research on the efficacy of regular peak flow monitoring by patients is needed.