Extracorporeal device and method for removal of secondary membrane

A method of blood treatment comprising:

• providing an extracorporeal blood treatment device comprising a dialyzer having a blood chamber, a dialysate chamber, and a semipermeable membrane, the blood chamber and the dialysate chamber being divided from one another by the semipermeable membrane, the dialysate chamber comprising a dialysate outlet valve;
• treating blood in a first operating mode by pumping dialysate through the dialysate chamber with a dialysate pump, pumping the blood through the blood chamber with a blood pump, and pulling ultrafiltrate out of the dialysate chamber with an ultrafiltrate pump;
• detecting factors that accelerate a build-up of a secondary membrane on the semipermeable membrane while treating the blood in the first operating mode;
• and
• switching from the first operating mode to a second operating mode, the second operating mode comprising closing the dialysate outlet valve for a duration of time and shutting off the ultrafiltrate pump, wherein
• the closing of the dialysate outlet valve prevents dialysate from flowing out of the dialysate chamber and causes a volume of dialysate to pass from the dialysate chamber to the blood chamber through the semipermeable membrane, and
• the switching from the first operating mode to a second operating mode upon detecting the factors that accelerate a build-up comprises switching at the expiration of a time interval before backflush calculated according to Equation II:
• Ti=(TB·Rn·Qs·Quf·Qb·Xd·Pv·Ptm)+Modx Equation II
• or Equation III:
• Ti+1=(TB·Rn·Qs·Quf·Qb·Xd·Pv·Ptm)+(−((Ti−TEi)·(1−XA)))+Modx Equation III
• or Equation IV:
• Ti+1=(TB·Rn·Qs·QufQb·Xd·Pv·Ptm)+((Ti−TEi)·((2−YAold)*YAnew))−(Ti−TEi))+(−((Ti−TEi)·(1−XA))+Modx Equation IV
• wherein Ti+1 is a newly calculated time interval before a backflush, Ti is an originally calculated time interval before a backflush, TB is a base time, Rn is a run number coefficient of modification (cm), Qs is a cm based on a substitution fluid rate and whether substitution fluid is introduced to the blood before the dialyzer or after the dialyzer, Quf is a cm based on a UF rate, Qb is a cm based on blood flow rate, Xd is a cm based on the dialyzer, Pv is a cm based on venous pressure, Ptm is a cm based on transmembrane pressure, TEi is an elapsed time since initiation of a current first operating mode, Modx is a sum of discrete modifiers to be taken into consideration, XA is an additionally applicable coefficient of modification, YAold is a previously applicable coefficient of modification Rn, Qs, Quf, Qb, Xd, Ptm, and Pv that is observed to have changed, and YAnew is a newly applicable coefficient of modification.