PEAK EXPIRATORY FLOW RATE - The PEFR or peak expiratory flow rate is an effort-dependent assessment of a patients ability to forcibly expel air from their lungs. It is measured with a small hand-held device that has a mouthpiece attached to one end. Personal best values should be recorded so a baseline can be ascertained for the patient. PEFR measurement should be made routinely before and after inhalational treatments. Most moderate asthmatics and all severe asthmatics should monitor PEFR values at home and be familiar with the PEFR zones: PEFR 80-100% green zone (all clear); PEFR 50-80% yellow zone (suboptimal control or early exacerbation); PEFR less than 50% red zone (alert, indicating need for initiation of more aggressive treatment often involving corticosteroids)