Injection apparatus with needle housing for desensitising skin

Abstract

A needle housing having a distal end which is removably connectable to a source of injectable fluid and a proximal end for contacting a patient, as well as to an injection apparatus comprising the needle housing. The needle housing comprises (a) a hollow needle through which the injectable fluid is deliverable to the patient, the needle having a proximal end for insertion into body tissue of the patient, and (b) a chamber having an open proximal end, the chamber surrounding at least part of the needle and extending proximally beyond the proximal end of the needle to the open proximal end. The open proximal end of the chamber is deformable and is moveable relative to the needle from a position in which the chamber extends proximally beyond the proximal end of the needle to a position in which the proximal end of the needle extends proximally through the open proximal end of the chamber.

Claims

1. A needle housing having a distal end which is removably connectable to a source of injectable fluid and a proximal end for contacting a patient, the needle housing comprising: a) a hollow needle through which the injectable fluid is deliverable to the patient, the needle having a proximal end for insertion into body tissue of the patient; and b) a chamber having an open proximal end, the chamber surrounding at least part of the needle and extending proximally beyond the proximal end of the needle to the open proximal end, wherein the open proximal end of the chamber comprises a lip which is deformable and resiliently sealable against the body tissue of the patient, and wherein the open proximal end is moveable relative to the needle from a position in which the chamber extends proximally beyond the proximal end of the needle to a position in which the proximal end of the needle extends proximally through the open proximal end of the chamber, wherein the needle housing comprises a closable gas permeable section which connects the chamber to an exterior of the housing but is not permeable to the injectable fluid.

2. The needle housing as claimed in claim 1, wherein the chamber is collapsible and deformable.

3. The needle housing as claimed in claim 1, wherein the chamber and the open proximal end comprises a deformable plastic.

4. The needle housing as claimed in claim 3, wherein the chamber is collapsible and deformable to an extent that, in use, allows the needle to pierce the body tissue of a patient.

5. The needle housing as claimed in claim 1, wherein the proximal end of the needle is bevelled.

6. The needle housing as claimed in claim 1, comprising a substantially rigid connector at its distal end.

7. The needle housing as claimed in claim 1, wherein the needle housing is connectable to the source of injectable fluid by an interference fitting, a friction fitting, a Luer lock, or a screw thread.

8. The needle housing as claimed in claim 1, wherein the needle has a distal end which protrudes distally at the distal end of the housing.

9. The needle housing as claimed in claim 8, wherein the distal end of the needle is bevelled.

10. The needle housing as claimed in claim 1, wherein the needle is bent.

11. The needle housing as claimed in claim 10, wherein the needle is bent through an angle of at least 30 degrees.

12. The needle housing as claimed in claim 1, wherein the chamber is substantially bell-shaped.

13. The needle housing as claimed in claim 1, wherein the proximal end of the needle housing additionally comprises an end cap which is removably attachable to the open proximal end of the chamber.

14. The needle housing as claimed in claim 1, wherein the source of injectable fluid comprises a syringe.

15. The needle housing as claimed in claim 1, wherein the injectable fluid comprises a local anaesthetic.

16. The needle housing as claimed in claim 1, wherein the open proximal end of the chamber has an area of 3.5 square centimeters or less.

Description

(1) This invention will be further described by reference to the following Figures which are not intended to limit the scope of the invention claimed, in which:

(2) FIG. 1 shows a needle housing in accordance with one embodiment of the invention when part of an injection apparatus.

(3) FIG. 2 shows an enlarged view of the proximal end of the injection apparatus of FIG. 1.

(4) FIG. 3 shows an exploded view of the proximal end of the injection apparatus of FIG. 1 and a cartridge of injectable fluid.

(5) FIG. 4 shows an enlarged view of the needle housing of FIG. 1.

(6) FIG. 5 shows an alternative embodiment of a needle housing in accordance with the invention in which the needle is straight.

(7) FIG. 6 shows the needle housing of FIG. 5 and an alternative source of injectable fluid in accordance with the invention.

(8) FIGS. 7A-D show various types of needle housing and sources of injectable fluid in accordance with the invention.

(9) FIG. 1-4 depict a needle housing 15 in accordance with one embodiment of the invention. In FIGS. 1-3, the needle housing 15 is shown as part of an injection apparatus 1. The injection apparatus 1 comprises a breech-loading syringe 10 which is connected at its proximal end 11 to the needle housing 15. The needle housing comprises a deformable chamber 75 which surrounds and extends proximally beyond a needle 5. The injection apparatus 1 has a major axis A which is parallel to the syringe 10.

(10) As shown in FIGS. 1-3, the syringe 10 comprises a cylindrical tube 12 and a plunger 20 (only shown in FIG. 1) which is slidably fitted within the tube 12. The cylindrical tube 12 is made mainly of metal (but alternatively could be made of a disposable plastic material), but with two slots 13 provided in opposite sides of the tube 12. The slots 13 are provided to assist the user in determining the position of the plunger 20 within the cylindrical tube 12.

