The mean improvement in percent-expected peak flow for the experimental and control groups was 12.3 % ( 95 % CI , 9.1-15 .5 % ) and 13.8 % ( 95 % CI , 9.8-17 .9 % ) , respectively , with a mean difference of 1.5 % ( 95 % CI , -3.6 to 6.6 % ) .