The proportion of participants with > 12 % and 200-mL increases from their baseline FEV ( 1 ) with air - or heliox-driven bronchodilation was not different with respect to the proportion of participants with baseline FEV ( 1 ) 80 % ( 20 vs. 18 % , respectively ) and 80 % > FEV ( 1 ) > 50 % ( 36 vs. 43 % , respectively ) , but it was significantly greater with heliox-driven bronchodilation in participants with FEV ( 1 ) 50 % ( 43 vs. 73 % , respectively ; p = 0.01 ) .