In the two treatment groups , pulmonary functional parameters , forced vital capacity ( FVC ) , forced expiratory volume in 1 second ( FEV1 ) , maximal voluntary ventilation ( MVV ) , peak expiratory flow ( PEF ) , forced expiratory flow at 25 % of forced vital capacity ( FEF25 ) , forced expiratory flow at 50 % of forced vital capacity ( FEF50 ) , and forced expiratory flow at 75 % of forced vital capacity ( FEF75 ) were determined .