Abstract:
A process challenge device (PCD) for determining the effectiveness of a microbial deactivation process that uses a vaporous deactivating agent (e.g., vaporized hydrogen peroxide) as a deactivating agent. The PCD includes first and second layers that are joined together to form (1) a chamber dimensioned to receive a biological and/or chemical indicator, and (2) first and second conduits fluidly connecting the chamber with a region outside the PCD. Each conduit has one end in communication with the region outside the PCD and another end in communication with the chamber. A removable seal member seals the biological and/or chemical indicator inside the chamber.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to monitoring of a biocontamination deactivation process, and more particularly to a process challenge device for assessing the effective performance of a biocontamination deactivation process. 
     BACKGROUND OF THE INVENTION 
     Medical instruments (such as dental, pharmaceutical, veterinary, and mortuary devices) that are exposed to blood or other bodily fluids require thorough cleaning and microbial deactivation between each use. Medical instruments may be microbially deactivated by exposure to a gaseous or vaporous deactivating agent, such as vaporized hydrogen peroxide, during a microbial deactivation process. For a medical instrument to be successfully deactivated during a microbial deactivation process, all surfaces of the medical instrument must be exposed to a predetermined minimum concentration of vaporized hydrogen peroxide for a predetermined minimum period of time. 
     Some surfaces of medical instruments are difficult to expose to the vaporous deactivating agent because of the shape, i.e., geometry, of the instrument. For example, for instruments having lumens, it is difficult to expose the inner surfaces of the lumens to the vaporous deactivating agent. As a result, a microbial deactivation process may not be effective because such surfaces have not been successfully deactivated by appropriate exposure to the vaporous deactivating agent. 
     A process challenge device (also commonly referred to as a “test pack”) is designed to simulate an item being deactivated and to constitute a defined challenge to the microbial deactivation process. In order to assess the effectiveness of a microbial deactivation process a process challenge device (PCD) is placed within a deactivation chamber along with the instruments being deactivated. A PCD includes a housing and a biological indicator (BI) and/or a chemical indicator (CI), that are placed inside the housing. The housing includes internal passageways that create a challenge to the microbial deactivation process that is representative of the most difficult item to deactivate in a load. Following completion of a microbial deactivation process, the biological indicator and/or chemical indicator are analyzed in a known manner to determine the effectiveness of the microbial deactivation process. 
     A conventional PCD housing includes a narrow internal passageway formed therein that has an open end and a closed end. The open end of the passageway is in fluid communication with a region external to the housing. A BI and/or CI is disposed at the closed end of the passageway. During a microbial deactivation process, vaporized deactivating agent can travel from the region external to the housing, along the passageway, and to the BI and/or CI located at the closed end of the passageway. 
     One problem with existing PCD housings is that the passageway leading to the BI and/or CI can become partially or fully blocked, thereby causing the BI and/or CI to provide inaccurate results concerning the effectiveness of the microbial deactivation process. The passageway within the housing can become blocked as the result of several conditions. For example, condensation of the vaporous deactivating agent within the passageway can result in blockage of the passageway. The passageway can also become blocked when the walls defining the passageway collapse or are drawn into the passageway in response to pressure changes during the microbial deactivation process. For example, a known PCD housing includes a layer of flexible plastic film that defines a wall of the passageway. During a deactivation process, the flexible plastic film may collapse or be drawn into the passageway when the PCD is exposed to large changes in pressure, thereby reducing the diameter of the passageway. A PCD having a passageway with a reduced diameter provides a challenge greater than the most difficult item to deactivate in the load. Accordingly, the BI and/or CI may not provide accurate results. 
     Another problem with existing PCD housings is that the BI and/or CI of the PCD may not be exposed to the same concentration of vaporous deactivating agent (e.g., vaporized hydrogen peroxide) as the surfaces of the instruments being deactivated. It is believed that this inconsistency results from inadequate circulation of the vaporous deactivating agent within the PCD housing, as compared to the circulation of vaporous deactivating agent within the item (e.g., a lumened instrument) being deactivated. 
