Abstract:
Novel devices which can be used to both collect blood samples from and administer medical fluids to a patient on a repeated and continual basis using one rather than multiple needle insertions. The devices are capable of removing blood from one of the patient&#39;s veins using the intrinsic venous pressure of the blood and capillary action of the device, thereby preventing vacuum-induced collapse of the vein. The device typically includes a main tubing segment confluently connected to a cannula for insertion in the patient&#39;s vein. A syringe port and a volumeter for collecting blood branch separately from the main tubing segment. The device is used to collect blood by attaching an empty blood collection syringe to the syringe port, inserting the cannula in the patient&#39;s vein, allowing passive flow of blood from the main tubing segment into the volumeter under intrinsic venous blood pressure and capillary action, and then facilitating active flow of blood from the volumeter into the blood collection syringe by extending the syringe plunger. The blood-filled syringe may be replaced by additional empty blood collection syringes and the procedure repeated, as needed, depending on the quantity of blood to be obtained. The device may be used to administer medical fluids to the patient by first removing the residual blood from the main tubing segment and volumeter, flushing the main tubing segment with sterile normal saline and administering the fluids to the patient through the main tubing segment from a medical fluid syringe or catheter attached to the syringe port.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to syringes and other devices for removing blood from and administering medical fluids to a patient. More particularly, the present invention relates to novel devices which can be used to both collect blood from a patient and administer medicines and other medical fluids to the patient using a single needle insertion.  
       BACKGROUND OF THE INVENTION  
       [0002]     Patients who undergo medical treatment in hospitals frequently require both extraction of blood for blood testing purposes and intravenous administration of medical fluids. Proper treatment of the patient may require that the blood be extracted and the medical fluids administered repeatedly and on a regular basis. In the past, this procedure has required that multiple needle insertions be made in various locations of the patient&#39;s body to access veins such as the external or internal jugular, subclavian, cephalic, femoral or saphenous veins. Multiple needle insertions not only result in considerable discomfort to the patient but also increase the risk of infection and compound the danger that medical personnel will be pricked by a contaminated needle.  
         [0003]     Conventional methods of drawing blood from a patient typically utilize partial vacuum pressure to draw the blood from one of the patient&#39;s veins into a collecting device. Such utilization of partial vacuum pressure to draw blood from the vein tends to prematurely collapse the vein, thus necessitating re-insertion of the collecting device in another vein or in the same vein at a separate location to draw additional blood. This problem is particularly common in the drawing of blood from infants and the aged, in which small, thin veins are typically the source for blood samples. Accordingly, a device is needed which facilitates both collection of blood from and administration of medical fluids to a patient on a repeated basis using one, rather than multiple, needle insertions and which prevents premature collapse of a vein by utilizing intrinsic venous blood pressure to collect blood.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention is generally directed to novel devices which can be used to both collect blood samples from and administer medical fluids to a patient on a repeated and continual basis using one rather than multiple needle insertions. The devices are capable of removing blood from one of the patient&#39;s veins using the intrinsic venous pressure of the blood and capillary action of the device, thereby preventing vacuum-induced collapse of the vein. The devices typically include a main tubing segment confluently connected to a cannula for insertion in the patient&#39;s vein. A syringe port and a device for estimating the rate of blood flow, hereinafter called a volumeter, branch separately from the main tubing segment. The device is used to collect blood by attaching an empty blood collection syringe to the syringe port, inserting the cannula in the patient&#39;s vein, allowing passive flow of blood from the main tubing segment into the volumeter under intrinsic venous blood pressure and capillary action, and then facilitating active flow of blood from the volumeter into the blood collection syringe by extending the syringe plunger. The blood-filled syringe may be replaced by additional empty blood collection syringes and the procedure repeated, as needed, depending on the quantity of blood to be collected. The device may be used to administer medical fluids to the patient by first drawing the residual blood from the main tubing segment and volumeter, flushing the main tubing segment with sterile normal saline and administering the fluids to the patient through the main tubing segment from a medical fluid syringe or catheter attached to the syringe port or to an auxiliary port connected to the main tubing segment.  
         [0005]     In one embodiment, a membrane permeable to air, but not to liquid, is attached distal to the volumeter, which may be a chamber, an elongated folded or coiled tubing, or any other element which is capable of enabling visual estimation of the rate of blood flow toward the membrane. The syringe port branches from the main tubing segment and accepts a syringe to collect blood for tests. The volumeter may be removed from the device, leaving the syringe port available for accepting a medication-filled syringe for administration of medical fluids to the patient.  
         [0006]     In another embodiment, a deformable reservoir is provided in fluid communication with the cannula and volumeter. The reservoir may be protected in the barrel of a syringe or other protective covering with vented openings along its barrel. After the blood-drawing procedure is completed using the blood collection syringe, residual blood may be effectively removed from the device by flushing the tubing with sterile normal saline. Removal of the reservoir unit from the device allows the remaining part of the device to be used as an ordinary “Y” tubing.  
