Peak expiratory flow (PEF) is the highest flow rate during forceful expiration, also known as the highest (large) expiratory flow rate, peak expiratory flow rate (velocity), etc. A reduced PEF in pulmonary function suggests that there may be a restriction of expiratory airflow that is influential.
PEF is one of the commonly used items for checking pulmonary ventilation function, which is related to the subject’s effort, lung capacity, respiratory muscle strength, and airway patency, and can reflect the ventilation function of the subject’s airway, provided that the effects of the first three are excluded.
PEF is generally judged by the percentage of the measured value of PEF to the normal expected value. If the PEF is ≥80% of the expected value, it suggests normal PEF or no expiratory airflow limitation; if the PEF is between 60% and 79% of the expected value, it suggests mild to moderate expiratory airflow limitation; if the PEF is <60% of the expected value, it suggests a more severe degree of expiratory airflow limitation.
If the PEF is lower than 60% of the expected value, it is suggested that the degree of expiratory airflow limitation is severe.