Blood collecting container and method

Abstract

Disclosed herein is an apparatus and method for obtaining accurate, consistent filling of an evacuated blood collecting tube under varying atmospheric pressure conditions. The apparatus comprises a gas-proof tubular container having one open end and one closed end; a gas-proof, elastomeric self-sealing closure to seal the open end; an elastomeric barrier-piston which forms a sliding-seal with the interior side walls of the container; and an indentation for preventing the piston from traversing the entire length of the container. The method of the invention comprises employing the apparatus of the invention in the collection of mammalian blood. The apparatus and method of the invention is particularly useful for the collection of blood with a simultaneous admixture of a chemical additive.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a method and apparatus for the collection of mammalian blood specimens and more particularly concerns an apparatus and method for the collection of an accurate measure of blood specimen from a mammal.

2. Brief Description of the Prior Art

The art is replete with descriptions of method and apparatus for the collection of mammalian blood for the purpose of diagnostic determinations. One of the most convenient methods for the collection of mammalian blood is within an air evacuated collection tube such as that described in U.S. Pat. No. 2,460,641. At the present time, however, identically evacuated blood collection tubes will draw varying amounts of blood in different parts of the world and on different days in the same geographic locality. This is due to atmospheric pressure variations (which can be a result of weather conditions or altitude differences). The accurate filling of evacuated blood collection tubes is most critical in blood collection tubes which contain a chemical additive for admixture with the collected blood specimen. For example, when the evacuated tube contains an anti-coagulant such as heparin. Too high or too low a blood to additive ratio may cause the blood sample to give inaccurate results in subsequent blood chemistry testing. This could ultimately lead to an error in analysis.

Prior hereto an apparatus and means for automatically collecting a measured amount of blood into an evacuated blood collection tube has not been available. The apparatus and method of my invention fills this long awaited need.

By the method and apparatus of my invention, it is now possible to collect almost automatically, an accurate measure of blood for clinical analysis. The collected blood may then be separated into its liquid and substantially cellular portions without transfer to a separate container for centrifuging. The apparatus of my invention is a unitary, simply constructed and economical unit which may be disposed of after a single use. The apparatus and method of my invention are readily employed by para-medical personnel having a minimum amount of training in accurate blood collection and analysis techniques.

SUMMARY OF THE INVENTION

The invention comprises an apparatus for the collection of an accurate measure of blood which comprises: a gas-proof tubular container having one open end and one closed end; a gas-proof, elastomeric, self-sealing closure to seal said open end; an elastomeric barrier-piston formed of an elastomeric material and which forms a sliding-seal with the interior side walls of said container; and means for preventing said piston from traversing the entire length of said container; provided that at least one of said closure and said piston has a recess in the surface thereof which is proximal to the other of said closure and said piston. The invention also comprises the method of collecting an accurate measure of blood employing the apparatus of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side elevation of an embodiment within the scope of the apparatus of the invention shown prior to its operation.

FIG. 2 is a cross-sectional side elevation of the embodiment seen in FIG. 1 but following its filling with blood.

FIG. 3 is a cross-sectional side elevation of the embodiment of the invention as seen in FIG. 2 but following its centrifugation to separate the collected blood into its light liquid component and its heavy, substantially cellular component.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus of the invention may be fabricated from conventional materials. Illustratively, the gas-proof container may be formed of glass. The gas-proof closures employed herein may be fabricated of any suitable elastomeric self-sealing materials. The preferred material for forming gas-proof closures is butyl rubber. The methods and techniques of assembling the apparatus of the invention will be obvious to those skilled in the art.

The apparatus of the invention and the method of the invention will now be further described and exemplified by reference to the various specific embodiments set forth in the drawings.

FIG. 1 is a cross-sectional side elevation of an apparatus of the invention referred to generally by the symbol 10. Apparatus 10 comprises a gas-proof tubular container member 12 having one end sealed with a gas-proof, penetrable closure 14 and a second end 13 which is sealed. Closure 14 is a member which may be termed a "stopper" which may be characterized by its cylindrical body portion 16 which is inserted under compression into the open end of container 12 so as to maintain container 12 in a sealed gas type engagement. Stopper 14 also has an enlarged head portion 18 to facilitate its insertion and removal. Body portion 16 of closure 14 has an annular recess 20 therein which together with axial recess 22 in head portion 18 forms a thin penetrable zone 24 in closure member 14. The thin penetrable zone 24 should have a minimum of at least 0.06 inches thickness when the elastomeric material of which stopper 14 is formed is butyl rubber. This minimum thickness assures that the apparatus 10 will maintain a vacuum for a period of at least 2 years. Nested beneath closure 14 is a piston-barrier member 30 which forms an interference-sliding fit with the interior walls 32 of container 12. Piston-barrier 30 as shown in FIG. 1 has a central cylindrical body portion 34 and integral upper sealing ring 36 and lower sealing ring 38 which form a sliding seal with the interior wall 32 of container 12. Within the central body portion 34 of piston-barrier member 30 there is an annular recess 35 which is provided as an alternate embodiment when it is desired to add chemicals 39 to the collected blood. The chemical additive is stored within annular recess 35 prior to the collection of blood. The volumetric area for annular recess 35 is sufficient to hold the chemical additive with a minimal amount of air space. The amount of air space above the piston has a direct bearing on the accuracy of the filling of the tube. The more space above the piston 30 initially, the less accurate is the filling procedure. A small amount of space is required to allow the needle room to penetrate the stopper, but such space should be minimal.