         [0007]     In another embodiment, a main tubing segment confluently connected to a cannula for insertion in the patient&#39;s vein. A syringe port and a device for estimating the rate of blood flow, hereinafter called a volumeter, branch separately from the main tubing segment. The device is used to collect blood by attaching an empty blood collection syringe to the syringe port, inserting the cannula in the patient&#39;s vein, allowing passive flow of blood from the main tubing segment into the volumeter under intrinsic venous blood pressure and capillary action, and then facilitating active flow of blood from the volumeter into the blood collection syringe by extending the syringe plunger. The blood-filled syringe may be replaced by additional empty blood collection syringes and the procedure repeated, as needed, depending on the quantity of blood to be collected. The device may be used to administer medical fluids to the patient by first drawing the residual blood from the main tubing segment and volumeter, flushing the main tubing segment with sterile normal saline and administering the fluids to the patient through the main tubing segment from a medical fluid syringe or catheter attached to the syringe port or to an auxiliary port connected to the main tubing segment. Additional embodiments are disclosed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0009]      FIG. 1  is a perspective view of an illustrative embodiment of the device of the present invention, with a cannula of the device inserted in a patient (in phantom);  
         [0010]      FIG. 2  is a perspective view of another illustrative embodiment of the device of the present invention;  
         [0011]      FIG. 2A  is a side view of a folded tubing volumeter of the device of the present invention;  
         [0012]      FIG. 3  is a cross-sectional view taken along section lines  3 - 3  in  FIG. 2 ;  
         [0013]      FIG. 4  is an exploded, perspective view of still another illustrative embodiment of the device of the present invention;  
         [0014]      FIG. 5  is a side view of a port element of the device of  FIG. 4  and a cap device removably engaging the port;  
         [0015]      FIG. 6  is an exploded, perspective view of still another illustrative embodiment of the device of the present invention;  
         [0016]      FIG. 6A  is a side view of a port element of the device of  FIG. 6  and a blood receptacle removably engaging the port; and  
         [0017]      FIG. 6B  is a cross-section of a blood receptacle contained in a receptacle casing in another embodiment of the device of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     Referring initially to  FIG. 1  of the drawings, an illustrative embodiment of the device for collecting blood and administering medical fluids, hereinafter “device”, of the present invention is generally indicated by reference numeral  1 . The device  1  includes a main tubing segment  2  which is typically a flexible material. A hub  4  of a cannula  3  is threadibly or otherwise attached to the main tubing segment  2 . A tubing bifurcation  5  is provided in the end of the main tubing segment  2  which is opposite or distal to the cannula  3 , and the tubing bifurcation S may be continuous with or a separate element with respect to the main tubing segment  2 . A tubing clamp  6  is provided on the main tubing segment  2  between the cannula hub  4  and the tubing bifurcation  5 . The tubing clamp  6  may be any type of clamp which is capable of facilitating selective and reversible blocking of the flow of fluids through the main tubing segment  2 . The tubing clamp  6  is preferably capable of one-handed operation.  
         [0019]     A syringe tubing segment  9  extends from a syringe tubing leg  5   a  of the tubing bifurcation  5  and may be continuous with or a separate element with respect to the tubing bifurcation  5 . A syringe port  10  is provided in the end of the syringe tubing  9  which is opposite the tubing bifurcation  5 . The syringe port  10  may a needle-less syringe port such as a female luer-lock connector element or other type of threaded element known by those skilled in the art, or may be any type of threadless connector which is capable of providing reversible and secure fluid communication between a syringe  13  and the syringe tubing segment  9 . The syringe  13  may be conventional and typically includes a cylindrical syringe barrel  14  having a syringe connector  15  such as a male luer-lock connector element, for example, or other structure which is capable of removably and securely engaging the companion syringe port  10 . The syringe  13  typically further includes barrel flanges  16  and an extendible and retractable syringe plunger  17 .  
         [0020]     A collector tubing segment  19  extends from a collector tubing leg  5   b  of the tubing bifurcation  5  and may be continuous with or a separate element with respect to the tubing bifurcation  5 . An indicator unit  18  of the device  1  includes a volumeter tubing segment  20  which is provided in fluid communication with the collector tubing segment  19 . The indicator unit  18  may be removably attached to the collector tubing segment  19  by a tubing connector  21 , which may include a receiver element  22  provided on the collector tubing  19  and an insertion element  23  provided on the volumeter tubing segment  20 , as shown. Alternatively, the receiver element  22  may be provided on the volumeter tubing segment  20  and the insertion element  23  may be provided on the collector tubing segment  19 . When provided on the collector tubing segment  19 , the receiver element  22  may be a syringe port adapted for removably receiving a syringe for the administration of medical fluids to a patient, as hereinafter further described. It is understood that the indicator unit  18  may be fixedly rather than removably attached to the collector tubing segment  19 . Further in the alternative, a connector  7  (in phantom) may be provided between the clamp  6  and the bifurcation  5  to facilitate disconnecting the syringe tubing segment  9  and syringe port  10 , together with the connected indicator unit  18 , from the main tubing segment  2 , in order to discard the syringe tubing segment  9  and indicator unit  18 , as desired.  
