Changes from baseline FVC , FEV ( 1 ) , FEV ( 1 ) / FVC , FEF ( 25-75 ) % , FEF ( max ) , FEF ( 25 ) % , FEF ( 50 ) % , and FEF ( 75 ) % were significantly larger with heliox-driven versus air-driven bronchodilation in participants with baseline FEV ( 1 ) 50 % .