MXPA98002061A - Systems to test the sterilized - Google Patents

Abstract

A sterilizer evaluation apparatus (50), for use in the efficiency test in the air removal stage of a sterilization cycle within a sterilizer, includes a tube (29 of thermally insulating material, the orifice is closed in a end (52) and open in the other for the sterilizer inlet A plurality of thermally conductive masses (51) are placed around the tube (2) and thermally separated from one another by an air space (59), and a temperature detector in an inlet (61) in one of the masses adjacent to the closed end of the tube An outer cover (25) defines an air gap around the thermally conductive masses and thermally insulated the masses of the heat inside the sterilizer. the evaluation chamber is placed in a sterilizer, the penetration of sterilant along the orifice of the tube (2) during a sterilization cycle, is inhibited by the accumulation of a re and / or non-condensable gas within the hole resulting from the condensation of moisture on the walls of the orifice. By measuring the temperature inside a thermally conductive mass (51) adjacent to the closed end of the tube (2), the presence of sterilant can be detected in the region adjacent to the orifice of the tube.

Description

SYSTEMS TO TEST THE STERILIZERS The present invention relates to systems and methods for determining the effectiveness of sterilization cycles in sterilizers. A sterilization process used to sterilize medical and hospital equipment is only effective if a certain combination of environmental conditions is performed within the sterilizer chamber. For example, when steam is used as a sterilizer, the purpose of the sterilization process is to supply steam of a suitable quality, and at an appropriate temperature in contact with all the surfaces of the articles that are sterilized for a correct duration of time. In some steam sterilizers the sterilization processes are typically carried out in three main phases. In the first phase, air trapped inside the cargo that is processed is eliminated. The second phase is a sterilization stage, in which the load is subjected to steam under pressure from a REF .: 27008 recognized combination of time and temperature, which is known as sterilization effect. The third phase is a drying phase in which the condensate formed during the first two phases is eliminated when the chamber is evacuated. The removal of air from the sterilization chamber can be done by several methods. For example, in a steam sterilizer by gravity, the principle of gravity displacement is used, in which steam enters the top of the chamber by displacing air through a valve at the base of the chamber. In a pre-vacuum steam sterilizer, on the other hand, the air is removed due to the force by the evacuation in the deepest of the chamber or by a combination of evacuation and steam injection in either of the two subatmospheric pressures and / or superatmosferica. Any air that is not removed from the sterilization chamber during the air removal phase of the cycle or that leaks into the chamber during a subatmospheric pressure stage due to defective gaskets, valves or seals, air pockets can form inside the chamber. the load that is sterilized. Likewise, any non-condensable gas (which, in this context, means that the gases have a boiling point below the boiling point of the sterilant) which are present in the sterilization chamber or are entrained within the steam supplied to the sterilizer. Camera can form gas pockets inside the cargo. These air or gas pockets can create a barrier to steam penetration, thereby preventing the proper sterilization conditions that are carried out on all surfaces of the cargo. This is particularly true when porous materials such as hospital bedding or structures that are sterilized because air or gas pockets prohibit steam from penetrating the inner layers of such materials. As a result, sterilization can not occur. Therefore, there is a need that is capable of determining the effectiveness of the sterilization cycles and in particular, determining whether it has had sufficient steam penetration. Similarly, when using another sterilizer different from steam, there is a need for it to be able to determine that the sterilant has penetrated a load sufficiently for the sterilization to take place. A commonly-used method for evaluating the effectiveness of air removal during the phase of eliminating a steam sterilization cycle from a porous load and / or for testing the presence of non-condensable gases is known as the Bowie-Dick test. The typical Bowie-Dick test pack essentially consists of a stack of washed towels folded to a specific size, with a chemical indicator sheet placed in the center of the pack. The chemical indicator test sheets experience a visible change from one color to another, for example, from an initial white color to a final black color, exposed to the sterilization process. If the elimination of air inside the sterilizer is sufficient, or if non-condensable gases are present during the process in sufficient quantity, a gas / air bag can be formed in the center of the package by means of this preventing the steam from coming into contact with the sheet of the chemical indicator sensitive to steam. The consequence of inadequate vapor penetration is the development of a non-uniform color across the surface of the chemical indicator test sheet: thus, the presence of an air / gas bag can be recorded as the indicator failure to suffer a complete or uniform color change indicative of adequate vapor penetration. Biological indicators can also be used to provide information on the sufficiency of a sterilization cycle. Biological indicator test systems typically employ live spores that are attached to a sterilization cycle. After the cycle, the spores are incubated and the system detects if there is any growth. If there is no growth, this indicates that the sterilization process has been effective. Thus, the biological indicators can indicate if the conditions were present, but the length of time to obtain results due to the incubation period frequently at least 24 hours. Therefore, biological indicator systems are frequently used in conjunction with chemical indicators because the color change of the chemical indicators provide an instantaneous result. In addition, by using both chemical and biological indicators, both provide information on the sufficiency of the air removal stage and the sterilization stage. Parametric monitoring has also been used to monitor or control a sterilization cycle to ensure that the proper sterilization conditions are met. For example, in US Patent No. 4,865,814 by Childress, an automatic sterilizer is disclosed, which includes a microprocessor that monitors both temperature and pressure levels within the sterilization chamber and controls a heater to allow both the temperature and pressure increase to predetermined levels before starting a counter. Once the counter is started, it stops if the pressure or temperature levels fall below a predetermined minimum. Since it is known that the pressure and temperature variables of the saturated vapor are dependent variables when the saturated vapor is enclosed in a sealed chamber, monitoring these two variables can ensure that the appropriate conditions are maintained during the sterilization cycle. Although it is desirable to monitor environmental conditions within the same sterilization chamber, it is generally considered more desirable to be able to monitor environmental conditions within a current load that is sterilized or within a test package (such as the test package). Bowie-Dick) that such represents a burden. Although the Bowie-Dick test package is generally recognized as suitable for use in determining the effectiveness of the air removal stage of pre-vacuum sterilizers, it still has several disadvantages. Since the test package is not preassembled, it must be constructed each time the procedure is used to monitor