         [0021]     The indicator unit  18  may further include a volumeter  26 , which is typically a volumeter chamber and made of a transparent material, provided in the volumeter tubing segment  20 . Alternatively, the volumeter  26  may be an elongated segment of transparent coiled or folded tubing, as hereinafter described with respect to  FIGS. 2, 2A  and  4 . Membrane tubing  28  of the indicator unit  18  extends from the volumeter  26 , and an air-permeable membrane  29  is provided on the membrane tubing  28 . The air-permeable membrane  29  is preferably impermeable to liquids and may be any structure which is capable of facilitating bidirectional flow of air in the membrane tubing  28  toward the membrane  29  or bidirectional flow of air between the volumeter chamber  26  and the membrane tubing  28  while preventing the flow of blood out from the membrane tubing  28 .  
         [0022]     Referring again to  FIG. 1 , in typical use, the device  1  is initially used to remove blood from a subcutaneous vein of a patient  30  for blood sampling purposes. Accordingly, the clamp  6  is adjusted to the closed position to seal the main tubing segment  2  between the cannula  3  and the tubing bifurcation  5 . The tubing connector  21  is inspected to ensure an airtight and fluid-tight connection between the collector tubing segment  19  and the volumeter tubing segment  20  of the indicator unit  18 . With the main tubing segment  2 , the syringe tubing segment  9 , the collector tubing segment  19  and the indicator unit  18  containing air, the cannula  3  is inserted into the vein of the patient  30  through the skin, as shown. The cannula  3  is typically taped in place to immobilize the device  1  on the patient  30 .  
         [0023]     After the syringe connector  15  of the syringe  13  is attached to the syringe port  10  of the syringe tubing segment  9 , the clamp  6  is adjusted to open the main tubing segment  2 . Accordingly, as blood flows from the vein of the patient  30  through the cannula  3  and the main tubing segment  2 , air is displaced by the advancing blood from the main tubing segment  2 , the collector tubing segment  19  and the indicator unit  18 , respectively, toward the membrane  29 . Due to the resulting air pressure in the collector tubing segment  19  being low relative to the higher venous pressure in the main tubing segment  2 , the blood flows from the main tubing segment  2  and collector tubing leg  5   b  of the tubing bifurcation  5 , into the collector tubing segment  19  and does not enter the syringe tubing segment  9 . Blood continues to flow from the main tubing segment  2  and collector tubing segment  19 , through the tubing connector  21  and volumeter tubing segment  20 , respectively, of the indicator unit  18  and enters and collects in the volumeter chamber  26 . Next, the syringe plunger  17  is slowly extended from the syringe barrel  14  of the blood collecting syringe  13  to initially draw air from the syringe tubing segment  9  and into the syringe barrel  14  of the syringe  13 , thereby inducing a drop in air pressure inside the syringe tubing segment  9  relative to both the pressure in the collector tubing segment  19  and the intrinsic venous pressure in the main tubing segment  2 . This pressure drop causes blood to flow from the volumeter chamber  26 , the volumeter tubing segment  20  and the collector tubing segment  19 , respectively, and enter the syringe tubing segment  9  and then the syringe barrel  14  of the syringe  13 .  
         [0024]     As the syringe plunger  17  is slowly pulled from the syringe barrel  14 , care is taken to avoid pulling the syringe plunger  17  at a rate which causes the blood supply in the volumeter chamber  26  to be depleted and the air/blood interface to advance through the collector tubing segment  19  and beyond the tubing bifurcation  5 , in which case air would be drawn from the collector tubing segment  19  and into the syringe tubing segment  9 , and thus into the collecting syringe  13 . This extension of the plunger  17  from the syringe barrel  14  at a relatively slow, controlled rate ensures that blood is extracted from the vein of the patient  30  and into the device  1  using the intrinsic flow pressure of the blood in the vein and prevents application of vacuum pressure to the vein which would tend to collapse the vein and hinder further flow of blood therefrom, as well as prevents or minimizes hemolysis of red blood cells in the extracted blood. Typically, the syringe plunger  17  is pulled from the syringe barrel  14  at a rate which is sufficient to facilitate maintaining a substantially constant volume of blood in the volumeter chamber  26  as blood continues to be obtained from the main tubing segment  2 , through the syringe tubing segment  9  and into the blood collection syringe  13 . This is ensured by keeping the air/fluid interface distal to the bifurcation  5  and proximal to the membrane  29 , facilitated by a visual assessment of the blood flow rate provided by the volumeter chamber  26 . It is understood that the volumeter  26  may be omitted from the indicator unit  18 , in which case the indicator unit  18  may be a segment of clear tubing or any other element which is capable of enabling a user of the device  1  to visually inspect the progress of blood flow therethrough and prevent the air/fluid interface from passing beyond the bifurcation  5  to the syringe tubing segment  9  while obtaining the blood sample.  
