Dual chamber syringe for collecting samples and blood collecting system

The dual chamber syringe is employed for collecting blood samples. The syringe includes a plunger which is connected to a first piston which, in turn, is connected via a string to a second piston. A passageway is formed in the wall of the syringe barrel to communicate the duct at the forward end of the barrel with the chamber between the two pistons. Thus, upon withdrawal of the plunger from a barrel, fluid flows into the chamber created between the two pistons. Subsequent movement of the two pistons in unison causes a whole blood sample to be drawn into the foremost chamber within the barrel. The syringe can be subsequently connected with a vacutainer via a needle assembly so as to discharge the whole blood sample into the vacutainer for subsequent testing procedures. The discard fluid can be separately dispensed into another container. A catch is employed on the syringe barrel or on the plunger to positively prevent a movement of the plunger into the barrel which would cause a discharge of the discard fluid.

This invention relates to a dual chamber syringe for collecting blood 
samples and to a blood collecting system. 
As is known, various types of techniques have been employed for the 
collection of blood from a patient. Generally, hospitals and homecare 
companies are now required to insure that precautions against occupational 
exposure to blood and other potentially infectious materials are followed 
by all employees in the healthcare setting, from the laboratory to the 
housekeeping department. Many of the precautions are based upon a belief 
that compliance with universal precautions will provide safeguards against 
transmission of various viruses and organisms such as HIV. 
One of the areas of concern in a healthcare setting is the possibility of a 
needlestick. This is because needlesticks are believed to present the 
greatest danger to nurses and lab personnel because of the variety of 
procedures involved in the drawing of blood from a patient. Thus, nurse 
safety is at risk each time a needle is used to sample or transfer blood, 
for example, to an evacuated tube. There is also a potential for exposure 
to dangerous pathogens each time when blood is extracted from a catheter. 
Patient safety is also threatened by the risk of catheter contamination 
and the potential for nosocomial infections. 
Still further, other concerns arise when taking blood samples from a 
patient. For example, excessive sampling may result in an excessive blood 
loss which may threaten a patient's safety and which may necessitate a 
transfusion. Also, inconsistent discard volumes may yield inaccurate lab 
values resulting in a possible misdiagnosis and mistreatment. 
In the past, when drawing sodium heparinized blood from a patient use has 
usually been made of two syringes for a blood draw from a central venous 
catheter. However, this requires not only the added costs of materials but 
also additional time on the part of the nurse or person drawing blood. 
As is known, blood sampling usually involves the collection of whole blood 
which contains all the blood elements. That is, whole blood is the sample 
of choice for blood gas analysis, determination of hemoglobin derivatives 
and the measurement of RBC constituents. In addition, most routine 
hematologic studies, such as complete blood count, erythrocyte 
sedimentation rate, reticulocyte and platelet counts as well as osmotic 
fregility tests require whole blood samples. 
Plasma is the liquid part of whole blood which contains all the blood 
proteins; serum is the liquid that remains after whole blood clots. Plasma 
and serum samples which contain most of the physiologically and clinically 
significant substances found in blood are used for most biochemical 
immunologic and coagulation studies. They also provide useful electrolyte 
evaluation, enzyme analysis, glucose concentration, protein determination 
and bilirubin level. 
Sample quantities required for diagnostic studies depend on the laboratory, 
available equipment and the type of test. The desired sample quantity 
determines the collection procedure and the type and size of container. 
For example, a single venipuncture with a conventional glass or disposable 
syringe can provide 15 millileters of blood. This is usually sufficient 
for many hematologic, immunologic, chemical and coagulation tests but 
hardly enough for a series of tests. 
In order to avoid multiple venipunctures when tests require a large blood 
sample, use has been made of an evacuated tube system, that is, a 
vacutainer with interchangeable glass tubes, optional draw capacities and 
a selection of additives. Evacuated tubes are commercially prepared with 
and without additives (usually indicated by a color-coated stopper) and 
with enough vacuum to draw a predetermined blood volumne, for example, 
from two to twenty milliliters per tube. The nature of the tests and 
patient's age and condition usually determine the appropriate blood 
sample, collection site and technique. Most tests require a venous sample. 