the development of the sterilizer. The preparation, assembly and use of the towel package is time consuming and it is uncomfortable, in addition, to vary the factors, such as washing, pre-humidification, thickness and use of the towels, and the number of used towels, alters the results of the test . Therefore, alternative Bowie-Dick test packages have been developed to overcome these limitations. An example of an alternative Bowie-Dick test package for a gas or steam sterilizer is described in EP-A-0419282. This test package includes a container that has walls at the top and bottom with a porous packer material placed inside the container. The packer material tests the penetration of the sterilant by providing a path that acts to prevent the flow of the sterilant through the test pack. A removable lid seals the bottom end of the container, while a hole in the upper wall of the container allows the descending steam to enter the packing material inside the container. The test package includes a chemical indicator to detect the penetration of sterilant. If the sterilant penetrates the packer material of the test pack, the chemical indicator sheet may undergo a complete color change. If the sterilant does not sufficiently penetrate the packing material, the chemical indicator undergoes a complete color change, thereby indicating inadequate air removal or the presence of non-condensable gas, or in other words, a failure of the Bowie test. Dick. Other test packages for use in gas or steam sterilizers are described in EP-A-0421760; US-A-5 066 464; WO 93/21964 and US-A-5 270 217. In each of these test packs, the sterilants in the sterilization chamber must pass through some form of physical barrier, before reaching a sterilizer detector within the test package. . WO 93/21964, for example, describes a test unit comprising a test cavity having an opening at one end to allow the entry of gases from the environment, a temperature detector at the other end and a heat absorber ( for example, gauze, felt, a polymer foam with open cells) between the temperature detector and the opening. US-A-4 594 223 describes several apparatuses for indicating the presence of non-condensable gas inside the sterilization chamber. In one version, the heat and humidity detectors are placed at the smaller end of the elongated cavity that opens at the upper end. The heat absorbing material in the form of fibrous insulating material is placed inside the cavity between the opening and the detector. In another version, the path between the opening and the detector is through a heat-absorbing block in the form of an aluminum mass surrounded by insulation, instead of a fibrous heat-absorbing material. US-A-4 115 068 discloses an air indicating apparatus for use in sterilizers, comprising a vertical tube that is open at its lower end and closed at its upper end. The tube is made of heat insulating material. Lined on its inner surface with a heat conducting material. A thermal indicator strip extends axially within the tube. Another known arrangement for testing the penetration of the sterilant into a particular location within a test package comprising a very long stainless steel tube (typically 1.5m) with a narrow orifice (typically 2.0mm) that provides the only access for the sterilizer to the predetermined place. The problem of the present invention is to provide, to the sterilizer test systems, an apparatus for evaluating the sterilizer which is of comparatively simple construction which can reliably operate to allow the ineffective sterilization cycles to be identified.

The present invention provides an apparatus for evaluating the sterilant that is used in a sterilizer to determine the efficiency of the air removal stage of a sterilization cycle, the apparatus comprises a chamber defining an unoccupied space; an opening for the entrance of the sterilizer in the unoccupied space; a heat absorbing part which, when the apparatus is in use in a sterilizer, preferably receives color from the vacated space; and it is intended to fix a detector to detect the presence of sterilant at a predetermined location within the vacant space remote from said opening, the walls of the chamber consist of a thermal insulating material that prevents the transmission of heat from inside the sterilizer to the unoccupied space through the walls of the chamber through this the penetration of the sterilant from said opening to said predetermined location during a sterilization cycle is inhibited by the accumulation of air and / or non-condensable gas within the resulting vacant space of condensation of moisture on the walls of the chamber. The apparatus may be provided with a detector for detecting the presence of sterilant at a predetermined location. The detector can be composed of a temperature detector to detect the temperature at the predetermined place. Alternatively, or the detector may also be comprised of a chemical / biological detector to detect the presence of sterilant at the predetermined location. The heat-absorbing part may be surrounded by a part of thermal insulation, therefore, during the sterilization cycle, the heat-absorbing part may preferably receive heat from the unoccupied space. The chamber can be composed of a passage that is closed at one end, the predetermined place that is towards the closed end of the passage, and the opening for the entrance of the sterilizer that is at the other end of the passage. The passage may have the hole in a tube of thermally insulating material and the heat absorbing part may be composed of a plurality of conductive masses thermally placed around the tube along it, the masses being thermally separated from one another. Alternatively, the passage may be formed in a mass of thermally insulating material; in this case, an internal part of the mass of insulating material forms the heat absorbing part of the apparatus and an outer part functions as the thermally insulating part thereby, during a sterilization cycle, the heat absorbing part can receive the heat preferably of unoccupied space. Alternatively, the passage may comprise a plurality of interconnected compartments. In the latter case, the compartments can be arranged linearly, the opening of the sterilizer inlet that is in the compartment at one end of the linear array, and the predetermined location that is in the compartment at the other end of the linear array. Alternatively, the compartments can be arranged so that one, at least, of the compartments is surrounded by others, the opening for the entrance of the sterilizer is inside a compartment at the periphery of the arrangement, and the predetermined place is in a compartment in the center of the arrangement. A heat absorbing part of the apparatus may comprise heat absorbing masses within the compartment. The present invention also provides an apparatus for evaluating the sterilant for use in a sterilizer to determine the efficiency of the air removal stage of a sterilization cycle, the apparatus is composed of a tube of thermally insulating material, the orifice of the tube defines an unoccupied space which is open at one end for the entrance of the insulator and is closed on the other side; a plurality of conductive masses thermally placed around the tube, along the length thereof, the masses are thermally separated one from the other; and the thermal insulation around the tube and the thermally conductive masses thereby the penetration of the sterilant along the orifice of the tube during a sterilization cycle is inhibited during the accumulation of air and / or non-condensable gas within the unoccupied space resulting from the condensation of moisture on the walls of the orifice, the apparatus also comprises fixing a detector for detecting the presence of sterilant at or adjacent to the closed end of the tube. The apparatus can be used in combination with a second detector placed to detect the temperature in a sterilization chamber where the apparatus is placed.