         [0025]     After the desired volume of blood has been collected in the syringe barrel  14 , the tubing clamp  6  is adjusted to block further flow of blood through the main tubing segment  2 . With the tubing clamp  6  remaining in the closed position, the syringe plunger  17  of the syringe 13  is extended from the syringe barrel  14  until all residual blood has been drawn from the indicator unit  18 , the collector tubing segment  19  and the syringe tubing segment  9 , and into the syringe barrel  14 . Simultaneously, air is drawn through the indicator unit  18  through the membrane  29 , the collector tubing segment  19  and the syringe tubing segment  9 , respectively, until these elements are filled with air. The blood-filled syringe  13  is then removed from the device  1  by disconnecting the syringe connector  15  from the syringe port  10 , and the blood collected in the syringe  13  is subjected to blood testing. Additional blood samples may be collected in an additional syringe or syringes, as needed, by attaching each additional empty syringe  13  to the syringe tubing segment  9  at the syringe port  10  and collecting the additional samples of blood in the syringe  13  or successive syringes  13 , in the manner heretofore described.  
         [0026]     After the blood sample or samples is/are collected, the device  1  may be used to administer medical fluids to the patient  30 , as follows. A syringe  13 , the barrel  14  of which contains a supply of saline flush solution, is initially attached to the syringe port  10 . As the syringe plunger  17  is subsequently depressed into the fluid-filled syringe barrel  14 , the saline solution is ejected therefrom and flows through the syringe tubing segment  9 , the collector tubing segment  19 , the volumeter tubing segment  20  and into the volumeter chamber  26 , respectively. The volumeter tubing segment  20  may then be disconnected from the collector tubing segment  19  at the tubing connector  21  and discarded along with the volumeter chamber  26 , the membrane tubing  28  and the membrane  29  of the indicator unit  18 , as desired. The tubing clamp  6  is then again adjusted to the open position and depression of the syringe plunger  17  into the syringe barrel  14  is continued to flush the main tubing segment  2  with saline flush solution. The syringe  13  is then removed and a replacement syringe  13  containing a fluid medication or a catheter (not shown) connected to an IV bag (not shown) may then be attached to the syringe port  10  for the administration of medical fluids to the patient  30  through the syringe tubing segment  9 , or alternatively, through the syringe port  22 , the collector tubing segment  19  and the main tubing segment  2 , respectively.  
         [0027]     In the event that additional blood samples from the patient  30  are required after administration of the medical fluids from the syringe  13  has begun or been completed, and fluid contents of the syringe  13  are expelled into the syringe tubing segment  9 , the tubing clamp  6  is adjusted to the closed position. A replacement indicator unit  18  may then be attached to the collector tubing segment  19  at the tubing connector  21 . The plunger  17  of syringe  13 , emptied of the medical fluid contents, is then extended to draw residual medical fluids from the indicator unit  18  and syringe tubing segment  9 , and the syringe  13  is removed from the syringe port  10  and discarded. The clamp  6  is now opened, allowing fluid from main tubing segment  2  to flow toward membrane  29 . Plunger  17  is further extended recovering any saline/blood mix. The clamp  6  is then closed, and another empty blood-collecting syringe  13  is connected to the syringe port  10 , the tubing clamp  6  is again adjusted to the open position, and the syringe  13  is used to obtain the additional blood from the patient  30 , respectively, as heretofore described.  
         [0028]     Referring next to  FIGS. 2, 2A  and  3  of the drawings, another illustrative embodiment of the device of the present invention is generally indicated by reference numeral  31  and includes a main tubing segment  32 , to one end of which is securely connected a hub  34  of a cannula  33 . A tubing bifurcation  35  is provided in the opposite end of the main tubing segment  32  and defines a syringe tubing leg  35   a  and an adjacent collector tubing leg  35   b.  A tubing clamp  36  of selected design is provided on the main tubing segment  32 , between the cannula hub  34  and the tubing bifurcation  35 . Preferably, the tubing clamp  36  is capable of one-handed operation.  
