GB2407187A

GB2407187A - Apparatus for tracking a number of medical instrument sterility cycles

Info

Publication number: GB2407187A
Application number: GB0324339A
Authority: GB
Inventors: Paul Jonathan Ross
Original assignee: ROSS ELECTRO MEDICAL Ltd
Current assignee: ROSS ELECTRO MEDICAL Ltd
Priority date: 2003-10-17
Filing date: 2003-10-17
Publication date: 2005-04-20
Anticipated expiration: 2023-10-17
Also published as: GB0324339D0; GB2407187B

Abstract

Apparatus for tracking medical instrument sterility cycles has a single expandable member having a projecting pawl at one end and an index wheel (340) containing the expandable member, such that the projecting pawl engages inside teeth (390) of the index wheel. The expandable member expands substantially uniformly over its whole length when heat is applied above a threshold, thereby causing the projecting pawl to engage a subsequent tooth (390) on the index wheel during a heating cycle. In this manner, an apparatus is provided that is simple, inexpensive, and portable and does not require a bi-metallic element to count sterility cycles in a sterilisation process.

Description

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APPARATUS FOR TRACKING A NUMBER OF MEDICAL INSTRUMENT

STERILITY CYCLES

Field of the Invention

This invention relet-es to an apparatus for tracking medical instrument sterility cycles. The invention is applicable to, but not limited to, an inexpensive and portable apparatus for tracking medical instruments sterility cycles using an automatic incrementing tagging system.

Background of the Invention

Surgical instruments require sterilization before use.

Often, for cost reasons, it is advantageous if the surgical instrument, or at least parts of the surgical instrument, can be re-used. Thus, the surgical instruments, or parts thereof, require re-sterilization.

To re-sterilise, the surgical instruments they need to be heated up to a temperature over 120 deg.C using an autoclave.

Generally, such surgical instruments have a limited life due to usage and sterilization procedures. The Medical Devices Agency in the United Kingdom has recommended that the number of uses be monitored by a traceable method (safety notice SN ')315). It was found that accessories that had exceeded tile number of recommended sterilization cycles were more likely to fail during use than newer instruments.

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:e . ë - 2 - A known and simple mechanism for tracking a number of sterility cycles applied to a medical instrument is for a surgeon or a member of the hospital staff to use a tagging system or label and manually record each sterilization cycle. Such tagging mechanisms or labels are sold within the medical device market and require the use of, say, a ball-point pen or the like to pierce or indent a marker, or the surgeon or member of hospital staff to write on a label each time the device is sterilized.

One major problem with such a mechanism is that it requires a person to remember to mark the tag each time a device is steriliscd. Clearly, this is prone to human error and is therefore renowned within the medical community for being too risky when working with such sensitive and critical equipment. Furthermore, such manual systems require records to be kept, which uses up valuable resource and time.

An improvement over this basic concept is for a sterilization counting device to be used, which includes an automatic counter/indication mechanism to indicate a number of times that a medical instrument/device has been heated to (or beyond) a particular temperature. One such device is illustrated in International Patent Application - WO 99/60520 - filed by Ultimate Medical Ltd. Unfortunately, the Ultimate Medical heat cycle indication unit is designed specifically for coupling to tubing, for example the tubing associated with laryngeal mask equipment. The device is therefore complicated by requiring two fixing mechanisms at each end of the tubing, as illustrated in Figure 1 of WO 99/60520.

1 C . c c. :: c c: .: :. - c.e - 3 A further disadvantage with the Ultimate Medical heat cycle indication urn it is that it requires a bi-metallic ring, strip or spring. The bi-metallic nature of the ring, strip or spring enables it to deflect in one direction due to the different co-efficients of expansion of the materials selected and how they are bonded together. Also, there is a clear indication in this document that when plastic is used for both the ring and the teeth, the plastic is configured to have different thermal expansion coefficients and operate in a similar manner to the bi- metallic strip.

A second device is illustrated in European Patent Application - EP 0581400 Al - filed by Ethicon Inc. The proposed device is used for semidisposable surgical instruments. However, this device is also complex to manufacture and is therefore too expensive and totally unsuitable for use with a large number of surgical instruments and devices.

The construction is also complex, as it employs two clasping' components one for operation during a heating cycle and one for operation during a cooling cycle. Thus, the mechanism works by independently rotating two ends Off a cylindrical sleeve, in each half of the case. Notably, the Ethicon device is not a small, inexpensive and portable independent apparatus that can be attached to, or used in, any proposed surgical instrument application.