Although a relatively simple procedure, venipuncture must be performed 
carefully to avoid egmolysis or hemoconcentration of the sample to prevent 
hemotoma formation and to prevent damage to the patient's veins. 
In order to avoid discomfort from repeated infusion of drug products and 
blood collection stickings, central venus access devices have been 
utilized with critical care and longterm care patients. These devices may 
be simple or multiple lumen devices, Groshongs, PICC lines, implantable 
ports and arterial blood pressure lines. 
Currently, blood draws from the known vascular access devices are performed 
by two primary methods. 
In one case, use has been made of two plastic disposable syringes. One 
syringe is used to draw up discard which is mixed with saline or 
heparinized saline flush solution. The volume of this discard solution is 
usually five or ten millileters. However, this blood is not suitable for 
testing and would give false results. The second syringe is then used to 
draw up the pure blood sample for the prescribed test procedure. The 
volume of the pure blood sample is dependent on the test or tests needed 
to be performed but usually used in the range of from two to twenty 
milliliters. The pure blood is then transfered to the appropriate 
evacuated container or containers, i.e. a vacutainer, for the actual test 
and is then transported to the laboratory. 
The second method of blood draw collects the sample by using a standard 
blood collection syringe and needle affixed to the vascular access device 
while employing the appropriate evacuated container for the desired test 
procedure. This method is not recommended by many catheter manufacturers 
because of the potential for collapsing the catheter with the vacuum in 
the collection tube. In particular, the method is not usually recommended 
for PICC lines, Groshong catheters and Landmark catheters. 
The practice of home intravenous therapy has become increasingly popular 
with patients receiving intravenous antibiotics, chemotherapy, hydration 
fluids and total parenteral nutrition at home. Usually, the patients 
benefit in many ways from such therapy, the most obvious benefit being 
financial since costs are generally less than in institutional intravenous 
therapy. 
A variety of venous access devices have been developed for intravenous 
therapy and may include single, dual or triple lumens and may be external, 
peripheral or central or implanted. In many cases, a discard of blood is 
made followed by collection of a whole blood sample. Thereafter, flushing 
is usually performed with heparin or a saline solution. 
Accordingly, it is an object of the invention to reduce the risk of 
inadvertant blood spills or leakages when drawing blood from a patient. 
It is another object of the invention to utilize one syringe for obtaining 
a whole blood sample from a patient. 
It is another object of the invention to reduce the time and materials 
required for obtaining a whole blood sample from a patient. 
It is another object of the invention to collect a blood sample and 
maintain the sample in a contamination-free manner. 
It is another object of the invention to separately obtain a discard and a 
whole blood sample from a patient in a sequential manner without 
contamination of the blood sample. 
Briefly, the invention provides a dual chamber syringe for collecting blood 
samples. In addition, the invention provides a blood collecting system 
employing the dual chamber syringe with a storage device. 
More particularly, the dual chamber syringe is comprised of a one-piece 
cylindrical barrel having an open end and a tip defining a closed end with 
a duct extending therefrom. In addition, the syringe employs a first or 
foremost piston which is slidably mounted in the barrel to move from a 
first position abutting the closed end to a second position spaced 
therefrom to define a first chamber for receiving a whole blood sample. A 
second or rearmost piston is also slidably mounted in the barrel to move 
between a first position adjacent the first piston and a second position 
spaced therefrom to define a second chamber therebetween for receiving a 
discard. A plunger is also connected to the second piston to extend from 
the barrel. This plunger serves to effect movement of the second piston 
relative to the barrel. 
The syringe also has a passageway disposed between the foremost piston and 
the barrel to define a communicating path between the duct in the tip of 
the barrel and a point between the two pistons. Still further, a 
collapsible means connects the two pistons so as to move the foremost 
piston with the rearmost piston after a predetermined movement of the 
rearmost piston has caused a filling of the second chamber with a first 
flow of blood from a patient so as to allow filling of the first chamber 
of the barrel with a second flow of blood from the patient. 
Basically, the dual chamber syringe is of a construction as described in 
U.S. Pat. No. 4,715,854. 
In use, the dual chamber syringe may be connected to a venous access device 
through a needle asembly or directly so as to withdraw blood from a 
patient as the plunger is retracted relative to the barrel. In this 
respect, initial retraction of the plunger causes a first flow of blood 
along with fluids in the venous access device to flow about the first 
piston in the barrel into the chamber forming between the two pistons. 