(11) As shown in FIG. 1, at its distal end 14 the syringe 10 is provided with two syringe finger grips 16,17. Syringe finger grips 16,17 are in the form of metal tabs which extend in opposite directions from syringe 10 and substantially perpendicularly to the major axis A of injection apparatus 1. Syringe finger grips 16,17 are provided to make it easier for the user to hold the injection apparatus 1.

(12) As is known in the art, cylindrical tube 12 is shaped to accept cartridges of fluid (in particular a liquid) comprising a local anaesthetic. An example of such a cartridge 40 is shown in FIG. 3. The cartridge 40 comprises a metal cap 45 which is provided with a latex-free membrane (not shown) on a proximal surface 46 for piercing by the needle 5. The cartridge 40 also comprises a glass phial 50 which contains the fluid. Slidably fitted within glass phial 50 is bung 51 (shown in FIG. 1).

(13) As also shown in FIG. 1, the plunger 20 comprises a solid cylindrical rod 21 which is slidably fitted within cylindrical tube 12. At the distal end 22 of rod 21 is provided a palm rest. The palm rest is in the form of metal tabs 24,25 which extend in opposite directions from rod 21 substantially perpendicularly to the major axis A of injection apparatus 1. The palm rest is designed to rest against the user's palm during use in order to make it easier for the user to hold the injection apparatus 1.

(14) As is known in the art, the solid cylindrical rod 21 of plunger 20 is shaped such that in use its proximal end 23 abuts slidable bung 51.

(15) The needle 5 of needle housing 15 is a hypodermic needle which, as is known in the art, comprises a hollow metal tube 30 with a proximal bevelled tip 35 (see FIGS. 1-4). The proximal bevelled tip 35 makes it easier for the user to pierce the body tissue of the patient who is to receive the injection.

(16) The needle 5 is connected to, and passes through the centre of, solid rigid annular plastic collar 55 of needle housing 15. The collar 55 has an internal cylindrical cavity at its distal end 56 which is provided with a screw thread (not shown). The screw thread on the collar 55 is shaped to cooperate with external screw thread 60 (see FIG. 3) provided at the proximal end 11 of syringe 10. The collar 55 also has depression 66 which the user can press with their finger during use in order to deform the deformable chamber 75.

(17) As shown in FIGS. 1-4, the needle 5 protrudes distally from collar 55 and is provided with a distal bevelled tip 65 which is substantially identical in shape to proximal bevelled tip 35. As shown in FIGS. 1 and 2, when the collar 55 is screwed onto external screw thread 60 of syringe 10, the needle extends distally within cylindrical tube 12 of syringe 10 such that when a cartridge 40 is fitted within the tube 12 the distal bevelled tip 65 pierces the latex-free membrane and contacts the fluid within the cartridge 40.

(18) The needle 5 initially extends proximally through collar 55 within needle housing 15 in a direction coincident with major axis A of the injection apparatus 1. At approximately halfway between the proximal end 11 of syringe 10 and the proximal bevelled tip of needle 5, the needle 5 is bent in a direction approximately 45 to major axis A. The bend in needle 5 is not essential, but is particularly useful for applications in dental surgery where it can assist the user in accessing certain parts of a patient's mouth.

(19) Extending proximally from collar 55 and surrounding needle 5 is deformable chamber 75 of needle housing 15. Deformable chamber 75 is normally made of a transparent deformable plastic such as silicone. Deformable chamber 75 is formed around the part of needle 5 which is bent in a direction approximately 45 to major axis A.

(20) Deformable chamber 75 has a domed distal end 74 and it curves outwardly at its proximal end 80 to form lip such that chamber 75 is substantially bell-shaped. The proximal end 80 of deformable chamber 75 extends proximally beyond the proximal bevelled tip 35 of needle 5 such that, if proximal end 80 was rested on a flat surface (without applying pressure to deform the deformable sleeve 15), the proximal bevelled tip 35 of needle 5 would not contact the surface.

(21) As shown in FIGS. 1-4, the proximal end 80 of deformable chamber 75 is provided with a removable end cap 85 (shown in section). The end cap is made of a deformable material such as a deformable plastic or latex-free material and comprises a circular base 90 and an annular wall 95. The annular wall 95 is provided at its edge 100 with an annular lip 105. The annular lip 105 is shaped to grip the outward curve of proximal end 80 of deformable chamber 75.

