Role of Peak Expiratory Flow Meter in Asthma Self-Management

Abstract

IntroductionPEFR is the maximum flow rate generated during a forceful expiration after a full inspiration, and it is expressed in litres/minute. PEFR primarily reflects large airway flow. It is dependent on the lung recoil, airway calibre, effort, and muscular strength of the patient. Maximal airflow occurs during the effort-dependent portion of the expiratory manoeuvre; thus, a low PEFR at many times could be due to poor effort rather than airway obstruction. FEV₁, a dynamic measure of flow used in formal spirometry, is a better indicator of airway obstruction than PEFR. PEFR usually correlates well with FEV₁; this correlation decreases in patients with asthma as airflow diminishes. Even though PEFR and FEV₁ have a good correlation, this may be lost once the airflow decreases. Unlike FEV₁, which is a volume-based parameter, PEFR is a flow-based measurement and does not reflect peripheral airway involvement. Hence, it is more suitable as a monitoring tool than a diagnostic one. Nonetheless, it is a simple, easy-to-perform PFT that is particularly valuable in the diagnosis and monitoring of obstructive airway disease, especially asthma.