Title: Method for controlling the washing step in a blood centrifugation cell
Abstract: A method and apparatus for controlling the washing step in a blood centrifugation cell in which washing solution is introduced into the blood centrifugation cell and the cell contains compacted red cells and supernatant at the beginning of the washing step. The apparatus can comprise various sensors and a computer. The sensors sense and transmit to the computer three inputs. The first input is indicative of the total volume of blood that enters the cell during the filling step and the total amount of washing solution that enters the cell during the washing step. The second input is indicative of the hematocrit value of the blood introduced during the filling step. The third input is indicative of the geometric characteristics of the cell. Based on the inputs, the computer executes an algorithm that produces a first output that is the concentration of the supernatant in the supernatant-washing solution mixture.
Patent Number: 7,001,323 Issued on 02/21/2006 to Panzani, et al.
| Inventors:
|
Panzani; Ivo (Mirandola, IT);
Romagnoli; Sergio (Castenaso, IT);
Belloni; Massimo (Isola Della Scala, IT)
|
| Assignee:
|
Dideco S.r.l. (Mirandola, IT)
|
| Appl. No.:
|
805086 |
| Filed:
|
March 19, 2004 |
Foreign Application Priority Data
| Apr 30, 2001[IT] | MI2001A0899 |
| Current U.S. Class: |
494/37; 210/739; 210/787 |
| Current Intern'l Class: |
B04B 13/00 (20060101) |
| Field of Search: |
494/1,5-6,10-11,37,41,42,43,45
604/401,501,611
210/104,143,782,787,87,961,739
|
References Cited [Referenced By]
U.S. Patent Documents
| 4919817 | Apr., 1990 | Schoendorfer et al.
| |
| 5298171 | Mar., 1994 | Biesel.
| |
| 5311908 | May., 1994 | Barone et al.
| |
| 5379775 | Jan., 1995 | Kruse.
| |
| 5383911 | Jan., 1995 | Mann.
| |
| 5385539 | Jan., 1995 | Maynard.
| |
| 5387174 | Feb., 1995 | Rochat.
| |
| 5417715 | May., 1995 | Noren et al.
| |
| 5423738 | Jun., 1995 | Robinson et al.
| |
| 5607579 | Mar., 1997 | Latham, Jr. et al.
| |
| 5730883 | Mar., 1998 | Brown.
| |
| 5876611 | Mar., 1999 | Shettigar.
| |
| 5919125 | Jul., 1999 | Berch.
| |
| 6241649 | Jun., 2001 | Zanella et al.
| |
| 6299784 | Oct., 2001 | Biesel.
| |
| 6352499 | Mar., 2002 | Geigle.
| |
| 6416456 | Jul., 2002 | Zanella et al.
| |
| 6605028 | Aug., 2003 | Dolecek.
| |
| 6629919 | Oct., 2003 | Egozy et al.
| |
| 6716151 | Apr., 2004 | Panzani et al.
| |
| 2003/0181305 | Sep., 2003 | Briggs et al.
| |
| 2005/0054508 | Mar., 2005 | Panzani et al.
| |
| Foreign Patent Documents |
| 0 682 953 | Nov., 1995 | EP.
| |
| 0 931 554 | Jul., 1999 | EP.
| |
| 0 931 554 | Jul., 1999 | EP.
| |
| 1254675 | Nov., 2005 | EP.
| |
| WO 98/2914/9 | Jul., 1998 | WO.
| |
Other References
US 6,348,030, 02/2002, Zanella et al. (withdrawn)
Gilbert et al., "Hematocrit Monitor," Critical Care Medicine, 17(9):929-933
(Sep. 1989).
Steinke et al., "Role of Light Scattering in Whole Blood Oximetry," IEEE Transactions
on Biomedical Engineering, BME-33(3):294-301 (Mar. 1986).
Zdrojkowski et al., "Optical Transmission and Reflection by Blood," IEEE Transactions
on Biomedical Engineering, BME-17(2):122-128 (Apr. 1970).
|
Primary Examiner: Cooley; Charles E.
Attorney, Agent or Firm: Popovich, Wiles & O'Connell, P.A.
Parent Case Text
This application is a continuation of U.S. Ser. No. 10/125,995, filed Apr. 19,
2002, now U.S. Pat. No. 6,716,151 issued Apr. 6, 2004, the contents of which are
hereby incorporated by reference herein.
