Study	Reason for exclusion
Golabi 2006	Four weeks of treatment, only tiotropium alone and salmeterol/fluticasone treatment groups, cross‐over design
Hara 2007	Eight weeks of treatment, only tiotropium alone and salmeterol/fluticasone treatment groups, cross‐over design
Mittmann 2010	No tiotropium plus LABA treatment group
Singh 2008	Two weeks of treatment, no tiotropium plus LABA treatment group, and of cross‐over design