     The present invention overcomes these and other problems by providing a PCD that maintains a challenge to microbial deactivation that is representative of the most difficult item to deactivate in a load and can provide fluid circulation therein to provide appropriate exposure to a biological and/or chemical indicator. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the present invention, there is provided a process challenge device for evaluating the effectiveness of a microbial deactivation process using a vaporous deactivating agent, the device comprising: a housing including: (a) a first layer, and (b) a second layer, wherein said first layer and said second layer are fixed to each other to define: (i) a chamber dimensioned to receive at least one of the following: a biological indicator and a chemical indicator, (ii) a first conduit having one end in fluid communication with said chamber and having an open end, and (iii) a second conduit having one end in fluid communication with said chamber and having an open end. 
     In accordance with another embodiment of the invention, there is provided a process challenge device for evaluating the effectiveness of a microbial deactivation process using a vaporous deactivating agent, the device comprising: (1) a housing including: (a) a first layer, and (b) a second layer fixed to the first layer, said first and second layers defining: (i) a chamber sealed by a removable seal member, (ii) a first tortuous conduit having one end in fluid communication with a first end of the chamber, and an open end, and (iii) a second tortuous conduit having one end in fluid communication with a second end of the chamber, and an open end; and (2) a least one of the following located in said chamber: a biological indicator and a chemical indicator. 
     An advantage of the present invention is the provision of a PCD for determining the effectiveness of a deactivation process that uses vaporized hydrogen peroxide to microbially deactivate medical instruments. 
     Another advantage of the present invention is the provision of a PCD housing that includes a passageway with two (2) open ends. 
     Still another advantage of the present invention is the provision of a PCD housing including a passageway defined therein by walls that are resistant to collapse in response to pressure changes. 
     Still another advantage of the present invention is the provision of a PCD housing having a passageway defined therein that is arranged to minimize condensation of a vaporous deactivating agent therein. 
     Still another advantage of the present invention is the provision of a PCD housing providing improved circulation of a vaporous deactivating agent therein. 
     Yet another advantage of the present invention is the provision of a PCD housing that allows convenient removal of biological and/or chemical indicators from the PCD housing. 
     Yet another advantage of the present invention is the provision of a PCD that can be manufactured simply and efficiently. 
     These and other advantages will become apparent from the following description of one embodiment taken together with the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may take physical form in certain parts and arrangement of parts, one embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein: 
         FIG. 1  is a perspective view of a PCD, illustrating one embodiment of the present invention; 
         FIG. 2  is a top plan view of the PCD shown in  FIG. 1 ; 
         FIG. 3  is a side plan view of the PCD shown in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the PCD taken along lines  4 - 4  of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view of the PCD taken along lines  5 - 5  of  FIG. 2 ; 
         FIG. 5A  is a cross-sectional view taken along lines  5 - 5  of  FIG. 2  illustrating an alternative embodiment of the PCD; 
         FIG. 6  is an exploded view of the PCD shown in  FIG. 1 ; and 
         FIG. 7  is a perspective view of the PCD showing removal of indicators therefrom. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein the showings are for the purpose of illustrating one embodiment of the invention only and not for the purpose of limiting same,  FIGS. 1-3  show a process challenge device (PCD)  10  according to one embodiment of the present invention. PCD  10  includes a housing  15  and an indicator device, such as a biological indicator (BI)  12  and/or a chemical indicator (CI)  14 . Housing  15  is generally comprised of a first layer  20  and a second layer  120 , as best seen in  FIGS. 3 and 6 . 
     First layer  20  is a generally planar sheet having a first end  26  and a second end  28 . In the illustrated embodiment, a side wall  22  extends from the peripheral edge of first layer  20 , and a flange  24  extends outward from side wall  22 . Side wall  22  and flange  24  provide additional structural rigidity to first layer  20 . 
     A recess  30 , a first channel  40  and a second channel  60  are formed in first layer  20 . Recess  30  has a first end  32  and a second end  34 . In the illustrated embodiment, recess  30  is generally located in the center region of first layer  20 . Recess  30  is dimensioned to receive BI  12  and/or CI  14 . 
     First channel  40  extends between first end  26  of first layer  20  and first end  32  of recess  30 . Accordingly, first channel  40  has an outer end  42  located at first end  26  of first layer  20  and an inner end  44  located at first end  32  of recess  30 . Similarly, second channel  60  extends between second end  28  of first layer  20  and second end  34  of recess  30 . Accordingly, second channel  60  has an outer end  62  located at second end  28  of first layer  20  and an inner end  64  located at second end  34  of recess  30 . In the illustrated embodiment, first channel  40  includes generally straight portions  46  and bent portions  48 . Likewise, second channel  60  includes generally straight portions  66  and bent portions  68 . It should be appreciated that first and second channels  40 ,  60  can be formed in tortuous shapes other than as shown in the figures. 