Claims
What is claimed is:
1. A method for centrifuging blood in a filling step and controlling a washing
step in a blood centrifugation cell wherein blood is introduced into the blood
centrifugation cell in the filling step and washing solution is introduced into
the blood centrifugation cell in the washing step, the method comprising:
providing a blood centrifugation cell, a pump for communicating liquid to the
blood centrifugation cell, and a computer configured to receive data and produce
at least one output;
introducing blood into the blood centrifugation cell during the filling step;
centrifuging the blood so the cell contains compacted red blood cells and supernatant
at the beginning of the washing step,
providing first input data to the computer indicative of the total volume of
liquid that has entered the cell during the filling step that precedes the washing
step and during the washing step itself, the liquid being blood during the filling
step and the liquid being washing solution during the washing step;
providing second input data to the computer indicative of the hematocrit value
of the blood that was introduced during the filling step;
providing third input data to the computer indicative of the geometric characteristics
of the cell;
processing the first, second, and third input data in the computer to produce
a first output, said first output being the concentration of the supernatant in
the supernatant-washing solution mixture that is present in the cell during the
washing step, said first output being produced by the computer executing an algorithm
that expresses the supernatant extinction law inside the cell using the first,
second, and third input data; and
stopping the washing step when a certain concentration of supernatant in the
supernatant-washing solution is reached.
2. The method of claim 1, wherein the algorithm has time as a fourth input data.
3. The method of claim 1, wherein the algorithm that expresses the supernatant
extinction law inside the cell is derived from a mathematical model.
4. The method of claim 1, wherein the algorithm that expresses the supernatant
extinction law inside the cell is derived from an experimental analysis.
5. The method of claim 1, wherein the pump is a peristaltic pump comprising on
the drive shaft of the pump a sensor suitable to transmit to the computer said
first input data related to the rotation angles of said drive shaft.
6. The method of claim 1, further comprising providing a sensor for measuring
the volume of liquid entering the cell and suitable to transmit to the computer
said first input data.
7. The method of claim 1, further comprising providing a sensor for measuring
the hematocrit value of the blood entering the cell during the filling step and
suitable to transmit to the computer said second input data.
8. The method of claim 1, further comprising providing an operator interface
for entering into the computer said second input data indicative of the hematocrit
value of the blood.
9. The method of claim 8, wherein said pump comprises an intake and a cardiotomy
reservoir is located at the intake for said pump, and wherein said data indicative
of the hematocrit value of the blood is determined by measuring a hematocrit value
of the blood in the cardiotomy reservoir.
10. The method of claim 1, further comprising providing an operator interface
for entering into the computer said third input data indicative of the geometric
characteristics of the cell.
11. The method of claim 1, further comprising providing a sensor for automatically
detecting the geometric characteristics of the cell and suitable to transmit to
the computer said third input data.
12. The method of claim 1, further comprising providing an operator interface
for displaying the concentration of the supernatant in the supernatant-washing
solution mixture.
13. The method of claim 12, wherein the operator stops the washing step when
a certain concentration of supernatant is reached.
14. The method of claim 1, further comprising providing a controller for stopping
the washing step when a certain concentration of supernatant in the supernatant-washing
solution is reached.
15. The method of claim 14, wherein the controller stops the washing step when
a preset value of the concentration of supernatant in the supernatant-washing solution
mixture is reached.
16. A method for centrifuging blood in a filling step and controlling a washing
step in a blood centrifugation cell wherein blood is introduced into the blood
centrifugation cell in the filling step and washing solution is introduced into
the blood centrifugation cell in the washing step, the method comprising:
providing a blood centrifugation cell, a pump for communicating liquid to the
blood centrifugation cell, and a computer configured to receive data and produce
at least one output;
introducing blood into the blood centrifugation cell during the filling step;
centrifuging the blood so the cell contains compacted red blood cells and supernatant
at the beginning of the washing step;
providing first input data to the computer indicative of the total volume of
liquid that has entered the cell during the filling step that precedes the washing
step and during the washing step itself, the liquid being blood during the filling
step and the liquid being washing solution during the washing step;
providing second input data to the computer indicative of the hematocrit value
of the blood tat was introduced during the filling step;
providing third input data to the computer indicative of the geometric characteristics
of the cell; and
processing the first, second, and third input data in the computer to produce
a first output said first output being the concentration of the supernatant in
the supernatant-washing solution mixture that is present in the cell during the
washing step, said first output being produced by the computer executing an algorithm
that expresses the supernatant extinction law inside the cell using the first,
second, and third input data.
17. A method for controlling a washing step in a blood centrifugation cell wherein
washing solution is introduced into the blood centrifugation cell in the washing
step, the method comprising;
providing a blood centrifugation cell, a pump for communicating liquid to the
blood centrifugation cell, and a computer configured to receive data and produce
at least one output;
providing first input data to the computer indicative of the total volume of
liquid that has entered the cell during the filling step that precedes the washing
step and during the washing step itself, the liquid being blood during the filling
step and the liquid being washing solution during the washing step;
providing second input data to the computer indicative of the hematocrit value
of the blood that was introduced during the filling step;
providing third input data to the computer indicative of the geometric characteristics
of the cell; and
processing the first, second, and third input data in the computer to produce
a first output, said first output being the concentration of the supernatant in
the supernatant-washing solution mixture that is present in the cell during the
washing step, said first output being produced by the computer executing an algorithm
that expresses the supernatant extinction law inside the cell using the first,
second, and third input data.
