A press for driving a plasma layer and a buffy-coat layer in succession
out of a centrifuged whole blood bag which has upper and lower press
plates between which a clamping element is displaceable, all juxtaposed
with a stationary plate so that after displacement to the lower
press plate to drive off plasma and operation of the upper press
plate to spread the buffy-coat layer in height, the clamping element
can be actuated to clamp off the bag between the buffy-coat layer
and the red cell concentrate so that advance of the upper press
plate can drive off the buffy-coat layer.
1. An apparatus for decanting a blood plasma layer and a buffy-coat
layer in succession from a centrifuged blood bag having said buffy-coat
layer above a red cell concentrate and said plasma layer above said
buffy-coat layer in said bag, said bag having a tube at an upper
end thereof, said apparatus comprising:
a vertical stationary press plate mounted on said housing and positionable
against one side of said bag;
a lower movable press plate mounted between said housing and a
lower portion of said stationary press plate positionable along
an opposite side of said bag substantially encompassing a portion
thereof containing said red cell concentrate;
an upper movable press plate displaceable independently of said
lower press plate and mounted between said housing and an upper
portion of said stationary press plate positionable along said opposite
side of said bag above said lower press plate; and
a clamping element mounted on said housing and displaceable thereon
independently of said upper and lower press plate between said upper
and lower press plates for squeezing said bag against said stationary
press plate to define two compartments in said bag, one above and
one below the clamping element.
2. The apparatus defined in claim 1 further comprising means for
mounting said stationary press plate on said housing to enable it
to swing about a vertical axis and enable said bag to be accommodated
between said stationary press plate and said movable press plates,
and latch means for securing said stationary press plate in a position
in which it is substantially parallel to said movable press plates.
3. The apparatus defined in claim 2 wherein said upper press plate
is provided with an elastic cushion allowing it to compensate for
distortion of said bag.
4. The apparatus defined in claim 1 further comprising means for
imparting an initial partial stroke to said upper press plate and
thereby spread said buffy-coat layer in said bag in a vertical direction.
5. The apparatus defined in claim 1 further comprising a plurality
of pins extending from said housing for suspending said bag therefrom,
and means for vertically adjusting the level of said pins.
6. The apparatus defined in claim 1 further comprising an elastic
member on said stationary plate juxtaposed with said clamping element.
7. The apparatus defined in claim 1 further comprising means for
relieving a force on said lower press plate upon advance of said
8. The apparatus defined in claim 1 further comprising means for
sensing a blood plasma/buffy-coat interface for controlling said
9. The apparatus defined in claim 8 wherein said sensing means
includes a row of infrared light detectors paired with respective
infrared emitters across said bag.
10. The apparatus defined in claim 9 wherein said sensing means
is operated with pulsating light at a wavelength of 940 nm.
11. The apparatus defined in claim 10 further comprising means
for pulsing said light at a frequency of 68 Hz.
12. The apparatus defined in claim 11 further comprising means
for mounting said stationary press plate on said housing to enable
it to swing about a vertical axis and enable said bag to be accommodated
between said stationary press plate and said movable press plates,
and latch means for securing said stationary press plate in a position
in which it is substantially parallel to said movable press plates
13. The apparatus defined in claim 12 wherein said upper press
plate is provided with an elastic cushion allowing it to compensate
for distortion of said bag.
14. The apparatus defined in claim 13 further comprising means
for imparting an initial partial stroke to said upper press plate
and thereby spread said buffy-coat layer in said bag in a vertical
15. The apparatus defined in claim 14 further comprising a plurality
of pins extending from said housing for suspending said bag therefrom
and means for vertically adjusting the level of said pins.
16. The apparatus defined in claim 15 further comprising an elastic
member on said stationary plate juxtaposed with said clamping element
17. The apparatus defined in claim 16 further comprising means
for relieving a force on said lower press plate upon advance of
said clamping element.
FIELD OF THE INVENTION
Our present invention relates to an apparatus for the decanting,
successively, of an upper blood-plasma layer and an intermediate
buffy-coat layer through a flexible tube opening into the top of
a flexible bag containing blood which has been centrifuged to form
these two layers above the erythrocyte or red blood cell concentrate.
