Method of washing secondary filter in process for filtering plas

Details Method of washing secondary filter in process for filtering plas Method of washing secondary filter in process for filtering plas

1994-09-19

1996-05-14

Bhat, N.

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

210650, 210741, 210791, 210798, 210805, 604 5, 604 6, B01D 1100, B01D 6100, C02F 144

Patent

active

055164315

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a method of washing a secondary filter in a process for filtering plasma.


BACKGROUND ART

The plasma filtration processes include so-called double filtration plasmapheresis by which the substance to be removed is selected according to the pore size of a secondary filter, and so-called cryofiltration for removing pathogenic substances from plasma by a secondary filter with cooling. In either of these processes, continued filtration of plasma tends to gradually clog the secondary filter, so that it is necessary to eliminate clogging in the course of filtration.
There are two methods of eliminating clogging; one is replacement of the secondary filter by another one, and the other is washing the secondary filter with physiological saline or the like. The latter is used generally since the secondary filter is expensive.
As a method of washing the secondary filter, it is already proposed to wash the filter with a wash liquor in an amount approximately equal to the priming volume of the filter to ten-odd times the volume when the filtration pressure has reached 60% of the withstanding pressure of the secondary filter (maximum pressure to withstand the filtration pressure with safety), for example, 300 mm Hg (e.g., Tetsuzo Agishi et al., "Double Filtration Plasmapheresis," published by Igaku Shoin). However, the conventional washing method which consumes a large amount of wash liquor approximately equal to the priming volume to ten-odd times the volume gives rise to the problem of resulting in a greatly reduced filtration efficiency to necessitate much time for removing the pathogenic substance from plasma because every time the secondary filter is washed, the interior of the filter is entirely replaced by the wash liquor with the cake almost completely washed away by washing. The term filtration efficiency as used herein refers to the rate of removal of the substance per unit time. For example, in the case of cryofiltration wherein usually 2 to 4 liters of plasma needs to be treated in circulation, the time taken is as long as about 4 hours in total including the time required for washing the secondary filter, and the patient must be placed under restraint during this period. It is desired to shorten the time.


DISCLOSURE OF THE INVENTION

The main object of the present invention is to provide a method of washing a secondary filter in a process for filtering plasma, the method being adapted to shorten the time required for the filtration of plasma.
Another object of the present invention is to provide a method of washing the secondary filter in the plasma filtration process with a reduced amount of wash liquor and consequently with a diminished disposal loss of plasma from the system.
Other features of the present invention will be made apparent from the following description.
In a plasma filtration process including a treatment with a primary filter for separating blood into blood cells and plasma and a treatment with a secondary filter for removing harmful macromolecules from the separated plasma for purification, the present invention provides a method of washing the secondary filter characterized in that the secondary filter is washed by passing a wash liquor through an inner chamber of the filter, an outer chamber thereof or both the chambers in an amount corresponding to 5 to 50% of the priming volume of the filter every time the filtration pressure has reached 70 to 100% of the withstanding pressure of the secondary filter.
As a preferred mode of the present invention, the secondary filter is washed by passing the wash liquor through the inner chamber of the filter, the outer chamber thereof or both the chambers in an amount corresponding to 5 to 15 % of the priming volume of the filter every time the filtration pressure has reached 80 to 90% of the withstanding pressure of the secondary filter.
In the present invention, the withstanding pressure of the secondary filter means the maximum pressure at which the secondary filter is capable of withstanding t

REFERENCES:
patent: 4919817 (1990-04-01), Schoendorfa et al.
patent: 4936980 (1990-06-01), Yoshimichi et al.
patent: 5186835 (1993-02-01), Masuoka et al.
patent: 5242384 (1993-09-01), Robinson et al.
patent: 5261876 (1993-11-01), Popovich et al.
patent: 5298016 (1994-03-01), Gordon
patent: 5314624 (1994-05-01), Kawakura et al.
International Search Report Appln. No. PCT/JP94/00085, dated Mar. 18, 1994.

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