Abstract:
A method of and system for sterilizing the internal surfaces of one or more elongate relatively narrow passages of interest contained in a device of interest, said passages having end openings and being susceptible of sustaining flow there along by inducing a positive flow of sterilizing gas through each passage of interest in a selected direction. Gas flow through a device of interest is caused by a passive two-chamber device which generates a transient pressure gradient between the ends of the lumens of the device in response to externally imposed variations of pressure. Sterilant gas is provided from outside the two chamber systems.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [1]    1. This application is a continuation-in-part of application Ser. No. 09/135,146 filed Aug. 17, 1998. That application is deemed incorporated by referenced herein in its entirety.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [2]    2. Field of the Invention  
           [3]    3. The present invention relates generally to gas phase (vapor) sterilization and, more particularly, to disinfecting and sterilizing devices having elongate, narrow passages or lumens accessible from both ends such as those commonly associated with vascular catheters endoscopes and similar devices. While the entire device must be sterilized, the invention is primarily concerned with the successful sterilization of the more difficult internal surfaces concurrently with sterilization of the exterior. The invention employs techniques that produce a flow of sterilizing gas through the internal passage or passages in a given load (items to be concurrently sterilized) during processing which results in a rapid and complete exposure of internal passage or channel surfaces of each item of the load to the sterilant vapor by transforming each lumen or other channel or passage of interest into a flow channel for the sterilant gas during successive evacuation and pressurization cycles.  
           [4]    4. Related Art  
           [5]    5. The need to sterilize articles such as medical devices and instruments following manufacture and initial packaging for use or prior to reuse after contacting a patient has long been recognized. Traditional methods of sterilization include immersion of the article or instrument of interest in a sterilizing solution or the use of various techniques involving elevated temperatures. More recently, however, it has been recognized that chemical vapor sterilization at lower temperatures is generally better suited to today&#39;s more sensitive and sophisticated instrumentation and materials of construction. Moreover, financial constraints placed generally on medical care providers presently produce situations in which “single-use” items previously discarded after the first patient are now being resterilized and reused.  
           [6]    6. While vapor sterilization has offered several distinct advantages over other forms, one major disadvantage heretofore associated with the technique involves an inability to conduct sufficient sterilizing vapor to contact the central internal surfaces of rather long and narrow passages such as the lumens of catheters and endoscopes in an expeditious manner. Typically, present systems operate by partially evacuating the sterilization chamber prior to the introduction of the sterilizing material in a repressurization step. The chamber may be subjected to a series of evacuation and pressurization cycles in this manner. Complete sterilization of the internal surfaces depends on diffusion of the sterilant gas, which might be ethylene oxide or another material usually diluted in a carrier gas along the passages from the open ends to produce sufficient antimicrobial activity at the midpoint of each narrow passage. Unfortunately, normal diffusion and other mixing techniques are simply too slow to accomplish reliable sterilization at passage midpoints within desired time constraints and this may offset other advantages of vapor sterilization. The problem is documented, for example, in Alfa, M. J., “Changes In Hospital Practice”,  Biomedical Instrumentation and Technology  (September/October 1996) and Alfa, M. J. et al, “Comparison of Ion Plasma, Vaporized Hydrogen Peroxide, and 100% Ethylene Oxide Gas Sterilizer”,  Infection Control And Hospital Epidemiology  (February 1996).  
           [7]    7. Several ways of overcoming the above disadvantage have been proposed with respect to vapor sterilization of relatively long and narrow passages. In one technique, a closed vessel containing a small amount of a vaporizable antimicrobial fluid is attached to one end of an endoscope or other device lumen. A seal is breached in the vessel and the other end of the lumen is exposed to a reduced pressure. This allows antimicrobial vapor to flow along the length of a lumen from the source toward the open end. Such a technique is shown in U.S. Pat. Nos. 5,580,530 and 5,733,503 to Kowatsch et al and in Jacobs et al (U.S. Pat. No. 4,943,414). Another technique shown in Childers et al (U.S. Pat. No. 5,527,508) discloses a pressure modulation technique using a low vapor pressure chemical vapor sterilant in conjunction with a compression carrier gas to promote diffusion in a pressure modulation cyclic sequence. Meanwhile, manufacturers of these devices have been resorting to drastically extended gas sterilization cycles, sometimes taking days to complete, to insure sterility of their device products.  
