GB1590101A - Infusion tube access site - Google Patents

Description

(54) IMPROVED INFUSION TUBE ACCESS SITE (71) We, CORDIS DOW CORP., a corporation organised and existing under the laws of the State of Delaware, United States of America, of 999 Brickell Avenue, Miami, State of Florida 33145, United States of America, (assignee of SAMUEL BURD), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an improved construction of the site on a tube external of the patient to enable leak-free withdrawal of fluid samples from, or the injection of medicants into, a fluid flowing in the tube. The invention is particularly useful in blood tube sets used for the passage of blood between the patient and an artificial kidney or a blood oxygenator.

Commercial blood-passage tubing sets have typically provided one or more injection sites at which blood samples may be taken from, or chemicals injected into, the blood by hypodermic needle piercing the tube wall. Smooth, nontoxic tubing must be used for the blood passage for patient safety; such tubing has relatively thin walls, little elasticity and is typically non-sealing after being pierced. In order to prevent leakage into or from blood tubing pierced with a hypodermic needle, elastomeric materials having some ability to self-seal have been used in the past. The elastomeric material is so arranged with the blood tube that the needle puncture is made through the self-sealing elastomeric material before piercing the tube. However, the self-sealing characteristics of the best commercially available material, natural rubber latex, are insufficient at times to prevent leakage into the blood tube under some of the conditions of use which are periodically encountered. For example, the difficulty of self-sealing increases as the needle size increases, as the time of needle penetration increases, and as the number of repeat injections is made at a particular injection site. Moreover, the best self-sealer, natural rubber latex, is known to have toxicity and blood clotting characteristics that are less desirable than other elastomeric materials such as silicone rubber, polyurethane elastomers, etc.

To overcome the leakage problem while concurrently avoiding toxicity or blood clot formation many injection site constructions have heretofore been proposed. Commercial tube sets have used a latex sleeve surrounding a section of the blood tubing and such site constructions rely on the inherent self-sealing of the latex sleeve to prevent leakage. To further insure against leakage, a similar construction surrounds the latex sleeve with a second thin, latex sleeve stretched over the first sleeve and extending beyond the ends of the first sleeve to also seal against the blood tube. This latter construction is shown in U.S.

Patent 3,814,137. While this construction has experienced some commercial acceptance, it is nevertheless subject to leakage under severe use conditions. It is further objectionable because of the hazard of piercing the holding hand of the person as the elastomeric sleeves and the tube are pierced.

A blood access site construction which purports to eliminate hazard to the needle administrator and leakage is shown in U.S. Patent 3,898,988. This construction employs a plastic tube section which is placed in the blood flow conduit. This plastic tube is a T-shaped hard plastic body having a bore extending for the length of the vertically disposed body portion and a diameter sufficient to receive the ends of blood which are adhesively secured in the bore. In the longitudinal central area of the tube the bore diameter equals the inner diameter of the blood tubes and the blood flows through the bore in the hard plastic tube in this area. Injection is made through a cylindrical opening in the top surface of the T-shaped tube, which opening extends down into the bore in the tube body through which.the blood is flowing; the opening is filled with a cylindrical insert of a non-thrombogenic elastomer such as polyurethane or silicone rubber which is compressed into place in the opening. This construction has the serious defects that the lower end of the elastomer is in contact with the blood flowing through the tube and the entire cylindrical elastomer insert is subject to dislodgement as the hypodermic needle is withdrawn; dislodgement of the entire elastomeric insert creates a channel for leakage having the same diameter as the blood tube diameter which is obviously unacceptable.

The above discussed constructions represent the closest prior art known to applicant which also includes the references cited during their prosecution which includ U.S. Patents 2,129,983; 2,498,831; 2,832,338; 3,030,955; 3,112,748; 3,447,570; 3,463,691; 3,853,127; 2,053,112, 2,907,351; and 3,566,868. None of the constructions known to applicant completely solve the problems of leakage into, or from, a non-thrombogenic blood tube while simultaneously eliminating the hazard of accidental piercing of the hand of the needle administrator.

The present invention solves both of these problems. According to the present invention the improved infusion tube access site comprises an infusion tube, an elongated elastomeric sleeve surrounding a portion of said infusion tube, and a needle-impenetrable C-shaped member surrounding said sleeve and extending substantially the full length and partially around the periphery thereof to thereby expose a portion of said sleeve between the inner extremities of the arms of said C-shaped member, said C-shaped member having an inner diameter smaller than the outer diameter of said sleeve and compressing said sleeve around said tube along the length thereof, the arm portions of said C-shaped member exerting a combination of radial and transversely directed forces within the portion of said elastomeric sleeve not covered by said C-shaped member sufficient to prevent leaks into said tube during the time a needle pierces said sleeve and said tube, and after withdrawal of said needle therefrom.

