In asthma self-management, which peak expiratory flow (PEF) percentage range defines the green zone (well-controlled) relative to personal best?

• A. 80-100% of personal best
• B. 50-79% of personal best
• C. 0-49% of personal best
• D. 60-80% of personal best

Answer: (A)

The green zone represents well-controlled asthma and is defined as a peak expiratory flow between 80% and 100% of your personal best. Personal best is the highest PEF value you’ve achieved during a period of good control, usually measured over time when symptoms are minimal. When your readings fall in this range, your airways are functioning close to your best, and your current treatment plan is appropriate. Readings in the yellow zone (about 50–79% of personal best) indicate caution and may prompt a review of meds or actions in your asthma action plan, while readings below 50% signal a potential medical emergency.