         [0029]     A syringe tubing segment  39  extends from the syringe tubing leg  35   a  of the tubing bifurcation  35 . A syringe port  40 , which is typically a needle-less luer-lock connector, for example, is provided in the end of the syringe tubing  39  which is distal to the tubing bifurcation  35 . A syringe  43 , typically including a cylindrical syringe barrel  44  having a syringe connector  45  such as a male luer-lock connector element, for example, removably engages the syringe port  40  in fluid-tight connection therewith. The blood collection syringe  43  may be conventional and typically further includes barrel flanges  46  and an extendible and retractable syringe plunger  47 .  
         [0030]     A collector tubing segment  49  extends from the collector tubing leg  35   b  of the tubing bifurcation  35 . A indicator unit  48  may be removably connected to the collector tubing segment  49  at a tubing connector  51 , and a protective container such as a covering syringe  63  may be removably connected to the indicator unit  48  for purposes which will be hereinafter described. The indicator unit  48  may include a volumeter  56  which is typically provided between a port tubing segment  59  and a volumeter tubing segment  50  and may be encased in a transparent volumeter casing  57 . The tubing connector  51  may include a receiver element  52  which is typically provided on the collector tubing segment  49  and removably receives an insertion element  53  typically provided on the volumeter tubing segment  50 . Alternatively, the receiver element  52  may be provided on the volumeter tubing segment  50  and the insertion element  53  provided on the collector tubing segment  49 . The volumeter  56  is typically a clear, transparent device having an elongated, generally spiral configuration, as shown in  FIG. 2 . However, it is understood that the volumeter  56  may alternatively be a volumeter chamber such as the volumeter chamber  26  heretofore described with respect to  FIG. 1 . Still further in the alternative, as shown in  FIG. 2A , the volumeter  61  may be configured as a folded volumeter tubing that is folded into a zigzag pattern in a transparent volumeter casing  62 .  
         [0031]     A syringe port  60 , which may be a needle-less female luer-lock connector, for example, is provided on the port tubing segment  59  of the indicator unit  48 . As shown in  FIG. 3 , a residual blood collection reservoir  69  typically may be covered by a syringe barrel  64  of a protective container such as the covering syringe  63  having a syringe connector  65  which may be a male luer-lock connector element, for example, for removable connection to the companion syringe port  60 . The protective covering syringe  63  may include a pair of barrel flanges  66  extending from the syringe barrel  64  and a syringe plunger  67  slidably disposed in the barrel interior  68  ( FIG. 3 ) of the syringe barrel  64 .  
         [0032]     As shown in  FIGS. 2 and 3 , one or more barrel openings  64   a  extend through the wall of the syringe barrel  64 . As shown in  FIG. 3 , the blood-collecting reservoir  69  is provided in the barrel interior  68  of the syringe barrel  64 . The reservoir  69  may be a very thin, easily deformable balloon-type structure, which is typically partially collapsed and is provided in fluid communication with the cannula  33  and volumeter  56 . The reservoir  69  is formed typically of a thin plastic material such as SARAN WRAP (trademark) or a rubber material or other easily deformable material that allows the interior volume of the reservoir  69  to be maintained at ambient air pressure. The reservoir  69  includes an intake end  69   a  which is typically secured in the syringe connector  65  and has an intake opening (not shown) which faces the syringe port  60 . The distal end of the reservoir  69  is affixed to the plunger  67 , as shown in  FIG. 3 . In operation of the device  31  as hereinafter described, the reservoir  69  is designed to receive residual blood from the volumeter  56 . By withdrawal of the syringe plunger  47  slowly from the syringe barrel  44  of the syringe  43 , blood is drawn from the reservoir  69 ; through the volumeter  56 , the collector tubing segment  49  and the syringe tubing segment  39 , respectively; and into the syringe barrel  44  of the syringe  43 . The indicator unit  48  can then be removed from the collector tubing segment  49  at the tubing connector  51  and discarded.  
         [0033]     In typical use the device  31  is initially used to obtain blood from a subcutaneous vein of a patient (not shown) and may thereafter be used to administer medical fluids to the patient, as heretofore described with respect to the device  1  of  FIG. 1 . Accordingly, the clamp  36  is adjusted to the closed position to seal the main tubing segment  32  between the cannula  33  and the tubing bifurcation  35 ; the cannula  33  is inserted into the vein of the patient; the syringe connector  45  of the blood collection syringe  43  is attached to the syringe port  40  of the syringe tubing segment  39 ; and the clamp  36  is adjusted to open the main tubing segment  32 . As blood flows from the vein of the patient through the cannula  33  and into the main tubing segment  32 , air is displaced by the advancing blood from the main tubing segment  32 , the collector tubing segment  49 , the indicator unit  48 , and into the partially-collapsed blood collection reservoir  69  ( FIG. 3 ). Due to the resulting air pressure in the collector tubing segment  49  being low relative to the higher venous pressure in the main syringe tubing  32  and therefore, facilitated by the expandible blood collection reservoir  69 , the blood flows from the main tubing segment  32  and collector tubing leg  35   b  of the tubing bifurcation  35 , into the collector tubing segment  49  and does not enter the syringe tubing segment  39 . Blood continues to flow from the main tubing segment  32  and collector tubing segment  49 , through the tubing connector  51  and volumeter tubing segment  50 , respectively, and enters and collects in the volumeter  56 . In the event that some of the blood flows from the volumeter  56  and through the port tubing segment  59  and the syringe port  60  and into the syringe connector  65  of the covering syringe  63 , this blood is collected-in the blood collecting reservoir  69  ( FIG. 3 ) and may later be expelled from the covering syringe  63  as an additional blood sample, as hereinafter further described.  