     As best seen in  FIGS. 3 and 6 , second layer  120  is a generally planar sheet having dimensions similar to first layer  20 . An opening  122  is formed in second layer  120 . A seal member  140  covers opening  122 , as will be described in detail below. It is contemplated that seal member  140  may be made of various different materials, including, but not limited to, a metal foil, a thermoplastic having a metallic layer deposited thereon, or a combination thereof, as well as polypropylene sheeting. 
     Second layer  120  is fixed to the lower surface of first layer  20 , such that opening  122  generally aligns with recess  30 , as best seen in  FIG. 6 . It is contemplated that second layer  120  may be fixed to first layer  20  in a variety of different ways, including, but not limited to, ultrasonic welding, solvent welding, an adhesive, or a combination thereof. 
     Opening  122  of second layer  120  is dimensioned to allow BI  12  and CI  14  to pass therethrough for insertion and removal from recess  30 . Seal member  140  covers opening  122  to seal BI  12  and/or CI  14  within recess  30 . An adhesive is preferably used to attach seal member  140  to second layer  120 . Seal member  140  may be punctured, torn or peeled away to allow removal of BI  12  and CI  14  from recess  30  following a microbial deactivation process. 
     First layer  20  and second layer  120  are preferably formed of a generally rigid, thermoplastic material, including, but not limited to, polypropylene, polyethylene, polystryrene, and polyvinyl chloride (PVC). 
     It is contemplated that first layer  20  and second layer  120  may be alternatively formed from a single sheet that is folded to join first layer  20  to second layer  120 . In this alternative embodiment, first layer  20  and second layer  120  are joined along a common edge. 
     When first layer  20  is fixed to second layer  120 , first channel  40  and second layer  120  define a first conduit  52 , and second channel  60  and second layer  120  define a second conduit  72 , as best seen in  FIGS. 1 and 2 . Recess  30  of first layer  20 , second layer  120 , and seal member  140  define a chamber  132  when first layer  20  is fixed to second layer  120 . First conduit  52  has an open end  54  at one end thereof and is in fluid communication with chamber  132  at the other end thereof. Likewise, second conduit  72  has an open end  74  at one end thereof and is in fluid communication with chamber  132  at the other end thereof. In accordance with a preferred embodiment, first and second conduits  52 ,  72  each have an inner diameter (ID) in the range of 1 to 2 mm, and each have a total length L in the range of 25 to 50 cm. Inner diameter ID and length L are preferably selected to be similar to the dimensions of a lumen of an instrument being deactivated. In the illustrated embodiment the respective lengths L and diameters ID of first conduit  52  and second conduit  72  are substantially the same. 
     First conduit  52 , second conduit  72  and chamber  132  collectively define a continuous serpentine or tortuous pathway extending between open ends  54  and  74  to allow fluid flow through PCD  10 . 
     In accordance with an alternative embodiment of the present invention shown in  FIG. 5A , second channel  60 A is defined by a plurality of depressions  69  formed in first layer  20 . Likewise, first channel (not shown) is defined by a plurality of depressions (not shown) formed in first layer  20 . In the illustrated embodiment, first layer  20  is attached to second layer  120  at the plurality of depressions  69 . 
     In accordance with yet another alternative embodiment of the present invention it is contemplated that portions of first and second channels  40 ,  60  may be defined by second layer  120 . Furthermore, it should be appreciated that first and second channels  40 ,  60  may be defined by portions of both first layer  20  and second layer  120 . 
     In the illustrated embodiment, BI  12  is a conventional self-contained indicator device that includes a source of viable microorganisms, i.e., a biological challenge, and a source of nutrients. The source of nutrients is contained within a vapor impermeable container. The source of microorganisms is not exposed to the source of nutrients, unless the vapor impermeable container is opened, i.e., broken. The source of viable microorganisms is exposed to vaporous deactivating agent entering recess  30 . 
