H i Nur,,,
ur question really is confusing,,,let me tell u one thing,,,my daughter gets 400 ml of blood at the same time,, a bag of 300 ml and 100 ml from another bag,, they never change the filter,, so i assume ur blood quantity is smaller i.e 200 ml total,, so i don think there is any need of changing filter,, i don know abt the filter brands ,, but they do it like here in pakistan,,but it's only my opinion,, i think u shud ask ur doc abt this,,
Take Care ..
Zaini.