Furthermore, the Ethicon device is intended to be an integral part of a hard surgical instrument and has not ! ;- ce. :.'s:e.:. :. - 4 -

been designed to work as a 'stand alone' apparatus. The second embodiment in EP 0581400 Al uses a complex arrangement having two legs and an arcuate member, with a memory metal alloy spring used to provide a bias for the two legs to move a leaf spring in or out, thereby engaging teeth in a toothed ring. Such an arrangement is clearly unsuitable for attaching to inexpensive medical equipment, for example cables, where the cost of the arrangement will be significantly more than the cable or inexpensive device.

A third device is illustrated in US Patent 5,359,993 - assigned to Symbiosis Corporation. Notably, the Symbiosis patent describes a mechanism that also uses a bi-metallic spring to advance a sterilization counter cycle for endoscopic surgical instruments only. The device needs to be carefully dimensioned, to ensure that the spring expands a specified amount dependent upon the applied temperature. The spring needs to expand sufficiently to jails the next tooth of the ratchet. Also, the bi-metallic spring is located in the handle of the endoscopic surgical instrument, which adds significant complexity to the manufacture of the instrument. As the device is an integral part of the instrument handle, the mechanism is inflexible and is therefore not appropriate for any other use.

Thus, there current: By exists a need to provide an improved method and apparatus for tracking medical instruments sterility cycles where the aforementioned disadvantages may at least be alleviated.

Statement of Invention

A' :e::. .e '.e.e::e :e.. .. . The preferred embodiment of the present invention provides an apparatus for tracking medical instrument sterility cycles. the apparatus comprises a single expandable member having a projecting pawl at one end of the expandable member; and an index wheel containing the expandable member, such that the projecting pawl engages inside teeth of the index wheel. The expandable member expands substantially uniformly over its whole length when heat is applied above a threshold thereby causing the projecting paw] to engage a subsequent tooth on the index wheel.

In this manner, by provision of an expandable member, such as a single plastic spring coil, to track medical instrument sterility (heat) cycles, the known use of costly and complex bi-metallic elements to expand and/or contract at different temperatures is negated.

Preferably, the apparatus is configured to be portable for attaching to any of a number of medical instruments and cables in order to track medical instrument sterility cycles, for example using a cable tie for affixment to said article.

Advantageously, the index wheel comprises a single disc operably coupled to a numerical counter that is rotated to increment a numerical value indicated on the numerical counter.

Further aspects of the present invention are as defined in the dependent claims. .

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Brief Description of the Drawings

Exemplary embodiments of the present invention will now be described, with reference to the accompanying drawings, in which: FIG. 1 illustrates a number of views of an apparatus for tracking medical instruments sterility cycles, in accordance with the preferred embodiment of the present invention; FIG. 2 illustrates a top view and a side view of a coil spring within an apparatus for tracking medical instruments sterility cycles according to the preferred embodiment of the present invention) and FIG. 3 illustrates a top view, bottom view and a sectional view of a gear index wheel arrangement within an apparatus for tracking medical instruments sterility cycles according to the preferred embodiment of the present invention.

Description of Preferred Embodiments

Referring now to FIG. 1, a number of views of an outer case of an apparatus for tracking medical instruments sterility cycles are illustrated, in accordance with the preferred embodiment of the present invention. The apparatus, hereinafter referred to as a 'tag', comprises an outer case 110, with a hinge mechanism 130 separating a first portion 112 and a second portion 114. The second portion 114, genera-fly considered as the 'top' portion of the tag, comprises an index wheel 120, which is l ::: be:. . :.

7 e.e ee cee 7 positioned within the top portion 114. The first portion comprises a pawl mechanism 116. Preferably, a snap fit base, also linked by the hinge mechanism 130, securely closes the tag assembly.

The index wheel is part of an incrementing mechanism which indicates when the tag has been sterilised a number of times, thereby indicating end of use for the medical instrument/device that the tag is affixed to.

Preferably, the tag includes a pointer 124 that moves into alignment with, say, a white dot 122 on the index wheel when the tag has been sterilized a particular number of times.

FIG. 1 also illustrates a sectional view 140 through A-A, which clearly shows the hinging mechanism 130 of the outer case 110 with the index wheel 120 fitted in a substantially central position. FIG. 1 also illustrates a plan view 150 of the tag assembly when closed.