The apparatus of the invention as shown in the embodiment of FIG. 1 may be assembled under conditions of a partial vacuum so that chamber 40 of container 12 will have a partial vacuum contained therein. In practice, the vacuum employed is circa 26 millimeters of mercury.

The method of the invention is carried out by filling an evacuated apparatus of the invention 10 with blood, upon which analysis is desired. Referring now to FIG. 2 there is seen apparatus 10 which has been penetrated by cannula 35 through thin penetrable zone 24 of the closure 14. The open end of cannula 37 terminates within recess 20. Recess 20 should have a minimal volumetric capacity, i.e.; the minimum space required to allow the needle room to penetrate the stopper and receive an initial flow of blood. As blood 5 enters the axial recess 20, the pressure above piston-barrier 30 is increased over the pressure found in evacuated chamber 40. The pressure differential causes piston-barrier 30 to descend within container 12 while maintaining sealing engagement with the inner walls 32 of container 12. Piston-barrier 30 will descend within container 12 until it is stopped by constriction 44 which is integrally molded within the walls of container 12. Constriction 44 is a stop means positioned so that upper chamber 40A has a precise volumetric capacity as required for an accurate volumetric collection of blood. Alternatively, the stop means may be a force fit plastic ring inserted in the container at the desired point, or a tubular sleeve of specified length inserted in the lower end of the container. Upon striking stop means 44, piston-barrier 30 is halted and when the pressure in upper chamber 40A equals the pressure of incoming blood, the filling of container 12 with blood terminates and cannula 37 may be withdrawn whereupon the thin penetrable self-sealing zone 24 seals the opening previously made by cannula 37. When the annular recess 35 contains a chemical additive such as heparin, sodium oxalate, potassium oxalate or the like then the incoming blood 5 automatically admixes therewith to result in an accurate volumetric collection of blood in admixture with a precise amount of chemical additive previously enclosed within recess 35. That portion of the container represented by chamber 40B will contain residual air not evacuated during assembly of the apparatus 10. Piston-barrier 30 forms a permanent seal between this residual air and the collected blood so that the collected blood is not exposed to atmospheric gases.

Following collection of blood 5, the apparatus 10 may be centrifuged conventionally to effect a separation of the collected blood into its lighter liquid or plasma portion and its heavier substantially cellular portion.

FIG. 3 is a cross-sectional side elevation of a filled apparatus 10 shown following centrifugation wherein the blood has now been separated into its light liquid portion 5A and its substantially cellular portion 5B. To remove the light liquid portion for chemical analysis, one may remove closure 14 and remove by decantation or pipette the light liquid portion for chemical analysis.

Claims

What is claimed:

1. Apparatus for the collection of an accurate measure of blood which comprises:

a gas-proof tubular container having one open end and one closed end;

a gas-proof, elastomeric, self-sealing closure sealing said open end;

an elastomeric barrier-piston formed of an elastomeric material and which forms a sliding-seal with the interior side walls of said container;

means for preventing said piston from traversing the entire length of said container;

provided that at least one of said closure and said piston has a recess in the surface thereof which is proximal to the other of said closure and said piston, said recess providing only the minimum space required to allow the needle room to penetrate the stopper and receive an initial flow of blood; and

said apparatus having a partial vacuum in all chambers within said container.

2. Apparatus according to claim 1 wherein said self-sealing closure has a thin zone which is penetrable by a cannula.

3. Apparatus according to claim 1 wherein said piston has integral sealing rings in the side walls thereof for forming a seal with the interior walls of said container.

4. A method of collecting an accurate measure of blood which comprises:

A. providing an air-evacuated tubular container having one open end and one closed end;

a gas-proof elastomeric self-sealing closure sealing said open end;

an elastomeric barrier-piston formed of an elastomeric material and which forms a sliding-seal with the interior side walls of said container;

means for preventing said piston from traversing the entire length of said container;

provided that at least one of said closure and said piston has a recess in the surface thereof which is proximal to the other of said closure and said piston, said recess providing only the minimum space required to allow the needle room to penetrate the stopper and receive an initial flow of blood; said apparatus having a partial vacuum in all chambers within said container; and

B. filling said container by inserting a cannula into said recess, said cannula being attached to a source of blood.