Also , a higher increase in peak VO2 ( peak VO2 , 21.6 % ( 6.9 ~ 106.4 % ) vs 1.9 % ( -15.7 ~ 21.0 % ) in the placebo group , P = 0.04 ) and a larger decrease in ventilatory efficiency were observed in the udenafil group ( -6.4 9.7 vs 1.9 12.1 in the placebo group , P = 0.03 ) .