This invention provides an inexpensive infusion tube access site comprising a smooth nontoxic tube having an elongated elastomeric sleeve surrounding a section of the tube that is improved and distinguishes from prior constructions by a C-shaped needle-impenetrable member substantially co-extensive in length with the sleeve and enveloping more than one-half of the periphery of the elastomeric sleeve, which C-shaped member exerts a squeeze force on the sleeve which acts through the elastomeric properties of the sleeve to effectively seal against air leakage into, or blood leakage from, the blood tube during needle insertion or after the needle is withdrawn. The site construction of this invention protects against inadvertent injury to the hand holding the needle-impenetrable C-shaped member during needle insertion, and provides a large access area for making plural insertions while facilitating every angle of needle placement for injecting medications and collecting blood samples. The site construction of this invention also provides improved resistance to leaks under much more severe conditions of use than those normally encountered in the ordinary use of blood sets for blood passing between a patient and an artificial kidney or a blood oxygenator; it is also useful in transfusing blood or other fluids, such as saline solutions, etc.

Figure 1 is a top view of a preferred embodiment of the invention.

Figure 2 is a view taken on the line 2-2 of Figure 1.

Figure 3 is a view taken on the line 3-3 of Figure 2.

Figure 4 is a perspective view, partly broken away, showing the preferred embodiment during needle insertion.

Figure 5 is a view of the embodiment of Figure 4, in section, showing one needle piercing the elastomeric sleeve and blood tube wall and two additional piercing locations of a needle in dotted lines.

Figure 6 is a view illustrating a site of this invention which shows two withdrawn needle locations and a third needle partially withdrawn.

Figure 7 is an enlarged end view of the embodiment of Figure 1.

Figure 8 is an enlargement of the needle penetrating portion of Figure 7 showing the force distribution within the elastomeric sleeve as a needle is withdrawn.

Figure 9 is an enlargement of the portion of Figure 6 surrounded by the line 9-9 showing the force distribution within the elastomeric sleeve on a needle inserted at an angle less than 90" to the axis of the blood tube.

Referring to the drawings, the improved access site construction of this invention is shown in Figure 1 and generally designated 10. Site 10 consists of blood or infusion tube 12 which in normal use is a part of the blood tubing in a tube set which connects patient's artery or vein to an artificial kidney or blood oxygenator, or an organ perfusion device.

Tube 12 may be made of any of a number of commercially available nontoxic plastics, for example, polyvinyl plastisols, polyurethane or silicone rubber and preferably is made of plasticized polyvinyl chloride.

An elastomeric sleeve 14 surrounds a section of tube 12 at one or more locations along its length, for example, in sections about 1 to 21/2 inches long. The elastomeric properties of sleeve 14 are important to the accomplishment of the objective of elimination of leaks of the types above mentioned. The elastomer should be relatively soft and yet have sufficient elasticity and internal strength to permit needle insertion without shredding or disintegrating as the needle is inserted or withdrawn; it should exhibit maximized memory or ability to resume its original position after being stretched or deformed and maximum resistance to fatigue or change of resilience with reuse or passage of time. Importantly, the elastomer should be capable of transmitting forces, particularly compressive forces, from the point of application to the adjacent areas within the body of the elastomer. These general considerations can be employed in selecting the best elastomer for particular use conditions which may vary substantially as to pressure of fluid flowing in tube 12, or the diameter of the needle used, or the time of retention of the needle during the blood sampling or during the addition of medicants to the blood tube from those conditions which are normally encountered in the use of access sites on blood sets employed in dialyzing a patient with an artificial kidney. There are a number of types of elastomeric materials which are available from which sleeve 14 may be fabricated that will possess the appropriate degree of resiliency for a specific set of use conditions, for example, polyurethane elastomers, silicone elastomers, synthetic latex and natural rubber latex. For use in dialysis of humans employing an artificial kidney, particularly the type of artificial kidney containing hollow fibers as the dialyzing element such as the C-DAK artificial kidney available from Cordis Dow Corp., the preferred elastomer is natural rubber latex.