Thus, the tag according to the preferred embodiment of the present invention is of a construction that can be readily attached and removed from a medical instrument that requires sterilization. The 'tag' is preferably attached to a medical instrument or cable by use of a standard miniature nylon tie wrap. This provides secure attachment of the thing to the device/cable without slipping or providing excessive tightness or damage to the instrument/cable surface.

Referring now to FIG. 2, a top view 200 and a side view 210 of a coil spring 220 for use within the apparatus for tracking medical instrument sterility cycles is ::: ::e ce . he:.e . . - - 8 illustrated in accordance with the preferred embodiment of the present invention. The internal plastic coil spring 220 fits inside an index wheel, which in turn is located within the outer casing (see outer casing 110 of FIG.1). The internal plastic coil spring 220 preferably has a pivot point '60 that provides a rigid resistance for applying a force to the end of the coil spring 220.

Furthermore, the pivot point 260 allows the coil to be positioned easily within the outer casing 110 prior to placing the index wheel over the top during assembly.

In accordance with a preferred embodiment of the present invention, the end of the coil spring 220 has a projecting pawl 27() that engages the inside of the index wheel. The operation of the sterility cycle tracking mechanism is described in greater detail below with respect to FIG.3.

Referring now to FlG. 3, a top view 310, bottom view 320 and a sectional view 330 of a gear index wheel arrangement 340 is illustrated, in accordance with the preferred embodiment of the present invention. FIG. 3 shows the index wheel 340 with a numerical indication on its surface 380. Preferably, the index wheels projects through the outer case, when closed, to allow a user to monitor a number of sterility cycles that the tag has undergone. In the preferred embodiment of the present invention, fifty t:>eth are visible on both the inner circumference 390 and outer circumference 395 of the index wheel 340.

Each time the tag is heated to the prescribed temperature (e.g. 134 deg.C) ire the sterilization process, the spiral r j t se ce. _ 9 _

plastic spring coil expands and continues to engage with the inside teeth 3'iO of the index wheel.

The gear index wheel 340 is arranged around a central axis 370 by means of the spiral plastic spring coil held within its diameter. Successive engagement of the gear index wheel 340 by the spiral plastic spring coil causes the index wheel 120 to rotate a distance of exactly one tooth thereby incrementing the numerical indicator. This allows the mechanism to rotate the index wheel one tooth after each subsequent sterilising cycle, for example, until fifty cycles as indicated are reached. When fifty cycles have been roorded the tag is configured to stop incrementing the numerical counter. This indicates to the user that the medical device must be discarded and replaced.

Advantageously, the incrementing mechanism will stop when the total number of prescribed cycles is reached, thereby indicating end of use. Preferably, such an end of use indication is made easily visible by a user glancing at the tag to see that the pointer located on the top of the tag is in alignment with, say, a white dot on the index wheel 340.

When the assembly cools down to ambient temperatures a check pawl prevents the Index wheel from returning to its original position. In this regard, the outer teeth 395 are then engaged by the check pawl to prevent the index wheel moving back to its original position after it has advanced one tooth.

t l. ::: : c :. ace - 10 Notably, the check pawl on the design only engages the outer teeth thereby leaving the plastic spring free to operate solely on the inner teeth. Advantageously, this arrangement is very simple and has been design using a single moulded part.

The preferred embodiment of the present invention provides a means of tracking cumulative sterilising (termed 'autoclave') cycles, for example, on small medical devices by the use of a gear index wheel 340.

Notably, in operation, upon heating the spiral plastic spring coil during a sterilization process, the spiral plastic spring coil expands substantially uniformly over its whole length. Therefore, and advantageously, this method of advancing an index wheel requires no 'bimetallic' material. Furthermore, the spring coil is injection moulded from the same material as the outer case, in the same sequence, thereby keeping production and assembly costs to a minimum.

Although the invention is described with reference to a tag for a medical device, it is within the contemplation of the invention that the inventive concepts described herein apply equally to any limited use item that is sterilised by the use of an autoclave. Clearly, in the area of surgery and patient care, such a simple and effective device is very important. In particular, risk assessment has become of great importance in the medical

field when looking at fallible manual systems. The

aforementioned inexpensive and automatic tagging mechanism addresses Che need for improved risk assessment and is also capable of implementation on a large scale. ( e #

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In summary, the inventive concepts of the present

invention propose a tag assembly that is produced from a special grade of Acetal co-polymer plastic that is preferably self lubricating to allow trouble free operation during it, limited life of 50 cycles. The engineering plastic material used should be stable at the temperatures expected and yet still must have a sufficiently large co-efficient of expansion (say 2%) to produce a marked increase in length for the internal spring. The inventor of the present invention has found that higher temperature plastics are more stable, but generally expand much less at the required temperature.

