Pathophysiology
Clinical meaning
Peak expiratory flow rate (PEFR) measures the fastest speed at which a patient can blow air out of their lungs, reflecting large airway function. In asthma, airway inflammation and bronchospasm narrow the airways, reducing the peak flow reading. Patients use a handheld peak flow meter daily to track their PEFR against their personal best value. Results are compared using a traffic light zone system: Green (80-100% of personal best = well-controlled), Yellow (50-79% = caution, use rescue inhaler), Red (<50% = medical emergency).