Medical device with means protecting against inadvertent needle-stick

Abstract: A medical device includes a hollow needle 4 having a sharpened tip 6 for piercing the skin of a patient. Means 14 is provided for moving the needle relative to a housing 10 between a first ready-for-use position and a second retracted needle protected position. Resilient means is provided in the form of an arm 40 attached to the housing 10 said arm having a free end 44 which in the second retracted needle protected position of the needle 4 engages the needle flank to move said needle tip laterally.

Description: The present invention relates to medical devices and in particular, to medical devices such as intravenous catheters, which include a hollow needle having a sharp distal end or tip for piercing the skin of a patient. The existence of infectious diseases such as AIDS and hepatitis has highlighted the danger to which medical personnel may be exposed when treating patients by means of catheter devices where a sharp needle tip is used to pierce the skin of a patient. Medical personnel have been infected by physical contact with, or accidental prick by an infected needle (needle-stick). In order to protect medical personnel against inadvertent needle-stick, a number of solutions have been developed whereby a protective means incorporated within the catheter prevents physical contact with the needle after use and hence against inadvertent needle-stick. One known device for protecting the needle after use is described in US Patent 5447501. In this document, there is described an infusion catheter assembly including a hollow needle having a sharpened distal tip for piercing the skin of a patient. In a ready-for-use position the needle passes through a hole in a rigid front part which houses a resilient member. The resilient member is retained under tension by the needle flank and exerts a force substantially at right angles to the longitudinal direction of the needle. In its retracted position, that is, when the needle tip is moved back through and beyond the hole in the rigid front part the resilient member biases the needle tip laterally to prevent re-entry of the needle tip through the hole. This device is a relatively simple and economic device and is effective to minimise the danger of inadvertent needle stick. However, since the resilient member is under compression until the device is actually used and since the shelf life of the device is up to three years from manufacture, it has been found advisable to make the resilient member of coiled spring steel in order to avoid the permanent set of the resilient member which would thereby lose its resilience. A similar device is described in the French document FR-A-2 684 006. There it is disclosed an end piece for a puncture needle for a catheter, comprising a flexible sheath forming a compressible bellows. The sheath is arranged around the puncture needle and, after being extended, its length is at least equal to that of the puncture needle. When extending the sheath, the needle tip is retracted into the sheath. The distal end piece of the sheath comprises a resilient arm which is biasing the needle shaft laterally and which deflects the needle tip from the distal opening of the shaft, thus preventing the needle tip from passing through this opening again. The device described in FR-A-2 684 006 comprises all features of the preamble of claim 1. It is an aim of the present invention to provide a simple but effective means for protecting the point of a needle forming part of a medical device, which incorporates resilient means for deflecting a needle tip in a needle protected position but which avoids the necessity of using coiled spring steel. WO 95 19193 discloses an infusion catheter apparatus comprising an injection needle, means for moving the needle relative to a housing between a first ready-for-use position and a second retracted needle protected position, the housing including a front part with a through hole for the passage there through of the needle. The means for moving the needle is obliquely attached to the proximal needle end and, on the other hand, fits axially into the proximal part of the housing, when retracted into this part. This geometry results in a lateral tension on the needle shaft so that the needle tip is biased laterally when retracting the needle. GB-A 2 292 525 provides a catheter unit comprising a catheter, a needle, a catheter hub, a needle tip protector and a locking device. In the unlocked position, the locking device retains the catheter hub on the needle. On withdrawal of the needle by a needle hub, distal to the needle tip, through a slot the locking device pivots into a locked position, by virtue of the action of a leaf spring, releasing the catheter hub from the needle. Separation of the catheter from the needle therefore is only possible after the needle tip is shielded. The needle is restrained by a locking cam and preferably a tongue. There may also be provided gripping surfaces on the side walls of the needle protector and needle hub. According to the present invention, a medical device comprises a hollow needle having a sharpened distal tip for piercing the skin of a patient, a needle hub connected to the needle, a housing having a means for moving the needle relative to the housing between a first ready-for-use position where the needle tip is external of the housing and a second retracted needle protected position where the needle tip is within the housing, the housing including a front part formed with a through hole for the passage there through of the needle and resilient means which in the second retracted needle protected position of the needle engages the needle to prevent the needle passing through the hole, characterised in that the resilient means is in the form of a resilient arm attached to the housing, the resilient arm including a distal free end in engagement with the needle hub in the first position, and a proximal free end in engagement with the needle hub in the second retracted needle protected position of the needle to thereby force the distal end of the arm to engage the needle flank to move said needle tip laterally, thereby to prevent the needle tip entering the hole. Preferably, the resilient arm is made from plastics material. An embodiment of the invention will now be described, by way of example, reference being made to the Figures of the accompanying diagrammatic drawings in which:- Figure 1 is a side elevation of an infusion catheter assembly with its needle in a ready-for-penetration position; Figure 2 is a longitudinal cross-section through the catheter assembly of Figure 1; Figure 3 is a longitudinal cross-section similar to Figure 2 but illustrating the needle after use between its ready-for-use position and a needle protected position; Figure 4 is a cross-sectional similar to Figures 2 and 3 but showing the needle in its needle protected position and a cannula assembly separated from the remainder of the catheter assembly. As shown, an infusion catheter assembly 1 includes a needle assembly 2 comprising a hollow needle 4 having a sharpened distal tip 6, said needle 4 extending forwardly from a needle hub 8. The needle hub 8 is located for sliding movement within a housing 10 and includes a lug 12 supporting a gripper 14. The lug 12 extends through a slot 16 formed in the housing 10 in order that the gripper 14 can be engaged to reciprocate the needle hub 8 forwardly and rearwardly along the length of the housing 10. The needle hub 8 is hollow and is closed by a filter 18 which with the hub 8 defines a blood flashback chamber 20. The forward distal end of the housing 10 is effectively closed by a hub support member 24 connected thereto. However, the member 24 is formed with a through hole 25 to allow the passage therethrough of the needle 4. The forward face of the member 24 is formed with a forwardly extending boss 26 for supporting the proximal end of a cannula assembly 30. As is well known in the art, the cannula assembly 30 comprises a hollow cannula 32 attached to a cannula hub 34. According to the present invention attached to the housing 10 is a resilient arm of plastics material 40, the arm 40 has a proximal end 42 and a distal end 44. As illustrated the arm 40 is so shaped and mounted on the housing 10 that the ends 42, 44 tend to enter the interior of the housing 10. In the ready-for-use position as illustrated in Figures 1 and 2, the needle hub 8 is located at the forward end of the housing 10 such that the needle 4 extends through the hole 25 in the hub support member 24 and through the cannula assembly 30, so that the distal tip 6 of the needle 4 extends beyond the free distal end of the hollow cannula 32. In this position, the hub 8 engages the end 44 and thus causes the arm 40 to adopt the position as illustrated in Figure 2 with the proximal end 42 of the arm located within the interior of the housing 10. Once penetration of the patient's skin has been effected, the gripper 14 is engaged to move the needle hub 8 along and towards the proximal end of the housing 10, that is, towards the position illustrated in Figure 3. This movement of the needle hub 8 will cause the needle 4 to be withdrawn through the hollow cannula 32 and the cannula hub 34. The proximal end of the needle hub 8 will also engage the arm 40 adjacent its proximal end 42 thereby forcing the distal end 44 of the arm to engage the flank of the needle 4. This rearward movement of the needle hub 8 continues until it reaches the needle protected position as illustrated in Figure 4. In this position, the needle hub 8 will have caused the proximal end 42 of the arm 40 to move outwardly from the interior of the housing 10 and simultaneously cause the distal end 44 of the arm 40 to engage and move the needle laterally such that the needle tip 6 can no longer enter the through hole 25 in the hub support 24. In this position the cannula assembly 30 can then be removed from the hub support 24. A particular advantage of the embodiment described above is that the arm can be made of a resilient plastics material. Further, the distal end 44 of the arm will not initially apply any force to the needle 4 when starting the withdrawal of the needle through the cannula 32, the force on the needle 4 will only increase when the needle hub 8 is moved to the back of the housing 10 and the friction force will be a maximum just before the needle 4 reaches its needle protected position. This is important since the initial force of withdrawal of the needle 4 from the patient is very critical to the user, usually a nurse, and if it too high she will not get the right feel.

