Cumulative tracheal colonization greater than @ ( @ ) cfu/ml at Day @ was as follows ( median -LSB- interquartile range -RSB- ) : cylindrical polyvinyl chloride , @ ( @-@ @ ) ; cylindrical polyurethane , @ ( @-@ @ ) ; conical polyvinyl chloride , @ ( @-@ @ ) ; and conical polyurethane , @ ( @-@ @ ) ( P = @ ) .