(22) During use, the part of the patient's body tissue where the injection is to take placed is first cleaned with an antiseptic swab. A cartridge 40 of local anaesthetic-containing fluid is then placed in cylindrical tube 12 of syringe 10. Plunger 20 is then inserted into the cylindrical tube such that its proximal end 23 abuts slidable bung 51. Needle housing 15 is then connected to syringe 10 by screwing collar 55 onto external screw thread 60 at proximal end 11 of syringe 10 such that distal bevelled tip 65 of needle 5 pierces the latex-free membrane of cartridge 40.

(23) The proximal end 80 of deformable chamber 75 of needle housing 15 is then placed in contact with the part of a patient's body tissue where the injection is to take place. In dental surgery, this is commonly a part of the patient's oral mucosa. In this way, the chamber 75 is substantially resiliently sealed by deformation at its proximal end 80 against the patient's body tissue. At this stage in the procedure, the proximal bevelled tip 35 of needle 5 is not in contact with the patient's body tissue.

(24) The plunger 20 of syringe 10 is then slid in a proximal direction, which causes bung 51 to slide in a proximal direction, such that the anaesthetic-containing fluid flows into distal bevelled tip 65 of needle 5, along hollow metal tube 30 and out from proximal bevelled tip 35. As a result of chamber 75 being substantially sealed, the chamber 75 fills with the local anaesthetic-containing fluid. The chamber 75 may be adjusted slightly during filling in order to allow air to escape and be replaced in the chamber 75 by the local anaesthetic-containing fluid.

(25) Once chamber 75 has been filled with the local anaesthetic-containing fluid, the user attempts to slide the plunger 20 further in a proximal direction such that the local anaesthetic-containing fluid in chamber 75 is pressurised. Alternatively or additionally, the fluid can be pressurised by at least partially collapsing and/or deforming the chamber 75. This helps the local anaesthetic-containing fluid to be absorbed through the part of the patient's body tissue that it is in contact with. The injection apparatus 1 is held in this position for a period of time, normally at least 30 seconds or more, such that the absorption of the local anaesthetic causes a sufficient degree of numbness to develop in the patient's body tissue. The part of the patient's body tissue which absorbs the anaesthetic-containing fluid can sometimes swell at this stage such that the distance between the patient's body tissue and the proximal bevelled tip 35 of needle 5 is reduced.

(26) Force is then applied by the user to the injection apparatus 1 such that the deformable chamber 75 deforms and the proximal bevelled tip 35 of needle 5 pierces the patient's body tissue. Force may additionally be applied by the user by pressing the depression 66 of the collar 55. The anaesthetic-containing fluid remaining in cartridge 40 is then injected into the patient in the normal way known in the art.

(27) By following the method described above, the pain and discomfort felt by the patient due to the piercing of the patient's body tissue by the needle and/or by the motion of the fluid as it is delivered through the needle to the patient is substantially reduced. This is achieved by causing the anaesthetic-containing fluid to initially be absorbed by the patient's body tissue prior to carrying out the injection.

(28) FIGS. 5 and 6 depict an alternative needle housing 115 in accordance with the present invention, shown as part of injection apparatus 101. Features in common with the embodiment shown in FIGS. 1-4 are labelled with the same reference numerals.

(29) The main difference between the needle housing 115 of FIGS. 5 and 6 and the needle housing 15 of FIGS. 1-4 is that the needle 5 of needle housing 115 is straight. Thus, needle 5 extends proximally through collar 55 and into deformable chamber 75 in a direction coincident with major axis A (shown in FIG. 6) of injection apparatus 1. In addition, collar 55 does not comprise depression 66 and the deformable chamber 75 comprises gas permeable section 76. Gas permeable section 76 could be replaced by a vent as described above.

(30) The injection apparatus 101 of FIGS. 5 and 6 also differs from the injection apparatus 1 of FIGS. 1-4 in that it comprises a collapsible local anaesthetic container 110, instead of a syringe 10, which is connectable at its proximal end 111 to needle housing 115.

(31) As shown in FIGS. 5 and 6, the container 110 is provided with an external screw thread 160 which is shaped to cooperate with a screw thread in internal cylindrical cavity at proximal end 56 of collar 55. FIG. 5 only shows the proximal end 111 of container 110, whereas FIG. 6 shows the whole container 110.

(32) Collapsible compartment 145 (shown in sectional view in FIG. 6) extends distally from external screw thread 160. Compartment 145 contains a liquid comprising a local anaesthetic. Compartment 145 is generally cylindrical in shape and has a concertina wall 120. The wall is formed from a deformable plastic such as silicone.

(33) At proximal end 125 of compartment 145 are provided two finger grips 130,131. Finger grips 130,131 are in the form of two rigid plastic tabs which extend in opposite directions from compartment 145 substantially perpendicularly to the major axis A of injection apparatus 101. Figure grips 130,131 are provided to make it easier for the user to hold injection apparatus 101.

(34) Also at proximal end 125 of compartment 145, and between compartment 145 and external screw thread 160, is provided latex-free membrane 140.