DESCRIPTION OF THE DRAWINGS. By means of the examples only, the embodiments of the invention can now be described with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of the evaluation apparatus of the sterilant according to the invention; Fig. 2 shows a longitudinal section of the apparatus of Fig. 1; Figs. 3 to 6 show diagrams of the cross sections of other evaluation apparatuses according to the invention; Figs. 7 through 9 show diagrams of the cross sections of test packages incorporating evaluation apparatuses according to the invention; Fig. 10 is a perspective view, of the section of a removed part, of another evaluation apparatus of the sterilant according to the invention; Fig. 11 is a perspective view, of the schematic part, of a component of the apparatus of Fig. 10; and Fig. 12 is a view similar to Fig. 11 but the part a cross section.

DETAILED DESCRIPTION OF THE INVENTION Figs. 1 and 2 show an evaluation apparatus of the sterilant 1 suitable for use in a system for testing the effectiveness of a sterilization cycle in a steam sterilizer or a low temperature gas sterilizer in which the sterilization is performed using an agent microbiological in the presence of moisture. The apparatus 1 is intended to be located in the sterilizer chamber to provide an evaluation along the path of the sterilizer (e.g., steam) from within the chamber may pass before it is detected by the detector at a predetermined location within the apparatus . If the presence of the sterilant is not detected by the detector during a sterilization cycle (indicates that the conditions within the sterilization chamber the sterilizer has not been able to penetrate the evaluation route), the sterilization cycle is judged to be ineffective . The evaluation apparatus 1 is generally cylindrical and is composed of a tube 2, with a hole 3 of generally constant cross section, which is closed at one end 4 and open at the other end 5. The wall 6 of the tube 2, which is relatively thick, is formed of a thermally insulating material and has a relatively high heat capacity. A sterilizer detector 7 of any suitable type is placed on the closed end 4 of the tube.

In use, the evaluation apparatus 1 is placed in the sterilization chamber of a sterilant connected to the hole 3, through the open end 5, with the environment inside the sterilization chamber. The apparatus is used in the orientation shown in the drawings, for example, with the open end 5 of the hole 3 directed downward, so that any condensate that forms inside the hole can drain out. Depending on the thermal properties of the tube 2, it has been found that a noncondensable air or gas bag may tend to remain at the closed end 4 of the hole 3 during an inadequate sterilization cycle and may inhibit the entry of the sterilant. Accordingly, an appropriate selection of the properties of the tube can be arranged so that the sterilant can not penetrate the end of the orifice when the environmental conditions in the sterilization chamber do not meet the requirements for effective sterilization. The detection of the sterilant by the detector 7 is then an indication that the sterilization cycle has been effective in which no detection is an indication that a sterilization cycle has failed to meet the requirements. In general, the thermal properties of the tube 2 must be such that the heat and humidity of the sterilization chamber can pass the detector 7 through the hole 3 instead of through the walls 6 of the tube (with the result, in In the case of a steam sterilizer, the steam that passes inside the hole 3 may tend to condense on the walls of the hole and does not immediately penetrate the detector). In the case of the apparatus shown in Fig. 1, it can not be noted that the internal surface of the wall 6 of the hole 3 is composed, like the rest of the apparatus, of a thermal insulating material. Furthermore, if the wall of the hole is sufficiently thick, the internal part of the mass of the thermally insulating material can function as a heat absorbing part which, in use, can preferably receive heat from the hole 3 because it is surrounded by an outer part of the material thermally insulating which prevents the transfer of heat from the sterilizer through the wall of the orifice in a transverse direction. It may be noted that the apparatus 1 does not require the presence of any form of packing material, or other physical barrier, within the hole 3 to inhibit the penetration of the sterilant to the detector 7. The tube is also comparatively short (typically, with a length of the hole less than 30 cm, preferably less than 20 cm, and more preferably less than 10 cm) and, therefore, does not depend on the length to prevent penetration of the sterilant to the detector 7. Indeed, it has been found that a An appliance with a hole length of 7.5 cm can provide an indication of the effectiveness of a sterilization cycle. The hole 3 functions as a closed chamber composed of an unoccupied space that separates the detector 7 from the opening 5 and, as described above, it is the thermal properties of the surrounding walls 6 which cause the penetration of the sterilant into the chamber for which is inhibited and thus allow the apparatus 1 to be used to indicate the effectiveness of a sterilization cycle. Suitable materials for walls 6 of tube 2 include polysulfone, polyphenylsulfone, polytetrafluoroethylene and polyetheretherketone. In general, it is believed that materials for which the ratio of heat capacity to thermal conductivity is within the range from 1x10 to 12 x 10 sec./m (more particularly from 4 x 10 to 11 x 10 sec./m The outer diameter of the tube 2 is determined by the thickness of the walls 6 and the diameter of the hole 3, and is advantageously as small as is consistently possible with the tube having the required thermal properties. of the hole 3 is also advantageously as small as possible but not so small that it can be blocked by the condensate that forms inside the orifice during the sterilization cycle.It has been found that an indication of the effectiveness of a sterilization cycle it can be obtained with apparatuses in which the outer diameter of the tube 2 is 5 