Valved blunt cannula injection device

Abstract: An infusion site for infusing fluids into a patient is disclosed. The infusion site has a housing (12) which supports a pre-slit resealable septum (26) which is held in radial compression in the housing (12). The septum (26) is opened by the insertion of a cannula (60). The housing also accommodates a valve (44) which is held in tension in the housing and is opened by the insertion of the cannula (60) into the septum (26). The valve (44) is closed when the cannula (60) is withdrawn. The septum (26) and valve are linked by an elastic member (34) which interacts with the cannula (60) open and close the valve (44).

Description: BACKGROUND OF THE INVENTION The invention generally relates to medical infusion devices. In particular, it relates to injection or infusion sites for infusing liquids into a patient. During the course of medical treatment, it is often necessary to infuse medicinal or nutritional fluids into a patient. It may be necessary to infuse such substances repeatedly or over extended time periods. This is usually done by inserting an indwelling catheter into the body, often the vasculature. Fluids may then be infused repeatedly without the need for repeated piercing of the skin, veins or arteries and the trauma associated with such procedures. Such an indwelling catheter is typically provided with an injection or infusion site which allows a needle or cannula to be inserted and withdrawn as needed so that fluids can be infused through the catheter. Such an injection or infusion site is known as a "PRN" or "pro re nata" (from the Latin for "as the occasion arises") site. PRN sites are well known in the art. The most commonly used PRN comprises a rubber or silicone septum. Such a PRN is used by penetrating the septum with a hypodermic needle to infuse the fluid. On withdrawal of the needle, the septum reseals itself due to the elasticity of the septum and the fact that the hole made by piercing the septum is very small. In recent years concern has grown about the risks of infection to health care workers presented by sticks by contaminated needles. Attempts have been made to provide protective shields for needles specifically used for intravenous infusion. U.S. Patent No. 5,084,032 shows an example of such a system. Another approach is to provide an injection site which shields the nurse or doctor's fingers. An example of this approach is shown in U.S. Patent No. 5,078,694. A further approach to avoiding needle sticks resulting from the use of intravenous infusion sets is to use an infusion site having a pre-split septum in conjunction with a blunt cannula rather than one requiring the septum to be pierced by a sharp needle. Examples of this approach are found in International Patent Applications published under the Patent Cooperation Treaty under International Publication Nos. WO 89/06553 and WO 90/11103. SUMMARY OF THE INVENTION Specifically, the invention relates to an infusion device having the characteristics called for in the preamble of Claim 1. Such a device is known, e.g from WO 92/04936. A pre-slit injection site is also shown in WO 91/05581. The invention is a device for facilitating the infusion of fluids into a patient by means of a blunt cannula. The device of the invention, having the further features called for in Claim 1, has a housing for carrying a pre-split septum. Attached to the septum is a valve which is opened by the insertion of a cannula into the septum. The septum re-seals itself and the valve closes when the cannula is withdrawn. Thus two barriers are provided against bacterial and viral infection and the need for a sharp needle is averted. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of the invention prior to the insertion of a cannula; Fig. 2a is a bottom view of the invention showing the slit in the septum viewed from point 2a in Fig. 1; Fig. 2b is a bottom view of an alternative embodiment of the invention having a multi-armed slit in the septum viewed from point 2a in Fig. 1. Fig. 3 is a top view of the invention through section 3-3; Fig. 4 is a cross-sectional view of the invention showing the septum penetrated by a cannula. DETAILED DESCRIPTION Valve housing 12 having proximal end 14, distal end 16 and lumen 18 extending between the proximal and distal ends defines the outer casing of device 10. Valve housing 12 is provided with female luer lock type connector 20 at proximal end 14 and male luer type connector 22 at distal end 16. Valve housing 12 and luer type connectors 20 and 22 are injection moulded out of polycarbonate, preferably General Electric Lexan HP ("Health Products"). Male luer type connector 22 and valve housing 12 are separately injection molded and then joined preferably by sonic welding. Solvent bonding may also be used to join them. Distal end 16 is slightly enlarged in diameter relative to body section 24 of valve housing 12. Distal end 16 has a generally frusto-conical shaped section 17. Pre-split resealable septum 26 is housed at proximal end 14. Septum 26 is provided with slit 28. Slit 28 is shown as a single cut in septum 26 (Fig. 2a), but may be in the form of a multi-armed cut such as a three armed cut 128, the arms 129, 130, 131 being at 120° to each other (Fig. 2b). Septum 26 is held in place by an interference fit between septum 26 and valve housing 12 at lip 30. Septum 26 provides an anti-bacterial seal, preventing the entry of contaminants into valve housing 12. Proximal end 14 may also be provided with flange 32 to hold septum 26 in place. Irrespective of whether septum 26 is held in place by lip 30 or flange 32, septum 26 is held in compression in valve housing 12. The forces exerted by housing 12 on septum 26 are thus directed radially towards the center of septum 26 and cause slit 28 to tend to remain sealed. Septum 26 is made of an elastically deformable thermoset elastomer, preferably Dow Corning Medical Grade Injection Mouldable silicone rubber available from Dow Corning under product number Q7-4850 (durometer 50 Shore A). Septum 26 is injection molded. The properties of this elastomer are such that slit 28 tends to remain closed unless forced open by the insertion of a cannula or similar object. Extending towards the distal end 16 of valve housing 12, inside lumen 18 is an elastic extension 34 to septum 26. Extension 34 is preferably integral with and made of the same material as septum 26. Extension 34 defines lumen 36 within lumen 18 of valve housing 12. The walls of extension 34 are dimensioned so that inside diameter d of lumen 36 is slightly smaller than outside diameter D of the tip of cannula 60 (Fig. 3). Extension 34 has a distal end 38. Distal end 38 of extension 34 has a generally frusto-conically shaped section 35 designed to mate with inner surface 40 of frusto-conically shaped section 17 of valve housing 12 thereby providing a pressure seal. Septum 26 and extension 34 are held in tension in valve housing 12 so that distal end 38 tends to push against surface 40, thus keeping surfaces 40 and 42 in sealing engagement. Distal end 38 is provided with valve cap 50 which closes off open end 48 extension 34. Adjacent distal end 38, extension 34 is provided with valve windows 44. As shown in Fig. 1, when surfaces 40 and 42 are in contact, valve windows 44 are closed by wall 46 of valve housing 12. A seal is created by the pressure of surface 40 against surface 42. Thus, a fluid-tight resealable valve is provided between valve housing 12 and extension 34. Valve cap is preferably made of General Electric Lexan HP2 and is held in place at distal end 38 by an interference fit. Cannula 60 is shown inserted into septum 26 in Fig. 4. The insertion of cannula 60 splits septum 26 and deforms the material of septum 26. Since septum 26 is constrained by the walls of valve housing 12, and cannula 60 frictionally engages the inner walls of extension 34, the insertion of cannula 60 pushes extension 34 towards distal end 16 of valve housing 12 as shown in Fig. 4. The stretching of extension 34 causes surface 42 of distal end 38 to move out of engagement with surface 40 and causes valve windows 44 to be opened to chamber 52 due to the enlarged diameter of lumen 18 in the region of distal end 16. Once valve windows 44 are opened to chamber 52, fluid can flow from lumen 36 into chamber 52, through lumen 56 and into the patients vasculature as shown by arrows 58 in Fig. 4. If cannula 60 is inserted sufficiently far into valve housing 12, valve cap 50 will abut surface 54 of luer connector 22. In order to ensure that fluid flows into lumen 56 of luer connector 22, valve cap 50 is provided with fluid channels 52 as shown in Fig. 3. When cannula 60 is withdrawn, the elasticity of extension 34 and the fact that septum 26 and extension 34 are held in tension in valve housing 12 cause surface 42 of distal end 38 to revert to engagement with surface 40, thus re-closing valve windows 44. When cannula 60 is fully withdrawn, septum 26 will reclose due to the mechanical properties of the material of septum 26 and the fact that septum 26 is radially compressed in housing 12.

