Blood Plasma Separator With Filter

Abstract

A piston having spaced resilient annular seals and filter material disposed about the piston between the spaced seals is adapted to be inserted into an open end of a collection tube so that the resilient seals engage the interior surface of the tube and form a seal on each side of the filter material which also contacts both the piston and the interior of the tube. The collection tube is adapted to receive blood for separation into its light and heavy phases. A pusher is detachably connected to the piston for allowing the piston to be pushed in a downward direction through the light phase of the blood so that a pressure is created below the piston which causes the resilient seals to temporarily deform and leak, thereby allowing the light phase to flow in an upward direction around the piston and through the filter material into a space above said piston. When the piston reaches an interface between the light and heavy phases the downward movement is terminated and the push rod is withdrawn after being detached from the piston. The piston remains in place as a permanent barrier between the light and heavy phases of the blood contained in the collection tube. A stopper is provided to be inserted into the open end of the collection tube so that the separated phases of the fluid may be shipped or stored in the collection tube for future laboratory tests.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to apparatus for separating the phases of blood and more particularly to an apparatus for separating blood serum or plasma from cellular material and for filtering the serum or plasma that is separated from the cellular material.

2. Description of the Prior Art

In normal practice a blood sample is withdrawn from a patient by the use of an evacuated collection tube such as a VACUTAINER tube manufactured and sold by Becton, Dickinson and Company. The cellular portion of the blood including white blood cells, red blood cells and platelets may be separated from the blood serum by the use of a centrifuge in which the tube is rotated, for example, at approximately 2,800 revolutions per minute for a period of 10 minutes. After centrifuging, the serum or plasma is completely separated from the cellular material and a distinct interface is observed. However, within a short time thereafter interaction between the liquid phase and the cellular material of the blood begins to occur and such interaction has an undesirable effect on tests that are to be subsequently performed on both the liquid phase and the cellular material.

Most prior art devices required that the serum or plasma be removed from the collection tube immediately after separation and transferred to another container. This procedure required considerable time and also increased the possibility of contamination of the blood sample. The procedure also necessitated the use of two separate containers for a single sample and therefore increased the risk of mismarking or loss of the true identity of the blood sample especially where large numbers of blood tests were performed simultaneously. Transfer of the serum or plasma also increased the possibility of spillage and the resultant exposure of laboratory personnel to infection from diseased blood. The prior art procedure was more expensive since it required the use of an additional container.

Thus, there was a need for an apparatus for providing a physical separation between the serum or plasma and the cellular material of the blood. The physical separation had to be inserted without unduly disturbing the interface between the separated phases of the blood while being sufficiently sturdy to allow for transportation of the container by mail without movement of or leakage around the separation device.

Many modern clinical laboratories are equipped with automatic blood analyzing devices and heretofore these devices have experienced difficulty with clogging because of the presence of fibrin suspended in the serum or plasma phase of the blood. It therefore became desirable that the serum or plasma be filtered to remove the suspended fibrin or other particles.

SUMMARY OF THE INVENTION

The present invention contemplates a manually inserted serum-plasma separator that includes a filter for removing particles from the separated serum or plasma. The separator is designed for insertion into a collection tube similar to the VACUTAINER type of blood collection tube sold by Becton, Dickinson and Company. The separator comprises a piston having two spaced annular resilient seals. Filter material is disposed about the piston between the spaced seals. The seals and filter material are resilient and of such size that there is an interference fit with the interior surface of the collection tube to establish seals between the piston and the interior surface of the collection tube. A pusher is detachably connected to the top of the piston so as to provide a handle for inserting the piston into the collection tube and for allowing the piston to be forced in a downward direction through the collection tube.

In use the piston is inserted into the collection tube after a blood sample has been taken and separated into its light and heavy phases having a distinct interface therebetween. The piston is then pushed downwardly through the light phase until it reaches a point just above the interface. The downward movement of the piston creates a pressure below the piston which causes the resilient seals to temporarily deform and leak thereby allowing the serum or plasma phase to flow in an upward direction about the piston and through the filter material into the space above said piston. When the bottom of the piston reaches a point just above the interface the downward movement is terminated and the pusher is detached from the piston and removed from the collection tube. A stopper may then be inserted in the open end of the collection tube so that the separated blood sample may be shipped or stored in the collection tube for later use.