Thereafter, upon continued retraction of the plunger and movement of the 
foremost piston via the collapsible means, blood is drawn into the 
foremost chamber then forming between the foremost piston and the closed 
end of the barrel. In this manner, a mixed whole blood sample, for 
example, including blood and other fluids from the access device, is 
collected in the rearmost or discard chamber while whole unadulterated 
blood is collected in the foremost chamber. The syringe can then be 
connected to a storage device so that the blood from the foremost chamber 
of the syringe can be discharged into the storage device upon movement of 
the plunger into the barrel. 
The dual chamber syringe is also provided with a stop means for preventing 
movement of the plunger into the barrel after dispensing of the blood 
collected in the foremost chamber. This stop means prevents the discard in 
the rearmost chamber from inadvertantly being mixed with the pure blood. 
In those cases where the user wishes to expel the discard fluid, the stop 
means may be deactivated thereby freeing the plunger so as to be moved 
further into the barrel thereby discharging the discard from the rearmost 
chamber via the duct at the end of the syringe. 
The stop means for preventing movement of the plunger completely into the 
barrel may be mounted on the barrel or on the plunger. In this respect, 
the stop means may be in the form of a catch mounted on the barrel for 
abutting the plunger in a given position thereof in order to prevent 
further movement of the plunger into the barrel. The catch may also be 
pivotally mounted on the barrel to pivot out of abutment with the plunger 
in order to permit movement of the plunger into the barrel to effect 
dispensing of the discard in the rearmost chamber. 
The blood collecting system employs the dual chamber syringe as described 
above with a suitable storage device, for example, the storage device may 
be in the form of a vacuum tube system, that is, a vacutainer.

Referring to FIG. 1, the dual chamber syringe 10 is constructed in a manner 
similar to that as described in U.S. Pat. No. 4,715,854 and is used for 
collecting blood samples. To this end, the syringe 10 includes a one-piece 
cylindrical barrel 11 having an open end 12 and a tip 13 defining a closed 
end with a duct 14 extending therefrom. The barrel 11 may be made of any 
conventional materials suitable for syringes and may be provided with a 
suitable scale or marking indicative of the volume. As indicated, the tip 
13 is of connical shape while the duct 14 is centrally located on the axis 
of the barrel 11. 
In addition, the syringe 10 includes a pair of pistons 15, 16, each of 
which is slidably mounted in the barrel 11. The foremost piston 15 is 
movable from a first position abutting the closed end of the barrel 11 to 
a second position spaced therefrom to define a first chamber therebetween 
(see FIG. 3). In addition, the foremost piston 15 has a plurality of 
protuberances 17, for example, in the form of beads at the forward end so 
as to provide a slight spacing or gap between the foremost piston 15 and 
the tip 13 of the barrel 11. The second or rearmost piston 16 is movable 
between a position as shown in FIG. 1 adjacent the foremost piston 15 and 
a second position spaced therefrom to define a second chamber as indicated 
in FIG. 2. 
The syringe 10 includes a plunger 18 which is connected to the rearmost 
piston 16 and which extends from the barrel 11. This plunger 18 is of 
conventional structure and is used to move the pistons 15, 16 relative to 
the barrel. As indicated, the plunger 18 has four ribs 19 defining a 
cruciform shape, a cross-piece 20 at an intermediate point and a 
finger-gripping plate 21 at the end. 
A passageway 22 is disposed between the foremost piston 15 and the barrel 
11 to define a communicating path between the duct 14 and a point between 
the pistons 15, 16 with the foremost piston in the first position thereof 
as indicated in FIG. 1. In addition, baffles (not shown) may be provided 
within the passageway in a manner as described in U.S. Pat. No. 4,715,854. 
A collapsible means in the form of a string 23 (see FIG. 2) is secured to 
and between the pistons 15, 16. This string 23 serves to connect the 
pistons 15, 16 while causing the foremost piston 15 to move with the 
rearmost piston 16 after a predetermined movement of the rearmost piston 
16 from the position indicated in FIG. 1 to the position indicated in FIG. 