Thus, the expansion co-efficient of this grade of plastic is important to maintain the correct amount of movement to increment the index wheel one tooth at a time.

Thus, in summary, the tag assembly of the preferred embodiment of the present invention is not constructed in accordance with known devices that use a bi-metallic material. The preferred tag assembly expands equally in both width and length to obtain deflection of its rotation mechanism. Hence, the shape and length of the expandable spiral spring coil are particularly important in order to ensure that when the device reaches the prescribed temperature, it will increment only one tooth width.

Advantageously, the inventive concepts of the present invention propose a more simplistic rotation mechanism that rotates a single flat disc, as compared to the mechanism used in known devices, which rotate two cylindrical parts.

::: .e I. .e:e r 12 It will be understood that the method and apparatus for tracking medical instrument sterility cycles, as described above, provide at least one or more of the following advantages: (i) Flexibility and portability in being attachable to a range of devices; (ii) The apparatus is sufficiently small enough to attach to any item, by any means, such as a nylon tie wrap; (iii) The device features no metal parts that could affect sensitive equipment such as MRI systems; (iv) Inexpensive, in that it is made out of a simple plastic material; (v) Provides improved reliability due to there being a single moving (rotating) part, i.e. the index wheel/disc; (vi) Ease of: manufacture by using a single moulded injection part;

(vii) Wider applicability for use with a range of

devices and cables; (viii) The incrementing mechanism is tamperproof as the index wheel is flush with the outer case and the plastic spring and check pawl, thereby preventing movement of the index wheel in either direction by the user; (ix) The incrementing mechanism is more reliable than known mechanisms; and (x) The incrementing mechanism will stop when the total number of prc scribed cycles is reached, thereby indicating end of use. Preferably, this is easily visible by glancing at the tag to see the pointer located on the top in alignment with, say, a white dot on the index wheel.

. : a: : . : e Whilst specific, and preferred, implementations of the present invention are described above, it is clear that one skilled in the art could readily apply further variations and modifications of such inventive concepts.

Thus, an apparatus For tracking medical instrument sterility cycles have been provided where the disadvantages associated with prior art methods and apparatus have been substantially alleviated.

Claims

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::e.:e e:. c. .e ' Clams 1. Apparatus for tracking medical instrument sterility cycles, wherein the apparatus comprises: a single expandable member (220) having a projecting pawl (21()) at one end; an index wheel containing the expandable member (220), such that the projecting pawl (270) engages inside teeth (390) of the index wheel; wherein the apparatus is characterized in that the expandable member (220) expands substantially uniformly over its whole length when heat is applied above a threshold thereby causing the projecting pawl (270) to engage a subsequent tooth (390) on the index wheel during a heating cycle.
2. Apparatus according to Claim 1, wherein the expandable member (220) is a non-metallic element.
3. Apparatus according to Claim 2, wherein the expandable member (,220) is a non-bi-metallic element.
4. Apparatus according to Claim 3, wherein the expandable member (,'20) is a plastic spring coil.
5. Apparatus according to any preceding Claim, wherein the apparatus is configured to be portable for use in tracking medical instrument sterility cycles of one of a selection cuff medical instruments.
6. Apparatus according to Claim 5, wherein the apparatus is conficred as attachable to a medical instrument, for example using a 'snap-fit' arrangement.

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7. Apparatus according to any preceding Claim, wherein the apparatus configuration comprises an outer case (110) having a hinge mechanism (130)
8. Apparatus according to any preceding Claim, wherein the index wheel comprises a single disc operably coupled to a numerical counter that is rotated to increment a numerical value indicated on the numerical counter.
9. Apparatus according to any preceding Claim, wherein heat is app.l.i.ed to the apparatus in a sterilization process.
10. Apparatus according to any preceding Claim, wherein the index wheel comprises a dual-staggered teeth arrangement such that outer teeth of the index wheel operably engage with a pawl mechanism (116) to prevent a backward rotation of the index wheel after a heating cycle.
11. Apparatus according to any preceding Claim, wherein one or more of the following features of the apparatus are formed in a single moulded part: a check pawl, inner teeth, outer teeth, plastic spring coil.
12. Apparatus for tracking medical instrument sterility cycles (2':', 50, 100), substantially as hereinbefore described with reference to, and/or as illustrated by, FIG. 1 or FIG. 2 or FIG. 3 of the accompanying drawings.