In 2003,approximately two thirds of persons with current asthma used one or more inhaled medications during the preceding 3 months, and the proportion using inhaled medications increased with levels of symptom severity. Approximately half of all respondents with asthma used a B2A-S rescue inhaler, or one third used an inhaled corticosteroid,and one fifth used a B2A-L inhaler. Each symptom severity level had a similar sample of inhaled medication use.
Source: cdc.gov