         [0034]     After the blood has entered the volumeter  56  from the collector tubing segment  49 , as heretofore described, the syringe plunger  47  of the blood collection syringe  43  is slowly extended from the syringe barrel  44  of the blood collecting syringe  43  to initially draw air from the syringe tubing segment  39  and into the syringe barrel  44  of the syringe  43 , thereby inducing a drop in air pressure inside the syringe tubing segment  39  relative to the air pressure in the collector tubing segment  49 . This causes blood to flow from the volumeter  56 , the volumeter tubing segment  50  and the collector tubing segment  49 , respectively, and enter the syringe tubing segment  39  and the syringe barrel  44  of the syringe  43 .  
         [0035]     As the syringe plunger  47  is slowly pulled from the syringe barrel  44  of the blood collection syringe  43 , care is taken to avoid pulling the syringe plunger  47  at a rate which causes the blood supply in the volumeter  56  to be depleted and the air/blood interface to advance beyond the tubing bifurcation  35 , in which case air would be drawn from the collector tubing segment  49  and into the syringe tubing segment  39 . Typically, the syringe plunger  47  is pulled from the syringe barrel  44  at a rate which is sufficient to facilitate maintaining a substantially constant volume of blood in the volumeter  56  as blood continues to be obtained from the main tubing segment  32 , through the collector tubing segment  49  and volumeter tubing segment  50 , respectively, and into the volumeter  56 . This extension of the plunger  47  from the syringe barrel  44  at a relatively slow, controlled rate ensures that blood is extracted from the vein of the patient and into the device  31  using the intrinsic flow pressure of the blood in the vein.  
         [0036]     After the desired volume of blood has been collected in the syringe barrel  44  of the blood collection syringe  43 , the tubing clamp  36  is adjusted to block further flow of blood through the main tubing segment  32 . While the tubing clamp  36  remains in the closed position, the syringe plunger  47  of the blood collection syringe  43  is extended from the syringe barrel  44  until all residual blood has been drawn from the volumeter  56 , the volumeter tubing segment  50 , the collector tubing segment  49  and the syringe tubing segment  39 , and into the syringe barrel  44 . The blood-filled blood collection syringe  43  is then removed from the device  31  by disconnecting the syringe connector  45  from the syringe port  40 , and the blood collected therein is subjected to blood testing. Additional blood samples may be collected in an additional blood collection syringe or syringes, as needed, by attaching each additional empty blood collection syringe  43  to the syringe tubing segment  39  at the syringe port  40  and collecting the additional samples of blood in the blood collection syringe  43  or successive blood collection syringes  43 , as heretofore described. Any blood collected in the blood collection reservoir  69  ( FIG. 3 ) may be collected in the barrel  44  of the blood collection syringe  43  by pulling the plunger  47  from the syringe barrel  44 .  
         [0037]     The device  31  may be used to administer medical fluids to the patient, as heretofore described with respect to the device  1  of  FIG. 1  and as follows. After removal of the blood-filled blood collecting syringe  43  from the syringe port  40 , a replacement syringe  43 , the barrel  44  of which contains a supply of sterile normal saline flush solution, is securely attached to the syringe port  40 . The syringe plunger  47  is then depressed into the syringe barrel  44  to force the saline solution through the syringe tubing segment  39 ; the collector tubing segment  49 ; the volumeter tubing segment  50 , the volumeter  56  and the port tubing segment  59  of the indicator unit  48 ; and into the blood collection reservoir  69  ( FIG. 3 ), respectively. The indicator unit  48  may then be disconnected from the collector tubing segment  49  at the tubing connector  51  and discarded along with the residual blood collection reservoir  69  encased in the covering syringe  63 . Alternatively, any blood/saline mix remaining in the reservoir  69  may be used for blood culture by allowing partial vacuum test tube or bottle to pull specimen into appropriate container. The tubing clamp  36  is then again adjusted to the open position and depression of the syringe plunger  47  into the syringe barrel  44  is continued to flush the main tubing segment  32  with saline flush solution. The syringe  43  is then removed and a replacement syringe  43  containing a fluid medication or a catheter (not shown) connected to an IV bag (not shown) may then be attached to the syringe port  40  for the administration of medical fluids to the patient through the syringe tubing segment  39  and the main tubing segment  32 , respectively. Additional blood samples may be obtained from the patient by removing the medical fluid-filled syringe  43  from the syringe port  40 , connecting a replacement indicator unit  48  and residual blood collection reservoir  69  to the collector tubing segment  49 , and connecting an empty blood-collecting syringe  43  to the syringe port  40  to obtain the blood from the patient, in the manner heretofore described.  