Claims: An infusion device for permitting selective infusion of fluid into a patient by means of a blunt cannula, the infusion device comprising: a housing (12) having a proximal end (14) and a distal end (16) and a lumen (18) therebetween; a septum (26) supported by the housing at the proximal end of the housing, the septum having a re-sealable slit means (28) for permitting entry of the cannula; valve means (44) and actuating means (34) actuable by entry of the cannula (60) into the slit for opening and closing the valve means, the actuating means being actuable by insertion of the cannula into the septum, characterized in that said actuating means (34) has a proximal end and a distal end and is connected at its proximal end to the septum (26) and at its distal end to the valve means for selectively permitting fluid flow through the lumen. The infusion device of Claim 1 wherein the actuating means for opening and closing is an elastic member (34) connecting the valve means to the septum. The infusion device of claims 2 wherein the elastic member (34) is housed in the housing (12). The infusion device of claims 2 or 3 wherein the septum (26) is held in radial compression in the housing (12). The infusion device of claims 2, 3, or 4 wherein the elastic member (34) is held in tension in the housing (12).

Inventors: BRIMHALL GREGORY LEE, ERSKINE TIMOTHY JOSEPH, STEINMAN CHRISTOPHER PAUL, BRIMHALL, GREGORY LEE, ERSKINE, TIMOTHY JOSEPH, STEINMAN, CHRISTOPHER PAUL
Applicants: BECTON DICKINSON CO, BECTON DICKINSON AND COMPANY
Application year: 1993
Main classification: A61M39
IPC codes: A61M39, A61M5