cm or smaller and in which the diameter of the hole 3 is 0.9 cm or smaller (preferably 0.6 cm). However, it may be appropriate for the hole 3 to include means such as screens for modifying the air flow in the orifice, for example to reduce turbulence. Any means must be selected to ensure that the unoccupied space separating the detector 7 from the opening of the hole 5 is retained and not so narrow that it can be blocked by the condensate during a sterilization cycle. The detector 7 can be a chemical indicator that changes color in the presence of sterilant; or a biological indicator; or a detector that detects a parameter of the environment (for example, temperature or humidity). If required, several detectors can be used. For example, a chemical indicator may be used in combination with a biological indicator, or detectors may be used to detect various parameters of the environment (eg, temperature, humidity and pressure). Fig. 7 illustrates a use of a test apparatus of the type shown in Figs. 1 and 2. Fig. 7 shows a cross-sectional view of a self-contained electronic test pack 10 that can be placed in a sterilization chamber to determine the effectiveness of a sterilization cycle. As described below, the test pack 10 operates, during a sterilization cycle, to measure the temperature in two places, one is inside the evaluation apparatus 1 and the other is at a reference point within the same sterilization chamber . These temperature measurements are then used to determine whether or not the sterilization cycle, in particular the air removal phase of the cycle, was effective (for example meet certain prescribed requirements). In the test pack shown in Fig. 7, the end of the wall 4 of the test apparatus is hollowed out to form a container 11 containing the electronic components of the test unit. These components are described below. The electronic component container 11 has a lid at the end 12 and is placed inside an outer container 13 to be secured, for example with screws. When secured, the outer container 13 holds the end cap 12 towards the electronic component container 11 for sealing purposes. The outer container 13 is constructed of a rigid structural material, such that when subjected to an effort, it returns to its original shape. For example, any type of metal, as well as fiberglass or carbon fiber reinforced plastic with softening temperatures greater than 150 ° C. they can be used for the outer container 13. The components contained within the electronic component container 11 can be protected from extreme heat within the sterilization chamber by a vacuum within the container. For this end, the electronic component container 11 consists of a one-way valve 14 that opens when the external pressure of the container 11 drops below a predetermined value. Then, when a vacuum is created within a sterilization chamber with a test pack 10 placed inside, the valve 14 opens to allow a vacuum to also form inside the container of electronic components 11. The container of electronic components 11 which it contains the detector 7 of the evaluation apparatus 1, (in this case a temperature detector), together with a second temperature sensor 15. The temperature detectors 7 and 15 can be of any suitable type of temperature transducer, for example thermocouples or thermotransmitters. The temperature sensor 7, as already described, is positioned such that it measures the temperature at the end of the hole 3 of the evaluation apparatus 1. The temperature sensor 15, on the other hand, measures the external temperature. Thus, when the electronic test pack 10 is placed inside a sterilization chamber, the temperature sensor 15 measures the temperature of the chamber.

The container 11 also contains a circuit board 16, mounted so that it is thermally insulated from the walls of the container to prevent conduction of external heat to the electronic components mounted on the tablet, including a microprocessor and a memory, preferably a memory only electrically erasable programmable reading (EEPROM). The plates mounted on the surface 17, batteries 18, the temperature detectors 7 and 15, a light emitting diode 19 and a pressure sensor 20 are all electrically connected to the board of the circuit 16. As the temperature detectors 7 and 15 They measure the temperatures, the read temperatures are stored in the memory of the test package together with the microprocessor data. Once the microprocessor determines that a sterilization cycle is complete, it then determines (from the stored temperature readings) whether the sterilization cycle is satisfactory, in other words, that the sterilizer has adequately penetrated the length of the hole 3 in the sterilization cycle. evaluation device. If the microprocessor determines that the sterilization cycle was successful, the light emitting diode (LED) 19 emits a light. In a completely self-contained electronic test package, only a simple LED is necessary to indicate whether the cycle has passed. With a simple LED, the LED can turn on continuously to indicate a cycle step and can flash to indicate a fault in the cycle. Alternatively, two LEDs can also be used, to indicate a cycle step and cycle failure respectively. If the sterilization cycle has passed, an LED emits a green light. If the microprocessor determines that the sterilization cycle has failed, the other LED emits a red light. In some situations, this is desirable to transfer the data stored in the unit's memory to an external processor or memory or printer. The data transfer can be initiated by activating a magnetically activated switch (not shown), preferably a reed switch. The manner in which the test pack 10 determines the effectiveness of a sterilization cycle is, briefly as follows. As already described with reference to Figure 1, the thermal properties of the evaluation apparatus 1 are such that, during the air removal phase of a sterilization cycle, an air bag may tend to remain indoors (closed) from the end of the hole 3. Similarly, non-condensable gases are entrained by the vapor and may also tend to remain inside the end of the orifice 3. The size of the air / gas bag is indicative of the efficiency of