The third, and key, element in the preferred access site construction of this invention is a C-shaped needle-impenetrable element 16, which surrounds a portion of the periphery of sleeve 14, greater than one-half of that periphery, and preferably 65% to 90% of it.

Element 16 has its first function the prevention of inadvertent penetration by needle 18 completely through sleeve 14 and tube 12 and piercing the hand holding the access site as best illustrated in phantom in Figure 4. The second and more important function of C-shaped member 16 is to apply an amount of compressive force to the portion of sleeve 14 which it surrounds sufficient to enhance the inherent resiliency characteristics of that sleeve in the portion thereof which is not covered by member 16 to cause sleeve 14 to prevent air leaks into the tube 12 during the time that needle 18 is in penetrated position extending through the upper wall portions of sleeve 14 and tube 12 as may be seen in Figure 5.

Another somewhat less important function of member 16 is to continuously apply such an amount of force to and through the body of member 16 to cause substantially immediate blockage of fluid leaks outward through the opening in the tube 12 as needle 18 is drawn through the interface between the outer surface of the wall of tube 12 and the inner surface of sleeve 14, as is illustrated in Figure 6. Momentarily later, as needle 18 is withdrawn through the body, or upper wall, portion of sleeve 14, the force applied to sleeve 14 by member 16 functions to cause leak-tight closure of the opening earlier generated by the penetration of needle 18, as shown by lines 20, 22 in Figure 6. This latter force is applied majorly by the portions 16A, 16B of member 16, that is, the upper arm extremities which lie above a horizontal plane tangent to the upper surface of the tube 12 as shown by dotted line 17 in Figure 7.

The force applied by member 16 to sleeve 14 results from the strength of the material comprising member 16 to resist deformation from an original circular cross-section to the C-shaped cross-section it possesses when positioned around the portion of the periphery of sleeve 14 which it covers as shown in Figure 3 and 7. Figure 7 is an expanded end view of the preferred access site 10 which is drawn to scale and shows the degree to which member 16 is distorted from its original circular cross-section when the material of tube 12 is plasticized polyvinyl chloride, elastomeric sleeve 14 is natural rubber latex and member 16 is polypropylene. Before assembly, tube 12 had an outside diameter of 0.253" + 0.003"; latex sleeve 14 had an inner diameter of 0.219" + 0.016", a wall thickness of 0.125" + 0.010" and a nominal outside diameter of 0.469". Sleeve 14 is mounted over tube 12 and its inner diameter is slightly stretched as it moves into position over the section of tube 12 preselected as the location for access site 10 and sleeve 14 concurrently applies a small compressive force on the outer diameter of tube 12. Similarly, prior to assembly, member 16 was an injection molded polypropylene member, circular in cross-section, having an inner diameter of 0.400" and a wall thickness of 0.052-0.060" and an opening between the upper wall portions 16A and 16B of 0.125" as shown in Figures 3 and 7. Member 16 is mounted on sleeve 14 by forcing the portions 16A and 16B apart sufficiently to enable encirclement of the outside diameter of sleeve 14; the resistance of the polypropylene material to the spreading deformation sufficient to tightly overlie the illustrated portion of the periphery of sleeve 14 results in a bulging of the portion indicated by arrow 23 of sleeve 14 which lies between the inner surfaces 24A and 24B. Due to the final position spreading of arm portions 16A and 16B during assembly the portion indicated by arrow 25 of the wall of member 16 is slightly flattened from its circular cross-section producing a slightly elongated C-section which may be seen by rotating Figure 7 until portion 16B is at the top of the figure.

As a result of the distortion of member 16 from its initial circular cross-section a combination of multi-directional forces are constantly applied to sleeve 14 by member 16.

These forces are illustrated by the arrows 26 in Figure 8 and are related to a needle 18 which is piercing sleeve 14 perpendicularly to the longitudinal axis of tube 12. It may be seen that the forces applied, primarily by the upper wall portions 16A and 16B, comprise forces consisting of components directed radially inwardly toward sleeve 12 and other forces which result from the squeezing pressure of surfaces 24A, and 24B on the outer surface of sleeve 14 to cause the bulging at 23 which have components which vary from the radial direction gradually upwardly to the horizontal and beyond toward the axially central area of the bulge 23.