(35) In use, needle housing 115 is connected to container 110 by screwing collar 55 onto external screw thread 160 at proximal end 111 of container 110 such that distal bevelled tip 65 of needle 5 pierces latex-free membrane 140. In this way, distal bevelled tip 65 of needle 5 is brought into contact with the local anaesthetic-containing liquid within container 110.

(36) The proximal end 80 of deformable chamber 75 of needle housing 115 is then placed in contact with the part of a patient's body tissue where the injection is to take place. In this way, the chamber 75 is substantially resiliently sealed by deformation at its proximal end 80 against the patient's body tissue. At this stage in the procedure, the proximal bevelled tip 35 of needle 5 is not in contact with the patient's body tissue.

(37) Pressure is then applied to compartment 145 of container 110 such that the concertina wall 120 begins to collapse. This causes the anaesthetic-containing liquid to flow into distal bevelled tip 65 of needle 5, along hollow metal tube 30 and out from proximal bevelled tip 35. As a result of chamber 75 being substantially sealed, the chamber 75 fills with the local anaesthetic-containing liquid. Any air in chamber 75 can escape via gas permeable section 76. However, since gas permeable section 76 is not permeable to the local anaesthetic-containing liquid, this liquid is retained in the chamber. Gas permeable section 76 could be replaced with a vent.

(38) Once chamber 75 has been filled with the local anaesthetic-containing liquid, the user applies further pressure to the compartment 145 of container 110. This causes the concertina wall 120 to collapse further such that the local anaesthetic-containing fluid in chamber 75 is pressurised. This causes the local anaesthetic-containing fluid to be absorbed through the part of the patient's body tissue that it is in contact with. The injection apparatus 101 is held in this position for a period of time, normally at least 30 seconds or more, such that the absorption of the local anaesthetic causes a sufficient degree of numbness to develop in the patient's body tissue. The part of the patient's body tissue which absorbs the anaesthetic-containing fluid can sometimes swell at this stage such that the distance between the patient's body tissue and the proximal bevelled tip 35 of needle 5 is reduced.

(39) Force is then applied by the user to the injection apparatus 101 such that the deformable chamber 75 deforms and the proximal bevelled tip 35 of needle 5 pierces the patient's body tissue. The anaesthetic-containing liquid remaining in compartment 145 of container 110 is then injected into the patient by applying additional pressure such that concertina wall 120 to collapses further. Once the area of the patient's body tissue has been anaesthetised, the container 110 can optionally be disconnected and an alternative container (not shown) can be connected to needle housing 115. The alternative container may contain other medications, such as antibiotics, which can then be injected into the patient substantially painlessly.

(40) FIGS. 7A-D depict various types of needle housing and sources of injectable fluid in accordance with the invention. FIG. 7A shows an external view of the container 110 and needle housing 115 depicted in FIG. 6. The features of FIG. 6 in common with FIG. 7A are identically labelled in FIG. 7A. Only the distal end 56 of needle housing 115 is shown in FIG. 7A.

(41) FIG. 7B shows the breech-loading syringe 10 of the embodiment of the invention depicted in FIG. 1 for connection with the needle housing 115 shown in FIGS. 5, 6 and 7A. The features of FIGS. 1, 5, 6 and 7A in common with FIG. 7B are identically labelled in FIG. 7B.

(42) FIG. 7C shows a needle housing 215 for connection with a plastic syringe 200 with a male Luer lock fitting 210 at its proximal end. The plastic syringe 200 comprises a cylindrical tube 212 and a plunger 220 which is slidably fitted within the tube 212. The needle housing 215 is identical to needle housing 15 of FIGS. 1-4 except that collar 55 comprises annular rim 255 at its distal end 56 and that needle housing 215 is provided with a gas permeable section 276 connecting chamber 75 to depression 66. As is known in the art, annular rim 255 is shaped such that distal end 56 forms a female Luer lock fitting which is connectable to male Luer lock fitting 210 of plastic syringe 200. Connecting chamber 75 to depression 66 via a gas permeable section 276 means that the user can control with their finger (by covering the end of the section 276) the outflow of air when filling the chamber 75 with an injectable fluid. Gas permeable section 276 could be replaced with a vent.

(43) FIG. 7D shows a needle housing 315 for connection with a plastic syringe 300 with a male Luer slip fitting 310 at its proximal end. The plastic syringe 300 comprises a cylindrical tube 312 and a plunger 320 which is slidably fitted within the tube 312. The needle housing 315 is identical to needle housing 15 of FIGS. 1-4 except that the internal cylindrical cavity at distal end 56 of collar 55 comprises a Luer taper 355 instead of a screw thread. As is known in the art, Luer taper 355 is shaped such that distal end 56 forms a female Luer slip fitting which is connectable to male Luer slip fitting 310 of plastic syringe 300.