Patent ID: 7588722

Claim:
A blood treatment device by extracorporeal circulation comprising: a filter having a primary chamber and a secondary chamber separated by a semi-permeable membrane, a blood circuit having an arterial line intended to draw blood from a patient, the filter's primary chamber and a venous line intended to return blood to the patient, a dialysate circuit comprising the filter's secondary chamber and at least one drain line for directing to a drain waste liquid coming from the filter's secondary chamber, a first bag in fluid communication with the drain line, a second bag in fluid communication with the drain line, at least one first gravimetric weighing means linked to the first bag, the drain line including: one conduit connecting the filter to the drain, said conduit being the only conduit connecting the filter to the drain; a first branch connecting the first bag to the conduit, said first branch being the only branch connecting the first bag to the conduit; a second branch connecting the second bag to the conduit, said second branch being the only branch connecting the second bag to the conduit; said first and second branches being the only elements connected to and in fluid communication with the conduit between the filter and the drain; the second branch being connected to the conduit upstream of the first branch according to the flow within the conduit; fluid flow rate adjustment means acting on the drain line comprising: a first adjustment organ acting upstream of the first and second bags, a second adjustment organ acting on the conduit between the first branch and the second branch; and a third adjustment organ acting downstream of the first and second bags, a control unit linked to the first gravimetric weighing means and to the fluid flow rate adjustment means, the control unit being configured to: control the first adjustment organ to ensure the presence of a substantially continuous flow rate during the treatment, receive weight signals from the first gravimetric weighing means and, control the fluid flow rate adjustment means to load one of the first and second bags with liquid while the other of the first and second bags unloads liquid, and vice-versa by using first and second threshold values determined by the first gravimetric weighing means wherein the first bag is placed lower than the second bag, such that the control unit is configured to load the first bag in priority with respect to the second bag, and unload the second bag into the first bag by gravity, by opening the second adjustment organ.