Which describes the red zone in peak flow monitoring?

• A. PF 80-100%, no symptoms
• B. PF 50-80%, increased use of SABA
• C. PF <50% or no improvement after adding tx, very SOB, limited daily activities, symptoms >24h
• D. PF 60-70%, mild symptoms

Answer: (C)

Red zone signals dangerous airway obstruction and demands immediate action. It is defined as peak flow less than 50% of the patient’s best (or predicted) or not improving after adding treatment, and is usually tied to very shortness of breath, an inability to perform usual activities, and symptoms lasting more than 24 hours. The description here—the peak flow under 50% or not improving after additional therapy, with marked shortness of breath, limited daily activities, and symptoms persisting >24 hours—fits this high-risk category. In practice, you’d use the rescue inhaler now, reassess peak flow, and seek urgent care if there’s no improvement, following the person’s asthma action plan. By comparison, green zone (80–100% with no symptoms) indicates good control, and yellow zone (50–80% with increased SABA use or symptoms) signals caution and the need to adjust treatment to prevent progression.