What level of improvement in FEV1 would be expected after bronchodilator if the asthma is classified as moderate?

• A. 10-19%
• B. 20-39%
• C. 40-59%
• D. 60-79%

Answer: (C)

Reversibility of airway obstruction after a bronchodilator is a key way to gauge how much of the obstruction in asthma can be reversed with medication. In moderate asthma, you expect a substantial bronchodilator response, meaning FEV1 increases by about 40% to 60% from baseline. So the best choice is the range that corresponds to roughly a 40-59% improvement. To think about it, compute percent improvement as (FEV1 after bronchodilator − baseline FEV1) ÷ baseline FEV1 × 100. For example, a baseline FEV1 of 1.5 L improving to about 2.1 L is roughly a 40% increase. Smaller improvements (around 10–20%) would suggest milder reversibility, while very large improvements (60% or more) are less typical for moderate asthma and may indicate very good reversibility or milder disease.