the sterilization cycle; larger when the air removal phase of the cycle is less suitable. The air / gas bag prevents the detector 7 from being exposed to all the effects of the sterilant, thus there is an increase in the difference between the temperature of the detector 7 and the temperature of the detector 15. The test pack 10 determines whether this difference of temperatures exceeds a predetermined value at a predetermined point within the sterilization cycle and, if so, the cycle is judged to be unsatisfactory. This predetermined difference is determined by verifying experiments where the development of the electronic test packages is compared with a standard Bowie-Dick textile test package in accordance with European or National standards, recognized Internationally. For example, the test package must be pre-programmed so that, if the temperature difference is greater than 2 ° C. in a period of 2 minutes to 40 seconds after the temperature of the chamber reaches a subject temperature of sterilization of 134 ° C, the cycle is considered unsatisfactory. In addition, the temperature in the chamber can remain above a suitable temperature sterilization temperature for the sterilization to occur. Although the examination of the difference in temperature between the external temperature and the internal temperature (as described) provides direct information on the penetration of heat into the detector 8 placed inside the evaluation apparatus 1, this does not directly reveal the penetration of the sterilant to the detector. By interference, the rapid equilibrium between the sensitive spot within the evaluation apparatus and the sterilization chamber indicates the absence of an air / gas bag. In the case of a steam sterilizer, it is therefore possible to directly measure the penetration of moisture into the sensitive point within the evaluation apparatus. Towards the end, a humidity detector, such as a conductivity detector or a relative humidity detector, can be used instead or also the temperature sensor 8 to determine the proper moisture penetration at the sensitive point within the evaluation apparatus. and therefore, by inference, the vapor. The temperature sensor 15 that measures the temperature in the sterilization chamber remains the same. Fig. 3 shows an alternative of the test apparatus, similar to that shown in Figs. 1 and 2 except that the section of the cross section of the hole 3 decreases downward from the detector 7: Fig. 4 shows an evaluation apparatus 24 in which the wall 6 of the hole 3, (however still formed of a thermally insulating material) is thinner than in Figs. 1 and 2, with additional thermal insulation is provided to trap the air between the wall 6 and an outer cover surrounding 25. The outer cover 25 needs not to be formed of a thermally insulating material and can, for example, be made of metal. The outer cover 25 is formed in two parts, one of these (21) is secured and sealed to a flange 22 around the mouth of the hole 3. The second part 23 of the cover 20 is a cap on the end and is screwed to the first part so that it can be removed to give access to the detector 7 at the closed end of the hole 3. The interface between the two parts 21, 23 of the cover 20 is also sealed. In the evaluation apparatus in Fig. 4, the space 26 between the wall 6 and the outer cover 20 may contain some form of the thermally insulating filler material, for example a thermally insulating foamed material or glass wool. Alternatively, the space can be evacuated. The construction illustrated in Fig. 4 allows a combination of different materials to be used and made it possible to provide an evaluation apparatus having the same thermal properties as the apparatus shown in Fig. 1 but with smaller external dimensions. In this construction, the wall 6 of the orifice constitutes a heat absorbing part of the apparatus which, by virtue of the surrounding air space 26, can receive heat preferably from the orifice 3 where the apparatus is placed in a sterilizer. Figs 8 and 9 illustrate the uses of an evaluation apparatus of the type shown in Fig. 4. Fig. 8 illustrates a test pack 30 which is formed by providing the evaluation apparatus 24 of Fig. 4 with a cover 31 supporting a biological indicator 32 so that when the lid 31 is fixed on the evaluation apparatus, on the opening of the end of the hole 3, the indicator 32 is placed on the closed end of the hole. The indicator 32 can be any suitable indicator, for example an indicator available under the designation of the name "ATTEST" by Minnesota Mining and Manufacturing Company of St. Paul, Minnesota, USA Cap 31 has openings 33 that allow the sterilant to enter hole 3 from outside of test pack 30. Test pack 30 is attempted to be placed in a sterilization chamber at the start of a sterilization cycle. and that is eliminated when the cycle has been completed. The indicator 32 is then removed from the evaluation apparatus and subjected to the prescribed treatment to enable it to show whether or not the sterilization cycle was effective. The evaluation apparatus can then, of course, be adjusted with a replacement indicator 32 and used again. Fig. 9 illustrates a test pack 35 that is similar to that shown in Fig. 8 except that it is provided with a chemical, rather than an indicator, biological. The indicator is shown in the form of a strip 36 (this is composed of a substrate that transports a sensitive ink to the sterilant) that extends along the hole 3. A suitable chemical indicator is supplied under the trade designation "Comply 1250" by Minnesota Mining and Manufacturing Company of St. Paul, Minnesota, E. U .. Test pack 35 is also attempted to be placed in a sterilization chamber at the start of the sterilization cycle and removed when the cycle is complete. The indicator strip 36 is then removed from the evaluation apparatus and an examination of the color change that has occurred along the length of the strip can immediately show that both sterilant has penetrated along the hole 3, and whether or not the Sterilization cycle was effective. The evaluation apparatus can then, of course, be adjusted with a replacement indicator strip 36 and used again.

