Table 3 Representative studies of the effect of a combination of long acting bronchodilators and inhaled steroids in COPD.

Study	No of patients	Duration(years)	Mean FEV1(% predicted)	Comparison	Outcome
TRISTAN31	719	1	44%	Salmererol 50 μg/fluticasone 500 μg twice daily	25% reduction in rate of exacerbations. 39% reduction in rate of exacerbations requiring steroids
Hanania90	363	0.5	42%	Salmererol 50 μg/fluticasone 500 μg twice daily	No difference in number of exacerbations and time to first exacerbation
Calverley27	510	1	36%	Formoterol 24 μg/budesonide 400 μg twice daily	Prolonged time to first moderate exacerbation; risk reduction 42%. Reduced exacerbation rate by 24%
Szafranski26	413	1	36%	Formoterol 24 μg/budesonide 400 μg twice daily	Reduced exacerbation rate from 1.87 to 1.42 per patient year