Figure 9 specifically illustrates the distribution of forces which are additionally available to cause closure, and leak-tight sealing, of a needle inserted through sleeve 14 at an angle less than 90 , and about 40 as shown, from a horizontal plane passing through the axis of tube 12, as indicated at 28, Figure 6. Arrows 30 show the vertically oriented forces which bear on the upper and lower surface portions of the opening cause by needle 18 due to the angular insertion of the needle. The best sealing results are obtained with the access site construction of this invention when the needle penetration is made at an angle of approximately 45" Ifr 100 from a horizontal plane passing through the axis of tube 12. The access site shown in Figure 7 and constructed from the materials above identified represents the best form of the invention that is currently known. It is satisfactory, however, to fabricate member 16 from materials other than polypropylene. The important requirement which must be satisfied is that the substitute material possess a relatively high rigidity and resistance to deformation from an initial circular cross-section to a C-shaped cross-section similar to that above described for polypropylene member 16. It is desirable to select a substitute having sufficient resistance to deformation in a relatively thin wall section, for example, less than 0.100", to exert sufficient force to insure against leaks under severe use conditions. Satisfactory substitutes for polypropylene include other plastics such as synthetic polyamides available under the designation "Nylon", acetal resins available under the registered Trade Mark "Delrin", and ABS resins available from many suppliers; metals such as steel, stainless steel, aluminium and magnesium may be used and are recommended for use under the most severe of use conditions. Metal offers the advantage of ease of fabrication into initial cross-sectional forms other than circular to enable increased pressure from the upper wall portions corresponding to 16A and 16B. For example, portions 16A and 16B may be initially bent inwardly from the circular so as to exert additional downward forces to those illustrated as arrows 26 in Figure 8.

The improvement in preventing air leaks using the preferred embodiment of this invention which has been specifically described above as to materials, initial and assembled sizes in the description of Figure 7 is illustrated by the comparative test data set forth below.

The preferred access site of this invention was tested in comparison with the access site construction of U.S. patent 3,814,137 which is commercially available from Travenol Laboratories, Inc. under the designation Travenol Dialysis Blood Set. Each of these constructions is especially suitable for use in blood sets employed in artificial kidney dialysis, and thus the test conditions selected for the comparison are conditions which are much more severe than the conditions encountered in normal clinical use on actual dialysis patients. The test conditions used are shown in Table I to provide a comparison with normal conditions encountered in clinical usage during dialysis employing a hollow fiber C-DAK artificial kidney.

TABLE I Selected Test Clinical Dialysis Condition Normal Range Needle 18 gauge (0.05" diameter) 20-27 gauge (0.036 0.016" diameter) Angle of piercing 90" 45" Pressure, sub atmospheric -150 to -400 mm Hg 0 to -80 mm Hg Pressure, positive 5, 10, 15 psig 0.4 - 3.0 psig Fluid Flow Rate 200 ml/minute 100 - 300 ml/minute Temperature 37"C t 1"C 35"C - 39"C Fluid Water Blood It will be apparent that the conditions of larger needle size, angle of piercing, pressures both negative and positive and the use of water rather than blood are each substantially more severe than use conditions normally encountered.

The test procedure used was as follows: 1. Connect blood lines to negative pressure system and warm to body temperature, 370C.

2. At water flow rate of 200 ml/min. set pressure to -150 mm Hg, which is approximately twice the maximum negative pressure usually encountered in dialysis.

3. Using 18 gauge, 0.050" diameter, needle pierce through the latex sleeve and the tube at a 90" angle to a horizontal plane passing through the axis of the blood tubes and hold in place for 1 minute, withdraw and inspect for leaks under bright light. If no leak, after 1 minute, then repeat and reinspect.

4. If no leak is visible after second inspection, raise subatmospheric pressure on water to -400 mm Hg. Repeat Step 3 for 2 piercings with 1 minute held before inspection.

5. If no leak after the four piercings of Steps 3 and 4, set pressure on water to positive 5 psig and repeat Step 3.

6. If no leak after the sixth piercing in Step 5, change pressure to positive 10 psig and repeat Step 3.

7. If no leak after the eighth piercing of Step 6, change pressure to positive 15 psig and repeat Step 3. At any time a leak appeared in the form of a visible bubble or bubbles in the water in the Steps 3 or 4 or a leak around the needle or at the needle opening after withdrawal and after 1 minute of of inspection time, the test was stopped and the number of piercings made before the leak occurred was recorded and the test discontinued.