Fig. 5 shows another evaluation apparatus, similar to that shown in Fig. 4 but incorporating a plurality of detectors instead of just one detector. Fig. 5 shows four detectors 40, but any appropriate number can be used. The detectors 40 are placed in different results along the hole 3, with one at the closed end of the hole and corresponding to the detector 7 in Fig. 2. The parameters detected by the detectors 40 during a sterilization cycle can indicating that both sterilizer has penetrated along the orifice 3 of the evaluation apparatus at various times during the cycle and, further indicates whether or not the sterilization cycle has been effective, a record of the sterilization operation can be provided. In each of the evaluation apparatuses shown in Figs. 1 to 5, the walls of the hole 3 are straight and uninterrupted but this is not essential. The hole 3 can, for example, follow a curved path provided that returns adjacent in the path are thermally insulated from each other. Such an arrangement must be capable of reducing the overall length of the evaluation apparatus. As another alternative, a series of constrictions can be formed along the orifice providing that none of these constrictions can be blocked by the condensate during the sterilization cycle, and provide that they can not eliminate the unoccupied space separating the detector 7 from the orifice. opening 5. An example of the evaluation apparatus of this type is illustrated in Fig. 6. The evaluation equipment 45 shown in Fig. is generally similar to that shown in Fig. 4 except for several walls with openings 46 in results along the orifice 3, which effectively divides the orifice in a series of communicating compartments 47. The compartments at one end of the hole 3 incorporate the inlet 5 through which the sterilant can enter the evaluation apparatus, and the compartment at the other end of the hole 3 incorporates the detector 7. Additional temperature detectors can be provided, in any, in the same compartment or or in one or more of the other compartments 47, as required. The evaluation apparatus shown in Fig. 6 can operate in a manner similar to that shown in Figs. 1 to 5 but can provide different operating characteristics. As an alternative to the linear arrangement of the components 47, shown in FIG. 6, the compartments can be arranged one inside the other, with the inlet 5 of the sterilant placed in a compartment in the center of the array. Each of the compartments can be individually thermally insulated so that the heat transfer from the opening 5 to the detector is through the unoccupied space in the compartments instead of the walls of the components. In each of the evaluation apparatuses shown in Figs. 1 to 6, the required thermal properties of the internal or chamber 3 provided by the walls of a simple insulating material. It may, in any way, be possible to provide equivalent thermal properties with walls with building compounds, which may include thermally conductive materials as well as thermally insulating materials. For example, an evaluation apparatus of the type shown in Fig. 1 and 2 may have one or more parts formed of a material having relatively high thermal conductivity in combination with the thermally insulating material to provide the required thermal properties. When the material having relatively high thermal conductivity is present, care must be taken to ensure that it does not cause any substantial increase in heat transfer in the longitudinal direction along the walls of the orifice 3. Alternatively, in the case of a evaluation apparatus of the type shown in Fig. 6, it may be possible to achieve the thermal properties required through the use of a thermally insulating material for the walls of the compartments 47 in combination with heat absorbers (masses with a high thermal capacity) inside the compartments, provide that the unoccupied space separating the detector 7 from the opening hole 5 is conserved and does not become narrower than it is blocked by condensate during a sterilization cycle. Fig. 10 illustrates an evaluation apparatus 50 which is generally similar to the apparatus 19 shown in Fig. 4 except that the thermally insulating wall of the tube 2 is surrounded by a plurality of thermally conductive blocks 51 placed from one side to the other as shown in FIG. length of the tube. As in Fig. 4, the evaluation apparatus 50 is provided with a surrounding outer cover 25 which is shown, in Fig. 10, to be opened at the end but, in use, is provided with a plate on the end. end corresponding to the end cap 23 of Fig. 4 to provide a hermetic seal. Only the closed end 52 of the tube 2 is visible in Fig. 10. The access to the hole 3 inside the tube 2 is provided through a plate at the end 53 that surrounds the opening at the end of the tube and supports both the blocks thermally conductive 51 and the outer cover 25. A thermally insulated optional cylinder 64 of foam material with open cells can be placed around the thermally conductive blocks 51, inside the outer cover 25.

The construction of the apparatus 50 (in particular the construction of the tube 2 and the blocks 51) may not be described in great detail with reference to Figs. 11 and 12 showing only a part of the apparatus, towards the closed end of the tube 2. The block 51 immediately adjacent the closed end 52 of the tube 2 is shown removed in Fig. 11 and has been omitted completely from Fig. 12. The orifice 3 of the tube 2 (visible in Fig. 12) of the circular cutting section but the outer cross section of the tube, except immediately adjacent the closed end 52, is square. The thermally conductive blocks 51, which form a part of heat absorber of the apparatus, are placed on the square section of the tube 2, each block being formed by two halves 54 having flat inner surfaces 55 corresponding to two of the outer sides of the tube. When in position on the tube 2, the two halves 54 of each block are held together by two elastic fasteners 56 which employ a recess 57 in the outer surfaces of the block. The square outer shape of the tube 2 and the corresponding shape of the interior of the blocks 51 provide good thermal contact between the tube and the blocks and the elastic fasteners 56 ensuring that the good thermal contact is maintained even accommodating the differences of the contraction expansion velocities of the tube and the blocks when the evaluation apparatus 50 is in use inside a sterilization chamber.

