A Cochrane review included 13 studies. Both FEV1 and FVC increased slightly after administration of a beta2-agonist. Two studies demonstrated a large increase in walking distance while one did not. Both morning and evening peak flow rates were higher than during placebo. A significant improvement in the breathlessness score was observed. Cough was reported to improve significantly.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals). Most of the studies had small sample size and some used very short-acting, outdated compounds.