BACKGROUND OF THE INVENTION
It is known that the centrifugation of blood can separate the latter
into three distinct layers, namely a least-dense layer constituted
by the blood plasma and forming the upper layer, an intermediate
layer consisting predominantly of leukocytes and thrombocytes, known
as the buffy-coat layer and of intermediate density, and a lower
layer constituted predominantly of erythrocytes or in the form of
a red blood cell concentrate having the greatest density.
Separation of these layers is frequently desired so that, for example,
the plasma can be stored separately from the red cell concentrate,
the red cell concentrate can be processed into valuable blood products,
and/or the buffy-coat layer can be processed for a similar purpose
While the centrifugation of blood has been done in rigid vessels
or in centrifuges which separate the components in a continuous
manner, in recent years the collection of blood in flexible bags
has dominated and so too has the whole blood been increasingly centrifuged
in such bags which have flexible tubes opening into the upper ends
of the bags.
In order to decant the plasma and buffy-coat layers from such bags,
press arrangements have been provided which can have vertical press
plates between which the bag can be introduced and one of each is
advanced toward the other to drive the upper layer of plasma out
of the tube followed by the buffy-coat layer.
Such a press generally made use of a movable press plate which
was somewhat smaller in size than the stationary press plate and
which covered substantially the area of the red cell concentrate
so that by squeezing the latter inwardly, the layers above the red
cell concentrate can be effectively driven out of the tube.
A press of this type is described in U.S. Pat. No. 4350585 and
has experienced a problem at least with respect to the expulsion
of the buffy-coat layer from the blood collection bag. In this arrangement,
after the plasma is ejected by squeezing the red cell concentrate
with the relatively small movable press plate, all or part of the
buffy-coat layer tends to remain in the bag above this movable press
plate and must be expelled from the bag manually or by other manipulations
applied to the portion of the bag above the red cell concentrate.
In practically all cases some mixing of the low-density buffy-coat
layer with the red cell concentrate occurs and this is undesirable.
The successive removal of blood plasma and buffy coat from a blood
bag has also been described in Vox Sanguinis 39 (1980), 46-59 see
especially pages 48-51.
In this system after the blood plasma has been driven off above
the buffy coat, a clamp is applied to the bag between the buffy
coat and the red blood cell concentrate to allow the separation.
A stomach-operation clamp is used for this purpose.
The quality of the separation here as well is dependent upon the
manipulative skills of the individual.
OBJECTS OF THE INVENTION
It is the principal object of our present invention to provide
an improved apparatus for the decanting of a plasma layer and a
buffy-coat layer from a centrifuged whole blood bag whereby the
disadvantages of the earlier apparatus can be avoided.
Another object of this invention is to provide an improved apparatus
for the purposes described which is capable of automatically decanting
in succession the plasma and the buffy-coat layer from centrlfuged
whole blood in a flexible bag without manual manipulations which
may lead to mixing of the red cell concentrate and the buffy-coat
layer and in a substantially automatic and highly preclse manner.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter
are attained, in accordance with the invention, in a press apparatus
of the type described wherein, however, an upper press plate is
provided above the relatively small press plate previously described
and likewise is juxtaposed with the fixed press plate and which
is movable independently of the lower movable press plate so that
it covers substantially the balance of the bag and at least an upper
portion thereof, while between the upper and lower press plates,
a horizontally movable squeezing element is provided for clamping
the bag between itself and the stationary press plate.
Not only does this system integrate a clamp directly into the press,
but it provides a unique arrangement for ensuring that the buffy-coat
layer is fully decanted from the bag.
According to a feature of the invention, the upper and lower press
plates and the squeezing or clamping element are disposed on the
same side of the bag, preferably on the housing side thereof, so
they can be actuated by respective drives while the stationary plate
can be swingably mounted along one edge about a vertical axis and
provided with means on the housing which can lock the stationary
plate in position relative to the housing and to the movable plates.
This locking arrangement facilitates insertion and removal of the
Advantageously the upper press plate is provided with an elastic
cushion with the aid of which a compressing force is applied to
the upper movable press plate in the direction of the fixed press
Control means can be provided to enable the upper press plate to
be advanced before activation of the lower press plate with an adjustable
The bag can be suspended from pins which may be vertically adjusted,
i.e. adjusted as to height relative to the housing.