The piston, because of the interference fit, remains as a permanent barrier between the serum or plasma and the cellular material of the blood so that the separated blood sample may be shipped or stored for future laboratory tests. The serum or plasma that passes through the filter material is essentially free of fibrin strands so that the serum may be analyzed in automated testing equipment without fear of clogging the equipment. The piston is easily inserted into the collection tube by the use of the attached pusher so that the piston is not contaminated by foreign material transferred from the fingers of the user. The piston may be readily pushed through the serum or plasma phase by the use of the pusher which may be easily removed from the piston so that the container may be resealed for storage or shipment.

The primary objective of the present invention is to provide an apparatus for permanently separating the serum or plasma phase of blood from the cellular phase.

Another objective of the present invention is to provide a permanent barrier between the separated phases of blood in the original collection tube without the need for transferring a phase to another container.

Another objective of the present invention is to provide a serum-plasma separator that filters the separated serum or plasma.

Another objective of the present invention is to provide an apparatus in which a blood sample may be collected, separated and stored or shipped for subsequent testing.

Another objective of the present invention is to provide a separator that may be manually inserted into the original blood collection tube for separating a centrifuged blood sample.

Another objective of the present invention is to provide a separator that requires low insertion force so as not to disturb the interface of the separated blood elements.

The foregoing objectives and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings, wherein one embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustrative purposes only and are not to be considered as defining the limits of the invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a collection tube filled with blood separated into its light and heavy phases.

FIG. 2 shows a separator assembly including a pusher adapted for insertion into the collection tube of FIG. 1.

FIG. 3 shows the separator assembly of FIG. 2 being inserted into the collection tube of FIG. 1.

FIG. 4 shows the pusher being removed from the collection tube of FIG. 3 while the separator remains in place.

FIG. 5 shows the collection tube of FIG. 4 with the pusher completely removed and a stopper placed in the open end of the collection tube.

DESCRIPTION OF THE INVENTION

Referring to FIG. 1 there is shown a collection tube 10 such as a VACUTAINER type collection tube sold by Becton, Dickinson and Company. Tube 10 contains blood which has previously been separated into a light phase 11, which may be serum or plasma, and a heavy phase 12 containing cellular material such as red blood cells, white blood cells and platelets. A distinct interface 20 is visible between the separated phases.

Referring now to FIG. 2 there is shown a separator assembly having a pusher indicated generally as 13 formed of plastic or other suitable material. The pusher may be formed in many different configurations, as an example the configuration shown in FIG. 2 has a substantially flat disc top portion 14 and an intermediate stem portion 15 having an X cross-section which terminates at its lower end in a second disc portion 16. Embedded in the lower end is a needle 17 which is positioned along a central axis of the pusher. The needle which is preferably made of stainless steel has a point 18 that is inserted into the center of the top of a resilient piston 19.

The needle is used to detachably connect the piston to the pusher so that the piston may easily be picked up, using the top portion 14 as a handle, for insertion into the open end of the collection tube without the fingers of the user touching the piston itself. This configuration is important since it prevents any foreign matter or perspiration from the user's fingers from contaminating the piston and thereafter contaminating the serum or plasma contained in the collection tube. The analytical tests that are performed on the serum or plasma are extremely sensitive and the slightest amount of contamination can easily lead to erroneous test results. In particular, the tests for sodium may be affected by the sodium chloride in perspiration from the user's hand.

Piston 19 includes two annular resilient sealing rings 22 and 23 formed integrally therewith for effecting seals between the piston and the interior surface of the collection tube 10. The rings are formed of sufficient size so that they have an interference fit with the interior surface of tube 10. The sealing rings are preferably disposed at an angle so as to lie in a conical surface having a vertex below the piston. Using this seal configuration the piston may be easily slid in a downward direction for insertion into the collection tube. The rings are formed of sufficient thickness so that they will begin to leak when subjected to a predetermined pressure.

A resilient filter sleeve 24 is disposed about the piston and between the sealing rings 22 and 23. The filter sleeve should be formed of a resilient material so that the filter material will engage both the piston and interior surface of the tube and form a seal therebetween. The thickness of the filter sleeve must be somewhat larger than the space between the piston and the interior surface of the tube so that the sleeve is slightly compressed when inserted into the collection tube. Several materials may be used for the filter sleeve such as felt, knitted wool or woven cloth. Another form of filter could be made by depositing a circular band of long strand flock onto a tacky adhesive surface of the piston, provided the adhesive is of a type that would not have an undesirable chemical reaction with the blood serum or plasma. A filter could also be provided by extruding polyurethane foam in a tubular configuration so that it could be stretched and slipped over ring 23 and placed around piston 19. The foam may be a type that has inter-connected cells.

