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).
Exam relevance
Risk factors: - Asthma diagnosis (primary indication for peak flow monitoring) - History of severe asthma exacerbations or ICU admissions - Poor perception of airway obstruction (poor symptom awareness) - Frequent use of rescue inhaler (> 2 days/week) - Exposure to known triggers (allergens, cold air, exercise)
Diagnostics: - Perform peak flow measurement daily, preferably in the morning before medications - Record personal best PEFR when asthma is well-controlled for 2 weeks - Calculate zone values: Green ≥ 80%, Yellow 50-79%, Red < 50% of personal best - Compare daily readings to personal best value - Track trends over time to detect gradual decline