Although the blocks 51 are placed side to side of the length of the tube 2, they have no contact with another but are spaced insignificantly by thermally insulated rings-0 (one of these is visible in Fig. 11 and 12) placed between adjacent blocks. The resulting air spaces between the blocks cause the blocks to be thermally separated from each other and prevent heat from being transmitted through the blocks along the length of the tube 2. When all the blocks 51 are in position on the tube 2, these are secured in place by a circular fastener 60 (Fig. 10) fixed on the end of the tube adjacent to the end of the block. The penultimate block 51 in the tube 2 is formed with a circular opening 61 in which a temperature sensor, preferably a platinum resistance thermometer (PRT), is placed when the evaluation apparatus 50 is in use. The electric cables 62 of the temperature sensor 7 of the evaluation apparatus 19 of Fig. 4 and, different from the temperature sensor, are not placed in the hole 3 of the tube 2 but in one of the thermally conductive blocks 51 surrounding the tube adjacent to the closed end of this. Other forms of temperature detectors can, of course, be used. The evaluation apparatus 50 can be used in a test pack to determine the effectiveness of a sterilization cycle in the same manner as any of the apparatuses described above. In particular, the evaluation apparatus 50 can be used in a test package of the type illustrated in Fig. 7 and the evaluation apparatus is further comprised of a second detector arranged to measure the outside temperature of the test pack (for example in a sterilization chamber in which the test pack is placed when in use), and the electronic circuit of the test pack which, based on the measurements of the temperature detectors, functions in the manner already described with reference to the Fig. 7 to determine if a sterilization cycle is satisfactory. With a view for use in a test pack, the evaluation apparatus 50 is already provided with a second temperature sensor for measuring the outside temperature of the test pack and the electrical wires 63 of this second temperature sensor can be seen in FIG. 10, which extends into the space between the outer cover 25 and the thermally conductive blocks 51. During a sterilization cycle., the sterilant can enter the orifice 3 of the evaluation apparatus 50 only through the lower end (opening) of the tube 2. Because the tube 2 is thermally insulated from the heat in the sterilization chamber by a space with air inside the cover 2 (and by the thermally insulated cylinder 64 when presented), and because the walls 6 of the hole 3 are formed by thermally insulating material, the hole 3 can receive mainly heat from the sterilant entering the orifice. As a result, the temperature of the walls 6 can remain below the temperature of the sterilization chamber and the sterilizer can enter the orifice can condense on the walls 6 and not penetrate immediately into the end of the hole 3, which results in an accumulation of air or non-condensable gas inside the hole. The evaluation apparatus 50, like other evaluation apparatuses described above, is used in the orientation shown in the drawing for example with the opening at the end of the hole directed downwards so that any condensate that forms inside the orifice during A sterilization cycle can be drained off. The non-condensable air or gas bag that is formed within the hole 3 can inhibit the penetration of the sterilant to the end of the orifice and can influence the temperature at the closed end of the tube 2 and the surrounding thermally conductive blocks 51. In this respect , it can be noted that the blocks 51 are protected to avoid transmitting heat from one to another by the presence of air spaces 59. Accordingly, by measuring the temperature inside the blocks 51 at the closed end of the tube 2 in relation to the temperature inside the sterilization chamber, this can be determined if the sterilant has penetrated the end of the tube (indicates that the sterilization cycle has been effective) or if a bag of air or non-condensable gas remains at the end of the tube (indicates that the sterilization cycle has not been effective). The thermally insulated material from which the tube 2 is formed must enclose the vapor well, and be stable under conditions found in a sterilization chamber. Preferably, the thermally insulating material is a Liquid Polymer Crystal (LPC), more preferably a complete aromatic copolyester with 25% by weight graphite content. The thermally conductive material of which the blocks 51 are formed is preferably aluminum. The rings-0 58 between the blocks may be formed of rubber and the outer cover 25 of the apparatus may be formed of stainless steel. The tube 2 is typically about 115 mm. long, with an internal diameter (for example the hole) of about 6 mm. and an external dimension of about 10 mm. square. Blocks 51 are typically about 28 mm. square, and about 15 mm. Wide. Six of these blocks are used, as shown in the drawing, with a space 59 of about 1 mm. between the adjacent blocks. Alternatively, a large number of thin blocks can be used (for example, twenty blocks with a width of 7 mm.). It can be appreciated that any of the apparatuses shown in Figs. 3 to 6 and 10 may be used in the test pack of Fig. 7 (instead of the apparatus of Figs 1 and 2). Furthermore, not only the evaluation apparatus of Fig. 4 can be used as illustrated in Figs. 8 and 9; any of the other evaluation devices can be used in this way. Generally, it has been found that evaluation apparatuses of the type shown in the drawings have some delay in reaction when changing the conditions that exist in the sterilization chamber during a sterilization cycle. It is believed that it is important when an evaluation device is used in a test package where it issues a simple "pass / fail" decision on the effectiveness of a sterilization cycle since the decision may be based on conditions at a later stage cycle, instead of an initial stage. It has been found, particularly when using evaluation equipment of the type shown in Fig. 10, that a reliable "pass / fail" decision can be made based on temperature measurements only and that moisture measurements are not essential . This is considered to be advantageous, giving much greater availability for the highly reliable temperature detectors. Furthermore, in the apparatus of Fig. 10 in particular it has been found that the exact location of the detector is not critical to provide a reliable "pass / fail" decision made. Although the evaluation apparatus of Figs 1 through 6 and 10 are shown in the preferred orientation because this allows the condensate to drain from the orifice this orientation is not essential. As a further modification, some form of the moisture absorbing material can be provided on the walls of the hole. Also, although the description described above refers to the use of the evaluation apparatuses that have been placed inside a sterilization chamber, this is the same non-essential. The evaluation apparatuses of the type described above can be placed outside of a sterilizer (for example, attached to the drain line) with the open end of the orifice which is in communication through a suitable connection with the interior of the sterilization chamber. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following

Claims (17)

1. CLAIMS 1. A sterilizer evaluation apparatus for use in a sterilizer to determine the efficiency of the air removal step of a sterilization cycle, characterized in that the apparatus comprises a passage that is closed at one end and open at the other end for the entry of the sterilant into the passage, and means for mounting a detector for detecting the presence of sterilant at a predetermined location downstream of the closed end of the passageway; wherein the walls of the passage are formed of a thermally insulating material and the apparatus further comprises a heat absorbing portion surrounding the passage and, when the apparatus is in use within a sterilizer, preferably receives heat from within the passageway; from there the penetration of the sterilant from the open end of the passage to said predetermined place during a sterilization cycle is inhibited by the accumulation of air and / or non-condensable gas within the passage resulting from the condensation of moisture on the walls of the camera.