2. During this time, a chamber 24 between the two pistons 15, 16 can be 
filled with a first flow of blood from a patient. 
As indicated in FIG. 3, continued movement of the plunger 18 out of the 
barrel 11 causes the two pistons 15, 16 to move rearwardly thereby drawing 
blood into a second chamber 25 between the foremost piston 15 and the 
closed end of the barrel 11. 
A stop means 26 is mounted on a finger-gripping end 27 of the barrel 11 for 
preventing movement of the plunger 18 into the barrel 11 after dispensing 
of blood collected in the foremost chamber 25 so as to prevent dispensing 
of the fluid in the rearmost chamber 24 as indicated in FIG. 4. 
The stop means 26 includes a pivotally mounted catch 28 which is able to 
pivot out of abutment with the plunger 18 to permit movement of the 
plunger 18 out of the barrel 11, for example, from the position shown in 
FIG. 1 to the position shown in FIG. 3. In this respect, the catch 28 is 
in the form of a tab which is pushed aside by the cross-piece 20 on the 
plunger 18 during an upward movement of the plunger 18 as viewed. However, 
the catch 28 snaps back into the position as indicated in FIG. 2 so as to 
abut the cross-piece 20 and thereby prevent a return movement of the 
plunger 18 into the barrel 11. The catch 28 may also be pivoted away from 
the plunger 18 as indicated in FIG. 5 under a manually applied force so as 
to permit the plunger 18 to move into the barrel 11 to effect dispensing 
of blood from the rearmost chamber 24. 
The entire catch 28 may be pivotally mounted on the end of the barrel 11 so 
as to pivot between a position in abutment with the cross-piece 20 of the 
plunger 18 and a position spaced from the plunger 18. Referring to FIG. 6, 
the forward portion of the safety catch 28 may be of narrowed shape to fit 
between the ribs 19 of the plunger 18. 
The safety catch 28 which is used may be attached to the finger grip 27 of 
the syringe 10 using adhesive, by being staked in place or by being molded 
with the syringe finger grip 27. In addition, the safety catch 28 may be 
provided with a breakaway tab (not shown) which can be manually broken off 
when a discard fluid is to be discharged from the syringe. 
Refering to FIG. 4, the syringe 10 is fitted with a needle assembly 29 for 
penetrating an injection port, e.g. a rubber septum or a Y-Site on an 
administration set. However, there are some cases, such as an opening in a 
central line at a luer connection, in which the syringe 10 can be directly 
inserted in the line so that a needle is not required. 
As shown, the needle assembly 29 includes a hub 30 for mounting onto the 
tip 13 of the syringe barrel 11 and a hollow needle 31 secured to and 
extending from the hub 30. The mounting of the hub 30 to the tip 13 of the 
barrel may be of any suitable type, for example a luer lock, a luer slip 
or a threaded connection (not shown) may be used to connect the hub 30 to 
the barrel tip 13. 
In use, the syringe 10 is employed with a storage device 32 for collecting 
a blood sample. Such a storage device 32 may be in the form of a vacuum 
tube, such as vacutainer, which is of known construction, for example, 
having an evacuvated glass tube 33 with a rubber stopper or septum 34 at 
the open end. 
In order to obtain a blood sample or other fluid sample, from a patient, 
the needle 31 of the needle assembly 29 mounted on the syringe barrel 11 
is passed in known fashion into a venous access device (not shown) 
implanted in a patient, Next, the plunger 18 is retracted relative to the 
barrel 11 thereby causing a first flow of whole blood as well as fluid in 
the access device to be drawn into the rearmost chamber 24 located between 
the pistons 15, 16 (see FIG. 2). During this time, the initial blood flow 
flows through the duct 14 and passageway 22 into the rearmost chamber 24. 
At the same time, the cross-piece 20 of the plunger 18 moves past the 
catch 28 of the stop means 26. Typically, about 5 cc of fluid would be 
drawn from the access device. Continued movement of the plunger 18 out of 
the barrel 11 causes the string 23 to pull the foremost piston 15 along 
with the plunger 18 and rearmost piston 16. This, in turn, causes a sample 
of whole blood to flow from the access device through the needle 31 and 
the duct 14 directly into the chamber 25 between the piston 15 and the 
closed end of the barrel 11. Since both pistons 15, 16 are in frictional 
contact with the barrel 11, the rearmost chamber which contains the first 
blood flow (i.e. the discard) is sealed off not only from the outside 
environment but also from the foremost chamber 25 which now contains a 
whole blood sample. 