Twenty access site constructions of the type shown in Figure 2 of U.S. Patent 3,814,137, available in the United States under the designation Travenol Dialysis Blood Set were obtained and tested under the selected test conditions by using the above stated test procedure in comparison to the preferred acces site constructions of this invention specifically shown in Figure 7 and described above as to dimensions. The results are reported as the average number of needle punctures before a leak occurred, following for each access site the sequence of puncturing under the increasingly severe test conditions until failure occurred. The average number of punctures before a leak occurred for the access site constructions of U.S. Patent 3,814,137 for the 20 sites tested was 5.25. The average number of punctures before a leak occurred for the preferred access site constructions of this invention for the 72 sites tested was 7.66.

To illustrate the necessity for sufficient forces to be generated by the needleimpenetrable sleeve within the body of the latex sleeve to prevent leaks, and for contrast with the results obtained from the use of the preferred embodiment of this invention as above shown, a further series of tests was conducted. In this series, each of the tube, the latex sleeve and the needle-impenetrable member was made of the same material as was used in the test of the preferred embodiment. The only change was the size of the latex sleeve, and it was decreased to an outside diameter of 0.438" and its inner diameter was 0.187". This change decreased the difference in diameter between the latex sleeve outside diameter and the impenetrable member inside diameter and concurrently increased the difference in outside diameter of the tube and the inside diameter of the latex sleeve.

Seventy-two access sites of this construction, tested under identical conditions and by the same procedure resulted in an average number of punctures to leak of 2.53.

WHAT WE CLAIM IS: 1. An infusion tube access site assembly comprising an infusion tube, an elongated elastomeric sleeve surrounding a portion of said infusion tube, and a needle-impenetrable C-shaped member surrounding said sleeve and extending substantially the full length and partially around the periphery thereof to expose thereby a portion of said sleeve between the inner extremities of the arms of said C-shaped member, said C-shaped member having an inner diameter smaller than the outer diameter of said sleeve and compressing said sleeve around said tube along the length thereof, the arm portions of said C-shaped member exerting a combination of radial and transversely directed forces within the portion of said elastomeric sleeve not covered by said C-shaped member sufficient to prevent leaks into said tube during the time a needle pierces said sleeve and said tube, and after withdrawal of said needle therefrom.

2. An assembly as claimed in claim 1, in which the infusion tube is made of a non-toxic material of the plastics class.

3. An assembly as claimed in claim 1 or claim 2 in which the infusion tube is fabricated from a polyvinyl chloride polymer.

4. An assembly as claimed in any one of claims 1 to 3, in which the elastomeric sleeve is made of natural rubber.

5. An assembly as claimed in any one of claims 1 to 4 in which the C-shaped member is polypropylene.

6. An assembly as claimed in any one of claims 1 to 5 in which the C-shaped member extends around more than one half of the periphery of the sleeve.

7. An assembly as claimed in claim 6 in which the C-shaped member extends around from 65% to 90% of the periphery of the sleeve.

8. An assembly as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. difference in outside diameter of the tube and the inside diameter of the latex sleeve. Seventy-two access sites of this construction, tested under identical conditions and by the same procedure resulted in an average number of punctures to leak of 2.53. WHAT WE CLAIM IS:

1. An infusion tube access site assembly comprising an infusion tube, an elongated elastomeric sleeve surrounding a portion of said infusion tube, and a needle-impenetrable C-shaped member surrounding said sleeve and extending substantially the full length and partially around the periphery thereof to expose thereby a portion of said sleeve between the inner extremities of the arms of said C-shaped member, said C-shaped member having an inner diameter smaller than the outer diameter of said sleeve and compressing said sleeve around said tube along the length thereof, the arm portions of said C-shaped member exerting a combination of radial and transversely directed forces within the portion of said elastomeric sleeve not covered by said C-shaped member sufficient to prevent leaks into said tube during the time a needle pierces said sleeve and said tube, and after withdrawal of said needle therefrom.

2. An assembly as claimed in claim 1, in which the infusion tube is made of a non-toxic material of the plastics class.

3. An assembly as claimed in claim 1 or claim 2 in which the infusion tube is fabricated from a polyvinyl chloride polymer.

4. An assembly as claimed in any one of claims 1 to 3, in which the elastomeric sleeve is made of natural rubber.

5. An assembly as claimed in any one of claims 1 to 4 in which the C-shaped member is polypropylene.

6. An assembly as claimed in any one of claims 1 to 5 in which the C-shaped member extends around more than one half of the periphery of the sleeve.

7. An assembly as claimed in claim 6 in which the C-shaped member extends around from 65% to 90% of the periphery of the sleeve.

8. An assembly as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.