In use, the collection tube 10 is provided with a blood sample in the conventional manner and the sample is then separated into its light and heavy phases to develop an interface as shown in FIG. 1. The separator assembly is picked up by the disc portion 14 and the piston is inserted into the open top of the collection tube 10. The piston is moved in a downward direction by applying a force to disc 14 in a direction as shown by arrow 26 in FIG. 3. Since the light phase 11 is liquid and incompressible the downward force exerted on the piston causes a pressure to be exerted by the liquid on the seals formed by the sealing rings 22 and 23. When the force is sufficient to establish the predetermined pressure the sealing rings begin to leak and allow the serum or plasma to flow in an upward direction between the piston and the interior surface of the collection tube. As the serum or plasma flows upwardly the piston moves downwardly through the serum or plasma as best shown in FIG. 3. The serum or plasma flows through filter 24 so that foreign particles and strands or portions of fibrin are removed from the separated serum or plasma. The piston is pushed downwardly to a position just above interface 20 at which position the downward force is terminated. The sealing rings again engage the interior surface of the collection tube and a permanent barrier is formed between the light and heavy phases.

An upwardly directed force is then exerted on the pusher 13 as shown by an arrow 27 in FIG. 4. The interference fit between the rings and the collection tube creates a greater frictional force than that between the needle and the piston and as a result the piston remains in place while the needle point 18 is pulled out of the resilient piston. The interference fit between rings 22 and 23 and the interior surface of the tube causes the piston to remain in position as a permanent barrier between the filtered serum or plasma and the cellular material.

It is to be noted that any other means may be used to detachably connect the pusher to the top of the piston. For example, a spherical bead like tip could be molded to the lower end of the pusher and a matching spherical cavity could be formed in the center of the top surface of the resilient piston 19. The pusher and the piston could be snapped together during manufacture and when the pusher is withdrawn the suction below the piston would hold it in place while the resiliency of the piston would allow the cavity in the top of the piston to yield permitting withdrawal of the pusher.

It is also contemplated that the piston could be formed of a non-resilient material such as hard rubber, plastic or metal. In such an embodiment the pusher could be threaded into the piston or detachably connected by other means familiar to the art. When a non-resilient piston is used the resilient annular seal rings must be mounted on the piston. The rings may be mounted by inserting them in grooves formed in the piston or the rings could be adhesively attached to the piston.

The use of two annular rings is preferred since they cooperate to hold the filter sleeve in place; however, it is to be understood that a single ring could be used provided the filter is held in place by other means.

After the pusher 13 is removed, stopper 25 shown in FIG. 5 may be inserted in the open end of the collection tube so that the separated blood components may be stored or shipped to a laboratory for analysis.

The invention has been described in its preferred embodiment using a filter sleeve around the piston. Other embodiments are contemplated wherein only a portion of the annular seal is designed to leak at a predetermined pressure. In such an embodiment the filter need only be disposed adjacent the portion of the seal that leaks so as to filter the serum passing the seal. In such an embodiment the filter would not be an annular sleeve and would therefore be attached to the piston by a suitable adhesive.

Thus, the present invention provides an inexpensive device for filtering and permanently separating serum or plasma from the cellular portion of a blood sample. The separated sample may be stored or shipped for subsequent testing. The separator device may be used in the original collection tube and therefore eliminates the need for a second container and also eliminates the time required to transfer a portion of the blood into the second container. The risk of contamination and misidentification of the blood sample is substantially reduced by eliminating the need for the second container. The filter portion of the separator removes fibrin or other particles from the separated serum or plasma so that the original collection tube may be inserted directly into automatic blood analyzing equipment without fear of clogging the analyzer. By providing a removable pusher the container may be sealed so that the blood sample may be stored or shipped without fear of the separated components interacting with each other or being mixed together during shipment.

Claims

What is claimed is:

1. An apparatus for effecting a seal between separated light and heavy phases of blood and for filtering the separated light phase, comprising:

a collection tube having an open end adapted to receive a sample of blood for separation into light and heavy phases wherein the heavy phase precipitates at the bottom of the collection tube and the light phase accumulates above the heavy phase;

a member adapted for insertion into the open end of the collection tube;

resilient seal means associated with said member for engaging an interior surface of said collection tube and for forming a seal between the member and the tube;

means for inserting said member into the open end of the collection tube and for exerting a force on the member to urge the member into the collection tube, whereby a pressure is developed in the tube, said resilient seal means being responsive to the pressure to deform and leak; and

filter means disposed adjacent said seal means, said filter means being formed and arranged to filter any fluid leaking past the seal means so that when the member is urged into the collection tube containing a separated blood sample the seal means leaks allowing the light phase to flow past the seal and through the filter and upon termination of the force a seal is effected between the filtered light phase and the remainder of the sample.

