At what age do bronchodilator drugs work?

Using a modification of the forced oscillation technique we have measured respiratory resistance before and after nebulised salbutamol therapy in 32 wheezing children aged 7 months to 3 years 7 monts. 12 of the children were also studied in a total body plethysmograph. No child under 18 months of aged showed a greater than 5% fall in resistance or any fall in thoracic gas volume. In contrast, 18 of 20 children over 20 months of age showed a fall in resistance greater than 20%. [ABSTRACT FROM AUTHOR]