Those who take medication for wheezing due to chronic bronchitis should measure the PEFR before and after treatment, and know their PEFR zones:

• PEFR <50% of personal best is the Red Zone. This indicates a severe attack and the need for more aggressive treatment, often requiring corticosteroids.
• PEFR 50-80% of personal best is the Yellow Zone. It indicates suboptimal control or an early attack.
• PEFR 80-100% of personal best is the Green Zone. It indicates good control.