Description
FIELD OF THE INVENTION
The invention relates to blood centrifuges and in particular relates to a system
for controlling the washing step in a blood centrifugation cell.
BACKGROUND OF THE INVENTION
It is known that in some medical procedures, such as inter- and post-operative
autotransfusion, there is the need to separate the plasma from the red cells of
the blood aspirated from the operating area, so as to make them available for re-infusion
to the patient. It is also known that currently this procedure is performed in
centrifugation cells in which the blood is introduced by means of a peristaltic pump.
A centrifugation cell substantially comprises two bells which are mutually coaxial
and rigidly coupled, and the portion of space between them is connected to the
outside by means of two tubes, an inlet tube and an outlet tube, which are connected
to the bells by means of a rotary coupling. The two bells are turned about their
own axis, while the tubes are kept motionless.
The procedure provides for a first step for filling the cell, in which the blood
is introduced by means of the inlet tube. Due to the centrifugal force, the red
cells, which are the heaviest cellular components of blood, are propelled outward,
compacting against the wall of the outer bell. Other cellular components such as
white blood cells and platelets are arranged in a thin layer known as buffy coat
directly adjacent to the mass of compacted red blood cells. The separated plasma,
the remaining component of blood, is arranged in a layer which lies above the buffy
coat. The plasma, which contains various substances such as anticoagulant, free
hemoglobin and other substances from the operating field, will be referenced hereinafter
as "supernatant".
As filling continues, the buffy coat moves closer to the rotation axis, displacing
the supernatant toward the outlet tube of the cell. When the supernatant reaches
the outlet tube the supernatant flows out of the cell into an adapted collection bag.
The flow of the supernatant in the outlet tube continues until an optical detector
reports that the buffy coat has reached the outlet tube of the cell. At this point
the filling step has ended and the introduction of new blood into the cell ends.
The cell now contains compacted red cells and supernatant, which must be eliminated
since it cannot be re-infused to the patient together with the red cells.
The above-described filling step is followed by a washing step performed by means
of a washing solution which, when introduced into the cell, gradually takes the
place of the supernatant that is expelled. At the end of the washing step the cell
contains red cells and washing solution, i.e., substances suitable to be re-infused
to the patient. The contents of the cell are collected in a suitable bag in a third
step of the procedure, known as emptying.
Our attention is focused exclusively on the washing step, which is currently
performed in manners that are not entirely satisfactory. A first procedure adopted
in the background art provides for introducing in the cell a preset amount of washing
solution at a value that is assuredly more than sufficient to wash the supernatant.
The consequent oversizing, however, wastes time and washing solution.
Another procedure used in the art provides a transparency sensor on the outlet
duct. However, this sensor is not able to detect the passage of transparent components
of the supernatant such as the anticoagulant, and therefore does not provide entirely
satisfactory results.
SUMMARY OF THE INVENTION
The invention provides a system for controlling the washing step in which the
washing step can be stopped when the intended result is reached. The present invention
provides a method for controlling a washing step in a blood centrifugation cell
wherein washing solution is introduced into the blood centrifugation cell in the
washing step, the cell containing compacted red blood cells and supernatant at
the beginning of the washing step. The method comprises: (1) providing a blood
centrifugation cell, a pump for communicating liquid to the blood centrifugation
cell, and a computer configured to receive data and produce at least one output;
(2) providing first input data to the computer indicative of the total volume of
liquid that has entered the cell during the filling step that precedes the washing
step and during the washing step itself, the liquid being blood during the filling
step and the liquid being washing solution during the washing step; (3) providing
second input data to the computer indicative of the hematocrit value of the blood
that was introduced during the filling step; (4) providing third input data to
the computer indicative of the geometric characteristics of the cell; (5) processing
the first, second, and third input data in the computer to produce a first output,
said first output being the concentration of the supernatant in the supernatant-washing
solution mixture that is present in the cell during the washing step, said first
output being produced by the computer executing an algorithm that expresses the
supernatant extinction law inside the cell using the first, second, and third input
data; and (6) stopping the washing step when a certain concentration of supernatant
in the supernatant-washing solution is reached.
In addition, the invention provides an apparatus for performing the method for
controlling the washing step in a blood centrifugation cell.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a blood centrifugation cell.