According to a feature of the invention the bag squeezing or clamping
element is juxtaposed with an elastic or resilient portion of the
opposing fixed press plate while the lower press plate can have
its actuating force relieved upon advance of the clamping element.
It has also been found to be important to control the advance of
the clamping element with the aid of a sensing source for the blood
plasma/buffy-coat interface, this sensing means being preferably
a horizontal row of infrared light emitters or source and a row
of infrared detectors spaced from the emitters across the transparent
bag and being located advantageously substantially at the level
of the upper movable press plate.
The infrared emitters and detectors are preferably designed to
operate with a pulsing infrared with a wavelength of 940 nm and
the pulsing frequency should be about 68 Hz.
A wavelength of 940 nm and a frequency of 68 Hz has been found
to be especially effective for the detection of the interface between
the buffy-coat layer and the plasma so that ambient effects are
eliminated, namely, the effects of daylight, room lighting, bag
distortion and the like.
BRIEF DESCRIPTION OF THE DRAWING
The above and other objects, features and advantages of the present
invention will become more readily apparent from the following description,
reference being made to the accompanying drawing in which:
FIG. 1. is a perspective view in highly diagrammatic form of an
apparatus in accordance with the present invention; and
FIG. 2 is a diagrammatic vertical section through this apparatus
in which the housing wall and structure have not been shown and
in which the drives for the movable parts and the controls therefor
have been illustrated only schematically.
The apparatus of the invention as illustrated in FIGS. 1 and 2
is intended to decant a plasma layer P overlying a buffy-coat layer
BC above a red cell concentrate layer RC in a bag B containing whole
blood which has been centrifuged to form the respective layers.
The flexible bag B is composed of transparent synthetic resin material,
i.e. is a blood-collecting bag, and is provided with an upper tube
T through which the layers can be driven out. A anticoagulant may
have been provided in the blood collecting bag before the commencement
of blood collection.
The apparatus for decanting the two upper layers from this bag
comprises a housing 5 upon which a press plate 1 is mounted by a
hinge 20 at a flange 21 rigid with this plate and along one vertical
edge thereof so that the plate 1 can swing about the vertical axis
A pair of swingable latches 7 on pedestals 22 can engage an opposite
longitudinal edge of the plate 1 when the latter is parallel to
the front wall 6 of the housing as shown in FIG. 1 to brace this
plate and hold it stationary during press operation.
Before the plate 1 is swung into the position shown in FIG. 1
the bag B seen in FIG. 2 but omitted in FIG. 1 is inserted against
the upper and lower press plates 3 and 2 respectively, which lie
on the housing side of the device.
The lower press plate 2 has an area such that it encompasses at
least the area containing the red cell concentrate RC of the bag.
The upper press plate 3 covers the remainder of the area of the
bag except for a portion between the two plates within which a clamping
element 8 is provided.
The clamping element 8 between the upper and lower press plates
3 and 2 is itself a horizontally movable horizontal plate and can
be displaced in the direction 23 (FIG. 2) to clamp the bag and define
two compartments one above and one below the clamping site C.
Within the housing 5 the plates 2 and 3 are provided with independent
drives 24 and 25 respectively constituted by fluid-operated cylinders
whose piston rods 26 and 27 are shiftable in opposite directions
and can displace the plates 2 and 3 independently to the left and
to the right. Preferably these drivers 24 and 25 are double-acting
A further double-acting hydraulic cylinder 28 has its piston rod
29 connected with the plate 8.
Although not visible in FIG. 2 it will be apparent that the press
plate 3 can be actuated via an elastic cushion 29 bonded to the
plate 3 and to a plate 30 to which the piston rod 27 is actuated.
This elastic cushion compensates for irregularities in the bag and
ensures a complete expulsion of the liquid contained in the upper
compartment between the clamping site C and the tube T.
As is also apparent from FIG. 2 the stationary plate 1 in its
region opposite the edge of the clamping plate 8 is provided with
an elastic cushion 31 which serves to prevent damage to the bag
by the clamping action.