2. An apparatus as described in claim 1, wherein the resilient seal means is disposed about said member for engaging the interior surface of said collection tube and for forming an annular seal.

3. An apparatus as described in claim 1, wherein the member is in the form of a piston and the resilient seal means comprises a pair of spaced annular seals disposed about said member and the filter means is disposed between the spaced annular seals.

4. An apparatus as described in claim 3, wherein the piston and seals are resilient.

5. An apparatus as described in claim 1, wherein the resilient seal means is formed integrally with said member.

6. An apparatus as described in claim 3, wherein the pair of spaced annular seals are formed integrally with the member.

7. An apparatus as described in claim 6, wherein the annular seals are formed by outwardly extending rings.

8. An apparatus as described in claim 7, wherein the outwardly extending rings are disposed in a conical surface having a vertex positioned towards the bottom end of the tube.

9. An apparatus as described in claim 1, wherein the filter means is in the form of a sleeve disposed about said member.

10. An apparatus as described in claim 1, wherein the means for inserting said member into the open end of the collection tube comprises a pusher.

11. An apparatus as described in claim 10, wherein the pusher is detachably connected to the member.

12. An apparatus as described in claim 11, wherein the member is resilient and the pusher includes a needle extending from a lower end thereof and inserted into the member for detachable connection with said member.

13. An apparatus as described in claim 1, additionally comprising a stopper for closing the open end of the tube after effecting the sealed separation of the blood phases so that the separated blood may be stored or shipped to a laboratory for testing.

14. A separator apparatus for use with a blood collection tube to form a permanent barrier between separated light and heavy phases of blood contained in the collection tube, comprising:

a piston adapted for insertion into the collection tube;

resilient seal means disposed about said piston for engaging an interior surface of said collection tube and forming an annular seal between said piston and said interior surface, said annular seal being responsive to a predetermined pressure to temporarily deform and leak;

filter means disposed about said piston, and filter means formed and arranged to engage both said piston and the interior surface of said collection tube when said piston is inserted into said collection tube; and

means for inserting said piston into an open end of a collection tube and for exerting a force on said piston urging said piston into said collection tube.

15. An apparatus for effecting a seal between separated light and heavy phases of blood and for filtering the separated light phase, comprising:

a collection tube having an open end adapted to receive a quantity of blood for separation into light and heavy phases wherein the heavy phase precipitates to the bottom of the tube and the light phase floats above the heavy phase;

a member adapted to be inserted into the open end of the collection tube;

resilient sealing means associated with said member for forming a seal between the member and an interior surface of said collection tube when the member is inserted into the collection tube, at least a portion of said sealing means adapted to leak when subjected to a predetermined pressure;

filter means disposed adjacent the portion of the sealing means adapted to leak and between the member and the interior surface of the collection tube when the member is inserted into the collection tube said filter means being in sealing engagement with said member and the collection tube; and

means for inserting said member into the open end of the collection tube and for applying a force to said member to urge the member into the collection tube whereby a pressure exceeding the predetermined pressure is developed in the tube and the portion of the seal means caused to leak so that the light phase of separated blood contained in the tube flows past the seal and through the filter means as the member moves in a downward direction in response to the force applied thereto, and upon termination of the force the member stops and forms a permanent barrier between the filtered light phase above the member and the heavy phase below the member.

16. A separator apparatus for use with a blood collection tube to form a permanent barrier between the separated light and heavy phases of blood contained in the collection tube, comprising:

a member adapted to be inserted into the collection tube;

resilient sealing means associated with said member for forming a seal between the member and an interior surface of said collection tube when the member is inserted into the collection tube, at least a portion of said sealing means adapted to leak when subjected to a predetermined pressure;

filter means disposed adjacent the portion of the sealing means adapted to leak and between the member and the interior surface of the collection tube when the member is inserted into the collection tube, said filter means being formed and arranged to engage both said member and the interior surface of said collection tube; and

means for inserting said member into the collection tube and for exerting a force on said member for urging said member into said collection tube.