FIG. 2 is a diagram of an apparatus of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the figures, the reference numeral
1 generally designates
the blood centrifugation cell, which comprises inner bell
2 and outer bell
3, which are mutually rigidly coupled and are made to rotate in the direction
of the arrow in the figures. The numeral
4 respectively designates the inlet
tube to the portion of space comprised between the two bells. Peristaltic pump
5 pumps fluids into inlet tube
4. The fluids follow path
7
into region
10 between the inner and outer bells. Centrifugation separates
blood components, as described further below, and supernatant flows out of the
centrifuge via outlet tube
6. The inlet and outlet tubes are connected to
the assembly of the inner and outer bells by means of a rotary coupling, so that
they can remain motionless.
During the cell filling step, the red blood cells enter the cell along path
7 due to the action of the peristaltic pump
5, which is connected
at the suction to a container known as a cardiotomy reservoir
15. During
centrifugation, the red blood cells are compacted in region
8, and the supernatant
follows path
11 to the outlet tube
6. Buffy coat
9 separates
the compacted red blood cells from the supernatant in region
10. The supernatant
then flows toward the outlet tube
6 of the cell along the path
11.
When buffy coat
9, by moving increasingly closer to the rotation axis,
reaches the full level indicated by a sensor, the introduction of blood into the
cell ceases as pump
5 stops. Now the filling step has ended and cell
1
contains compacted red cells and supernatant.
This is followed by a washing step to eliminate the supernatant by means of
a washing solution. A preferred washing solution is physiological saline solution
(0.9 g/L NaCl in water). The washing solution is conveyed to cell
1 through
inlet tube
4 by pump
5, which is in communication with a reservoir
of washing solution.
The washing solution gradually takes the place of the supernatant, and at the
end of the washing step in cell
1, the replacement of the supernatant with
the washing solution has occurred substantially completely. A minute amount of
supernatant in cell
1 remains and will be reinfused to the patient. However,
small amounts of supernatant are obviously tolerable.
During the washing step, therefore, in the volume of the cell
1 that
is not occupied by the compacted red cells, there is a mixture of supernatant and
washing solution. The expression "supernatant concentration" is used to designate
the ratio between the volume of supernatant present in said mixture and the total
volume of said mixture, and it is immediately evident that the value of said concentration
varies during washing from the initial value of 1, when all the space available
is occupied by the supernatant, toward the ideal final value, which is zero and
would be reached if the supernatant were eliminated completely and fully replaced
by the washing solution. The expression "supernatant extinction law" is used to
designate the law that regulates the variation of the concentration of supernatant
in the supernatant-washing solution mixture as it decreases from the initial value
of 1 toward the final value.
The control system includes sensor
12, which is suitable to provide the
hematocrit reading of the blood entering the cell during the filling step, encoder
or sensor
13 on the driving shaft of the peristaltic pump
5, which
detects data related to the rotation angles of said shaft, and computer
14.
The computer executes an algorithm, derived from a mathematical model or from
the processing of experimental data, that expresses the supernatant extinction
law within cell
1 and has three inputs and one output.
The first input comprises the volume of the liquid that enters the cell during
the filling step, which is blood, and during the washing step, which is washing
solution. This first input is provided, in the described embodiment, by the encoder
13. The data it transmits to the computer
14 related to the rotation
angles gradually covered by the pump
5 are converted, since the characteristics
of said pump and of the tube
4 are known, into data related to the volume
of liquid progressively conveyed. However, clearly the encoder
13 might
be replaced with any liquid flow measurement instrument.
The second input comprises the hematocrit reading of the blood entering cell
1 during the filling step, and is provided by sensor
12, which reports
to computer
14 the hematocrit reading of the individual small volumes of
blood that enter cell
1 continuously. The second input might be provided
in other forms. For example, the computer
14 could include an operator interface
which allows entering into the computer
14 data related to the hematocrit
value of the blood, which can be determined from the cardiotomy reservoir located
at the intake of the pump
5.
The third input comprises the geometric characteristics of the cell. Accordingly,
there are means that allow the operator to enter into computer
14 data related
to these characteristics. Alternatively, a sensor
16 could be provided for
automatic detection of said characteristics.
On the basis of the three listed inputs, computer
14 provides an output
at each instant of the value of the concentration of supernatant in the supernatant-washing
solution mixture that is present in the cell
1 during the washing step.
In addition, it is possible to provide time as a fourth input.
The invention includes means that allow stopping the washing step when the intended
conditions are reached. In the described embodiment there is the display
14a,
which shows at each instant the value of the concentration of supernatant and thus
allows the operator to intervene and turn off the pump
5 when said value
reaches the threshold deemed acceptable. According to a different embodiment, there
is a controller to stop automatically the operation of the pump
5 when said
concentration reaches the threshold value that is preset as acceptable.
Various modifications and alterations to this invention will become apparent
to those skilled in the art without departing from the scope and spirit of this
invention. It should be understood that this invention is not intended to be unduly
limited by the illustrative embodiments and examples set forth herein and that
such examples and embodiments are presented by way of example only with the scope
of the invention intended to be limited only by the claims set forth herein as follows.
*