At the level of the upper press plate 3 suspending pins 9 for
the centrifuged bag are provided As can be seen from FIG. 1 these
pins 9 can be provided in pairs so that bags of different sizes
can be accommodated or bags of different constructions can be used
in the system of the invention. The pins 9 are provided with means
enabling their heights to be adjusted Such means can include, as
is apparent from FIG. 2 a threaded spindle 32 which is journaled
on the housing, has a adjustment knob 33 and threadedly engages
a bar 34 to which the pins 9 are anchored.
To accommodate the vertical adjustability of the pins 9 the stationary
press plate 1 and the movable press plate 3 are provided with vertical
slits 35 and 36 respectively. Slits 35 and 36 are part of the combined
set of slits 10.
The clamping element 8 is controlled by a sensing device for the
blood plasma/buffy-coat interface, this sensing device being provided
heightwise in the region of the upper press plate 3 in the form
of a horizontally oriented row of infrared light emitters 11 and
detectors 12 which are energized with pulsating light at a frequency
of 68 Hz, the light having a wavelength of 940 nm.
These parameters have been found to eliminate detrimental effects
of daylight and room light upon the interface detection and further
enable the detector to be insensitive to writing on the bag and
An operating signal is triggered only when all three pairs of light
sources and light detectors 11 12 have the transmitted light reduced
by at least 80 % for at least 0.1 seconds
To spread the buffy coat in height, before the lower press plate
2 is actuated, the upper press plate 3 is advanced through a portion
of its stroke
To this end, each of the drivers 24 25 28 is provided with a
control valve shown only schematically at 37 38 and 39 the valves
being operated by a controller 40 which receives an input from the
stroke setter 41 to advance the movable plate 3 by this portion
of its total stroke initially
By corresponding setting of this partial stroke and the height
of the pins 9 practically all usual blood bags can be employed
in accordance with the invention since the clamping element 8 can
then be moved across the bag directly below the buffy-coat cell
concentrating interface to subdivide the bag at this interface.
When the clamping 8 is actuated, the lower press plate can be relieved
to enable the clamping element to achieve the clamping operation
as rapidly as possible.
Above the press, a tube clamp 13 is provided to hold the
tube in place (see U.S. Pat. No. 4350585) and the housing can
include the power supply and operating controls 14 including the
940 nm pulsed power supply for the infrared emitters The infrared
sensor input to the controller 40 has been represented at 42. An
auxiliary press for an auxiliary bag has been shown at 16 in FIG.
1 (see the discussion of satellite bags in the Vox Sanguinis article
cited) and additional clamping tube-welding or sealing heads 15
can be provided as diagrammatically represented at 15. With the
plate 1 swung open, the centrifuged blood bag is suspended on the
pins 9 and its tube T is lead through the tube clamp 13.
The free end of the tube can be connected via other tubes in the
clamping and welding heads 15 to two satellite for empty bags. The
plate 1 is then closed and latched at 7. The clamp 15 for the plasma
is opened while the clamp for the satellite bag for the buffy-coat
layer is closed
The upper press plate 3 is advanced through the aforementioned
portion of its stroke to drive at least a part of the blood plasma
into its satellite bag. The buffy-coat layer is thereby spread.
The lower press plate 2 is then advanced by the controller 40 to
drive off additional blood plasma and raise buffy-coat/plasma interface.
When this interface reaches the sensor pairs 11 12 the clamp 13
is closed. The clamping element 8 is automatically advanced in the
direction of arrow 23 and the force upon the lower press plate 2
is relieved. The buffy-coat layer is thereby separated from the
red cell concentrate.
If all of the plasma has been driven off or when all of the plasma
has been off, the clamp 15 seals off the connection with the plasma
bag and another clamp 15 for the buffy-coat satellite bag is opened.
The plate 3 continues its advance through the remainder of its
stroke to completely drive off the buffy-coat layer into its satellite
Using the auxiliary press 16 an auxilary fluid (SAGM) can be added
to the red cell concentrate layer through a respective branch tube
in one of the clamps 15. The press 16 can be operated with drivers
similar to those shown by the controller 40.
The lower press place 2 and the upper press plate 3 need not necessarily
be rigid or exclusively horizontally displaceable and indeed it
is possible to actuate these press plates by or form them as hydraulic
or pneumatically actuatable membranes within this invention.