     In the illustrated embodiment, CI  14  is a conventional indicator device comprised of a generally planar sheet that is coated or impregnated with a reactive chemical substance. The reactive chemical substance is selected such that a visual indication (e.g., a color change) results from exposure to a vaporous deactivating agent, such as vaporized hydrogen peroxide. 
     Assembly of PCD  10  will now be described with reference to  FIG. 6 . First layer  20  and second layer  120  are aligned with each other such that recess  30  of first layer  20  is aligned with opening  122  of second layer  120 . As indicated above, first layer  20  and second layer  120  are fixed to each other by such means as ultrasonic welding, solvent welding, an adhesive, or a combination thereof. BI  12  and/or CI  14  are inserted through opening  122  of second layer  120 , and placed inside recess  30  of first layer  20 . Seal member  140  is then placed over opening  122  and fixed to second layer  120 , preferably by use of an adhesive. 
     The present invention will now be described with respect to the operation of PCD  10 . Generally, a deactivation device (e.g., a sterilization system), is used to expose medical instruments and devices to a microbial deactivating agent for microbial deactivation. The present invention is described herein with reference to a deactivation device that uses vaporized hydrogen peroxide as the deactivating agent. However, it will be appreciated that the present invention may be used in connection with deactivation devices that use other types of deactivating agents. 
     An instrument is placed within a deactivation chamber of the deactivation device, along with PCD  10 . Vaporized hydrogen peroxide is injected into the deactivation chamber during a deactivation process to expose the instrument to vaporized hydrogen peroxide, thereby effecting microbial deactivation. Vaporized hydrogen peroxide entering the deactivation chamber also enters first and second conduits  52 ,  72  of PCD  10  via open ends  54  and  74 . Vaporized hydrogen peroxide entering first and second conduits  52 ,  72  flows along a portion of a tortuous pathway to chamber  132 , thereby exposing BI  12  and CI  14  to the vaporized hydrogen peroxide. As a result, the source of viable microorganisms within BI  12  is exposed to the vaporized hydrogen peroxide. 
     During portions of a deactivation process a vacuum may be drawn within the deactivation chamber in order to evacuate the deactivation chamber. For example, the pressure within the deactivation chamber may be reduced to less than 1 Torr. The use of a rigid material for first and second layers  20  and  120  prevents a collapse that may result in a partial or complete blockage of first conduit  52 , second conduit  72  or chamber  132 . 
     After the deactivation process has been completed, PCD  10  is removed from the deactivation chamber. Seal member  140  is either removed, punctured or peeled away to allow removal of BI  12  and CI  14  from recess  30 , as shown in  FIG. 7 . 
     It should be appreciated that CI  14  may be visually inspected while located within recess  30  if first layer  20 , second layer  120 , and/or seal member  140 , are made of a transparent material. 
     Following removal from recess  30 , BI  12  may be activated by breaking the impermeable container or otherwise opening the impermeable container that contains the source of nutrients. In this manner, the microorganisms are exposed to the nutrients. BI  12  is then incubated for an incubation period of predetermined duration. If microorganisms within BI  12  are not deactivated by exposure to vaporized hydrogen peroxide during the deactivation process, the microorganisms will grow during an incubation period. Subsequent examination of BI  12  will determine whether any microorganism growth has occurred. Microorganism growth indicates that the deactivation process was ineffective and that the instruments exposed to the vaporized hydrogen peroxide along with PCD  10  were not effectively deactivated. 
     It should be appreciated that the dimensions of first conduit  52 , second conduit  72  and chamber  132  are preferably selected such that PCD  10  simulates a “worst-case” instrument, i.e., an instrument having a geometry that is the most difficult to successfully deactivate by exposure to a vaporous microbial deactivating agent. Therefore, if PCD  10 , as a worst-case instrument, is successfully deactivated during a deactivation process, then it follows that the instruments exposed to that same deactivation process were also successfully deactivated. Accordingly, if BI  12  shows no microorganism growth during the incubation period, then all microorganisms within BI  12  were deactivated during the deactivation process. Thus, it can be concluded that the instruments undergoing the same deactivation process have also been successfully deactivated. 
     The foregoing descriptions are specific embodiments of the present invention. It should be appreciated that these embodiments are described for purposes of illustration only, and that those skilled in the art may practice numerous alterations and modifications without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.