Claims: A medical device comprising a hollow needle 4 having a sharpened distal tip 6 for piercing the skin of a patient, a needle hub 8 connected to the needle 4, a housing 10 having a means 40 for moving the needle 4 relative to the housing 10 between a first ready-for-use position where the needle tip 6 is external of the housing 10 and a second retracted needle protected position where the needle tip 6 is within the housing 10, the housing 10 including a front part 24 formed with a through hole 25 for the passage therethrough of the needle 4 and resilient means which in the second retracted needle protected position of the needle 4 engages the needle 4 to prevent the needle 4 passing through the hole 25, characterised in that the resilient means is in the form of a resilient arm 40 attached to the housing 10, the resilient arm including a distal free end 44 in engagement with the needle hub 8 in the first position, and a proximal free end 42 in engagement with the needle hub in the second retracted needle protected position of the needle 4 to thereby force the distal end 44 of the arm 40 to engage the needle flank to move said needle tip 6 laterally, thereby to prevent the needle tip 6 entering the hole 25. A medical device as claimed in Claim 1, in which the resilient arm 40 is made from plastics material.

Inventors: OSTERLIND ROLAND J, OSTERLIND, ROLAND J.
Applicants: BOC GROUP PLC, THE BOC GROUP PLC
Application year: 1997
Main classification: A61M5
IPC codes: A61M25, A61M5