         [0038]     Referring next to  FIG. 4  of the drawings, still another illustrative embodiment of the device of the present invention is generally indicated by reference numeral  71  and includes a main tubing segment  72  to which a hub  74  of a cannula  73  is threadibly or otherwise attached. A tubing bifurcation  75  is provided in the end of the main tubing segment  72 , and a tubing clamp  76  is provided on the main tubing segment  72 . The tubing clamp  76  is preferably capable of one-handed operation.  
         [0039]     A syringe tubing segment  79  extends from a syringe tubing leg  75   a  of the tubing bifurcation  75 , and a syringe port  80  is provided in the end of the syringe tubing  79 . A syringe  83  which may be conventional typically includes a cylindrical syringe barrel  84  having a syringe connector  85  such as a male luer-lock connector element, for example, or other structure which removably engages the syringe port  80 . The syringe  83  typically further includes barrel flanges  86  and an extendible and retractable syringe plunger  87 .  
         [0040]     A collector tubing segment  89  extends from a collector tubing leg  75   b  of the tubing bifurcation  75 . A syringe port  91 , which may be a female luer-lock connector element, for example, is provided on the collector tubing segment  89 . An indicator unit  88  includes a volumeter tubing segment  90  having a connector element (not shown) such as a male luer-lock connector which is removably connected to the syringe port  91 . The indicator unit  88  typically further includes a blood volumeter  96  which may be a transparent coiled or folded tubing as shown and heretofore described with respect to the volumeter  56  of the device  31  of  FIG. 2 . Alternatively, the blood volumeter  96  may be a volumeter chamber such as the volumeter chamber  26  heretofore described with respect to  FIG. 1 . A membrane tubing segment  98  of the indicator unit  88  extends from the volumeter  96 , and an self-sealing or other port  99  having a port receptacle  99   a  is provided on the tubing segment  98 . Additionally, a cap device  100 , preferably comprised of a distal air permeable membrane  102  and a proximal needle-less blunt probe or a protected needle  101 , is capable of being attached securely to the port  99 . It will be appreciated from a consideration of  FIG. 5  that attachment of the cap device  100  to the port  99  causes the needle protected or needle-less probe  101  to be inserted into the receptacle  99   a  of the self-sealing port  99 , and toward the membrane tubing segment  98 . This will ensure that ambient outside pressure is allowed through the membrane  102  and into the membrane tubing segment  98 . Since the intrinsic vein pressure is higher than ambient air pressure, blood will then flow toward the cap device  100 . The air-permeable membrane  102  is preferably impermeable to liquids and may be any structure which is capable of facilitating flow of air from the volumeter  96  and the membrane tubing  98  while preventing the flow of blood from the membrane tubing  98 . The exterior surface of the cap device  100  may be provided with cap threads (not shown) which engage interior cap threads (not shown) of the port  99  to secure the membrane cap device  100  on the port  99 . Alternatively, the cap device  100  may be securely attached to the port  99  using any other suitable technique known by those skilled in the art.  
         [0041]     In use, the device  71  may be used to obtain blood samples from a patient into one or multiple blood collection syringes  83  successively connected to the syringe port  80 . After all blood samples have been obtained at the port  80 , the tubing is then flushed with sterile normal saline solution in the same manner as heretofore described with respect to the syringe  13  of the device  1  of  FIG. 1  and the syringe  43  of the device  31  of  FIG. 2 . Medical fluids may then be introduced into the patient using a fluid-filled syringe or successive fluid-filled syringes  83  in the same manner as heretofore described with respect to the device  1  of  FIG. 1  and the device  31  of  FIG. 2 . In addition, the indicator unit  88  of the device  71  may be removed from the syringe port  91  of the device  71  and a syringe (not shown) or IV catheter (not shown) may be connected to the syringe port  91  for the introduction of medical fluids into the patient along with the medical fluids introduced into the device  71  through the syringe tubing segment  79  using the syringe  83  or successive syringes  83  filled with medical fluid.  
         [0042]     Referring next to  FIGS. 6-6B , another illustrative embodiment of the device of the present invention is generally indicated by reference numeral  111  and includes a main tubing segment  112  to which is attached a hub  114  of a cannula  113 . A collector tubing segment  129  extends from the main tubing segment  112 . A tubing clamp  116 , which is preferably capable of one-handed operation, is provided in the main tubing segment  112 . A collection unit  128  includes a volumeter tubing segment  140  which is provided in fluid communication with the collector tubing segment  129 . The collection unit  128  may be removably attached to the collector tubing segment  129  by a tubing connector  131  of selected design.  