2. 2. An apparatus as claimed in claim 1, characterized in that the heat absorbing part is surrounded by a thermally insulating part according to which, during a sterilization cycle, the heat absorbing part can preferably receive heat from within the passage.
3. 3. An apparatus as claimed in claim 2, characterized in that the thermally insulating part comprises an outer covering (20) that surrounds and is spaced from the heat absorbing part, the space contains a thermally insulating material.
4. 4. An apparatus as claimed in claim 2, characterized in that the thermally insulating part comprises an outer covering (20) that surrounds and is separated by a space with air from the heat absorbing part.
5. 5. An apparatus as claimed in any of the preceding claims, characterized in that in the heat absorbing part it is formed of a thermally insulating material.
6. 6. An apparatus as claimed in any of the preceding claims, characterized in that in the heat absorbing part it includes a thermally conductive material.
7. 7. An apparatus as claimed in any of claims 1 to 4, characterized in that the passage is a hole in a tube (2) of thermally insulating material, and in which the heat-absorbing part is placed around the tube.
8. 8. An apparatus as claimed in claim 7, characterized in that the heat absorbing part comprises a plurality of thermally conductive masses (51) placed around the tube along it, the masses are thermally separated one from the other.
9. 9. An apparatus as claimed in claim 8, characterized in that it includes a temperature sensor positioned to detect the temperature in one of the thermally conductive masses at or adjacent to the closed end of the tube, and according to which it detects the presence of sterilant in the region adjacent to the tube orifice.
10. 10. An apparatus as claimed in claim 8, characterized in that wherein the passage is formed within a mass of material that also provides a heat absorbing part, the material having a thermal capacity such that the ratio of the thermal capacity to the Thermal conductivity is within the range from 1 x 10 to 12 x 10 sec. / m.
11. 11. An apparatus as claimed in claim 12, characterized in that it includes a temperature sensor positioned to detect the presence of sterilant in, or adjacent to, the closed end of the passage.
12. 12. An apparatus as claimed in any of claims 1 to 4, characterized in that the passage comprises a plurality of interconnected compartments, the opening for the entry of the sterilant is in one of the interconnected compartments, and the predetermined location in another.
13. 13. An apparatus for evaluating the sterilant for use in a sterilizer for determining the efficiency of the air removal stage of a sterilization cycle, characterized in that the apparatus comprises a passage that is closed at one end and open at the other end for the inlet of the sterilant within the passage, and means for mounting a detector for detecting the presence of sterilant at a predetermined location downstream of the closed end of the passageway; the passage is formed within a heat absorber, which is surrounded by the thermal insulator whereby, when the apparatus is in use in a sterilizer, the heat absorber preferably receives heat from within the passage, the heat absorber is constructed to provide a plurality of thermally placed masses positioned along the passageway and thermally spaced from each other in this direction whereby the penetration of sterilant from the open end of the passage to said predetermined location during a sterilization cycle is inhibited by the accumulation of air and / or non-condensable gas within the unoccupied space resulting from the condensation of moisture on the walls of the chamber.
14. 14. An apparatus as claimed in claim 13, characterized in that the passage is the orifice in a tube of thermally insulating material, and the thermally conductive masses comprise thermally conductive blocks around the tube and separated from each other by air spaces.
15. 15. An apparatus as claimed in claim 13 or claim 14, wherein the thermal insulator surrounding the heat absorber comprises an outer covering which surrounds, and is separated from these by an air gap, the heat absorber.
16. 16. An apparatus as claimed in claims 13 to 15, characterized in that it includes a temperature sensor placed in one of the thermally conductive masses at or adjacent to the closed end of the passage, to detect the temperature in the thermally conductive mass and according to which detects the presence of sterilant in the region adjacent to the orifice of the tube.
17. 17. An apparatus as claimed in claim 16, in combination with a second temperature sensor positioned to detect the temperature in a sterilization chamber in which the apparatus is placed. SUMMARY A sterilizer evaluation apparatus (50), for use in the efficiency test in the air removal stage of a sterilization cycle within a sterilizer, includes a tube (29 of thermally insulating material, the orifice is closed in a end (52) and open in the other for the sterilizer inlet A plurality of thermally conductive masses (51) are placed around the tube (2) and thermally separated from each other by an air space (59), and is placed a temperature sensor in an inlet (61) in one of the masses adjacent to the closed end of the tube An outer cover (25) defines an air space around the thermally conductive masses and thermally insulated the masses of the heat inside the sterilizer When the evaluation chamber is placed in a sterilizer, the penetration of sterilant along the orifice of the tube (2) during a sterilization cycle, is inhibited by the accumulation of air and / or non-condensable gas within the hole resulting from the condensation of moisture on the walls of the orifice. By measuring the temperature within a thermally conductive mass (51) adjacent to the closed end of the tube (2), the presence of sterilant can be detected in the region of the orifice of the tube.