In cases where the syringe 10 is not provided with a needle, the tip 13 of 
the syringe 10 can be directly connected to a luer connection in order to 
obtain a fluid sample from a patient. In such cases, in order to discharge 
the fluid sample into a vacutainer 32, a needle assembly 29 would be 
secured to the tip 13 of the syringe barrel 11 in order to effect 
discharge through the rubber septum 34 on the vacutainer 32. 
After an appropriate blood sample has been withdrawn from the patient, for 
example, as indicated in FIG. 3, the syringe 10 is removed from the 
patient and connected to the vacutainer 32 as indicated in FIG. 4. In this 
respect, the needle 38 pierces through the rubber septum 33 of the 
vacutainer 32 so that the whole blood sample in the foremost chamber 25 
can be dispensed into the vacutainer 32. 
Referring to FIG. 4, when the plunger 18 is pushed into the barrel 11 from 
the position shown in FIG. 3, the blood in the foremost chamber 25 is 
forced out of the duct 14 while the discard fluid in the rearmost chamber 
24 between the pistons 15, 16, being substantially incompressible, 
maintains the integrity of the chamber 24 so that the pistons 15, 16 move 
in unison. 
As the foremost piston 15 approaches the closed end of the barrel 11, the 
piston 15 begins to move across the passageway 22. However, before the 
point is reached where the foremost piston 15 would permit communication 
of the passageway 22 with the rearmost chamber 24 between the pistons 15, 
16, the safety catch 28 would abut the cross-piece 20 of the plunger 18 
thus preventing further movement of the plunger 18. The syringe 10 would 
then be removed from the vacutainer 29. Thus, while a small amount of 
blood might remain within the duct 14 and passageway 22, this would 
prevent any discard fluid from flowing into the vacutainer 29 from the 
discard chamber 24. 
The syringe 11 may then be provided with a cap or other sealing type of 
device (not shown) over the duct 14 to prevent dispensing of any further 
blood or discard. Where desired, the cap (not shown) can be removed so 
that the discard fluid can be dispensed from the syringe 10 into a 
suitable receptable (not shown), for example, for disposable purposes. 
The point at which the foremost piston 15 ceases to move towards the tip 13 
of the barrel 11 coincides with the position at which the catch 28 abuts 
the cross-piece 22 of the plunger 18. Thus, in those cases where the user 
wishes to expel the discard fluid, the safety catch 27 is pushed aside so 
that the plunger 18 can move further into the barrel 11. 
Referring to FIG. 7 and 8, wherein like reference characters indicate like 
parts as above, a stop means 35 may be mounted on the plunger 18 for 
abutting against the syringe barrel 11. For example, the stop means 35 may 
include a pair of tabs 36 which are integral with the ribs 19 of the 
plunger 18 and which normally project beyond the plane of the syringe 
barrel 11. In addition, the tabs 33 are sufficiently resilient so as to be 
depressed inwardly of the plane of the barrel 11 so as to slide within the 
interior of the barrel 11 as indicated in FIG. 7. When the plunger 18 is 
moved in a direction out of the barrel 11, the tabs 36 are able to spring 
outwardly so that a return motion of the plunger 18 into the barrel 11 can 
be prevented when the tabs 33 engage against the end of the barrel 11. 
Since the syringe 10 is capable of drawing two sequential samples from a 
venous access device, the time and material involved in drawing two 
samples from a patient can be reduced with respect to the previous use of 
two syringes for the same purpose. 
The invention thus provides a dual chamber syringe which requires opening 
of a venous access system only once in order to obtain a whole blood 
sample from a patient for testing purposes. Accordingly, there is less 
exposure to blood and the liklihood of fewer spills. 
Further, the dual chamber syringe allows a whole blood sample to remain 
contamination-free from the discard fluid which is initially drawn from 
the patient. In addition, the discard fluid will not mix with the whole 
blood sample when moving from the syringe to a vacutainer.