         [0043]     The collection unit  128  typically further includes a volumeter  136  that may be contained inside a volumeter casing  137 . A port tubing segment  139  extends from the volumeter  136 , and a port  141  is provided on the distal end of the port tubing segment  139 . The port  141  may be a needle-less port or a protective needle port, for example, known by those skilled in the art. As shown in  FIG. 6A , a port opening  143  extends into the port  141  for removably receiving a companion receptacle connector  149  that extends from an inlet end of a collapsible and expandable blood receptacle  146 . The blood receptacle  146  may be made of thin plastic, rubber or other deformable material and has a volume of typically from about ½ cc to about 10 cc, depending on laboratory requirements and the type of blood test to be conducted. As further shown in  FIG. 6A , the blood receptacle  146  may be attached to an attachment sleeve  147  into which the receptacle connector  149  extends. As shown in  FIG. 6 , the port  141  may be provided with exterior port threads  142  that engage interior sleeve threads  148  provided in the attachment sleeve  147  to removably attach the blood receptacle  146  in fluid communication with the port  141 . However, it is understood that the attachment sleeve  147  may be attached to the port  141  using any of a variety of alternative techniques known by those skilled in the art. For larger-sized blood receptacles  146  in which the quantity of blood to be collected therein is greater than typically about 1 cc, the blood receptacle  146  may be provided inside a receptacle casing  150  having one or more casing openings  151 . The distal end of the blood receptacle  146  is attached or tethered to the receptacle casing  150  using an enclosure anchor  152 .  
         [0044]     As further shown in  FIG. 6 , a tubing bifurcation  115  may be provided in the distal end of the main tubing segment  112 , in which case a syringe tubing segment  119  extends from a syringe tubing leg  115   a  of the tubing bifurcation  115  and the collector tubing segment  129  extends from a collector tubing leg  115   b  of the tubing bifurcation  115 . A syringe port  120  is provided in the distal end of the syringe tubing  119  and removably receives a syringe  123  to obtain blood samples from and/or administer medical fluids to a patient, as hereinafter described. Additionally, the blood receptacle  146  is be used to collect blood samples from a patient for subsequent testing of the blood samples and then removed from the port  141  for testing of the blood samples. A syringe (not shown) or catheter can then be attached to the port  141  for the administration of medical fluids to the patient, as hereinafter further described.  
         [0045]     In typical use, the cannula  113  is inserted into a subcutaneous vein (not shown) of a patient and the device  111  is taped in place. Because venous blood pressure inside the accessed vein is higher than ambient air pressure applied to the exterior of the blood receptacle  146 , blood flows from the vein though the main tubing segment  112 , the collector tubing segment  129  and the volumeter  136 , respectively, and enters the blood receptacle  146 . After the blood receptacle  146  is filled to capacity with blood, the attachment sleeve  147  is removed from the port  141  and additional empty blood receptacles  146  can be successively attached to the port  141  to obtain additional blood samples, as needed, which blood receptacles  146  may be sized according to the blood tests desired. After all blood specimens are collected, last blood receptacle  146  is removed from the port  141  and discarded, thereby exposing the self-sealing port  141 . Normal saline is then used to flush the device  111  typically through the port  141 , and an IV line (not shown) may be connected to the port  141 , after which the device  111  is used as ordinary extension tubing. Alternatively, the device  111  can be flushed with sterile normal saline and the medical fluids can be administered to the patient using a syringe  123  or IV line connected to the syringe port  120 , as heretofore described with respect to the embodiments of  FIGS. 1-4 .  
         [0046]     During blood sampling, in the event that the cannula  113  is inserted in a large vein, blood typically flows rapidly into the blood receptacle  146 , and therefore, the syringe  123  is not needed to obtain the blood samples. On the other hand, in the event that the cannula  113  is inserted in a small vein, blood typically flows slowly into the blood receptacle  146 , and thus, the syringe  123  can be used instead to obtain the blood samples through the syringe port  120 . A replacement syringe  123  or IV line (not shown) can then be attached to the port  120  for the administration of medical fluids to the patient through the syringe tubing segment  119 . Accordingly, the syringe tubing segment  119 , bifurcation  115 , and syringe port  120  are optional components and can optionally be omitted from the device  111 , as desired, since the port  141  is suitable for both obtaining blood samples from and administering medical fluids to the patient. Furthermore, the volumeter  136  is an optional element designed to assist the user in estimating the quantity of blood flowing from the main tubing segment  112  and into the receptacle  146 , in use of the device  111 .  
         [0047]     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.