           [8]    8. While these previous techniques have met with some success, there remains a need for a method and system that provides more certain and immediate contact between the sterilizing vapor and the internal passage surfaces, particularly the surfaces nearest the midpoint of the passages, to enable the surfaces to be sterilized in an expeditious manner which need not depend on internal diffusive mixing equilibrium.  
           [9]    9. With regard to certain terminology used in this specification, definitions seem appropriate. The terms “sterilant gas or sterilant vapor” or “sterilizing gas or sterilizing vapor”, as used in this specification, refer to any substance, whether true gas or vapor of a volatile liquid, which is capable of sterilizing the load of interest and which is in the gaseous state under use conditions. It may consist of a single active ingredient or a mixture of ingredients, and may contain inactive diluents or carriers. Also, the term “lumen”, “channel”, “passage”, or the like, refers to any internal passage accessible from both ends which is relatively long in relation to its diameter and therefore difficult to readily sterilize near or at its midpoint by diffusion of a sterilant gas from the ends. “Cassette” refers to any relatively compact package form suitable for containing and adapted to receive any of the class of devices (having integral elongate passages) suitable for sterilization and/or storage in accordance with the invention. The cassettes may be of any convenient shape and are assumed to be of sufficient rigidity to withstand the necessary pressure differential used in the method of the invention and the term includes, without limitation, the common rectangular shaped containers. The term “sterilization” means a sufficient reduction in the live microbe and/or spore population to render the device of interest to be safe for its intended use. This is normally a 7-9 log 10  reduction of the bacteria and/or spore population.  
           [10]    10. Accordingly, a primary object of the present invention is to provide an improved method of vapor sterilization particularly suited to the sterilization of devices of interest having internal surfaces including relatively long, narrow passages characteristic of the lumens of catheters and endoscopic instruments, together with devices for carrying out the method.  
           [11]    11. Another object of the present invention is to provide an improved method of vapor sterilization that is based on inducing a reversible positive flow of sterilant vapor throughout the length of a passage of interest to be sterilized.  
           [12]    12. Yet another object of the present invention is to establish a positive flow of sterilant vapor throughout the length of a passage to be sterilized by inducing an end-to-end pressure differential to an open-ended passage to be sterilized by exposing each end to a different time variable (transient) pressure function to transform the passage into a flow channel and to promote flow therethrough to produce immediate antimicrobial activity along the entire length of the passage.  
           [13]    13. Still another object of the present invention is to accomplish the method of the invention using only a passive partitioned cassette to contain the device of interest and a vacuum/pressurization chamber to contain the cassette.  
           [14]    14. Yet still another object of the present invention is to provide a close tolerance passage or gas permeable collar at the partition wall within the cassette so as to achieve sterilization of the area of the device contacting the partition.  
           [15]    15. A further object of the present invention is to produce a time variable (transient) end-to-end pressure differential in each open-ended passage to be sterilized on a reversing basis.  
           [16]    16. A still further object of the present invention is to provide a partitioned two-chamber cassette to contain a device having an elongate passage to be sterilized with one end in each chamber having gas permeable accesses in each chamber to be exposed simultaneously to vacuum/pressurization sterilization cycling in which the combination of the relative chamber sizes and permeabilities can be used to determine the time variable pressure difference between the chambers.  
           [17]    17. These and other objects, as well as these and other features and advantages of the invention, will become apparent to those skilled in the art upon familiarization with the specification, drawings and claims contained herein which are meant to exemplify but not to limit the scope of the present invention in any manner.  
         SUMMARY OF THE INVENTION  
         [18]    18. The present invention provides a new method and apparatus for achieving timely total gas or vapor sterilization in devices generally having internal passages which are difficult to sterilize utilizing diffusion techniques. These include, for example, the elongated lumens of vascular catheters and the interior passages of endoscopes. The present invention achieves rapid vapor sterilization by providing for immediate and complete contact between the internal surfaces of the instrument passages and the sterilizing vapor by providing means which produce a flow of sterilant gas in and throughout the entire length of the passage of interest to be sterilized. The present invention enables a variety of open-ended passages including the long, narrow tubes or instrument passages of endoscopes or catheter lumens to be dependably sterilized internally in a timely manner even at the most difficult central portion of the load. The method adapts to a number of apparatus embodiments, some of which are illustrated in the detailed description by way of example, and lends itself to the use of existing equipment.  
           [19]    19. The present invention introduces a method and apparatus for gas phase sterilization of elongated tubular devices of interest in which sterilant gas flow through lumens of the devices of interest is induced by a flow-dependent transient pressure gradient set up between the ends of the lumens. The transient pressure gradient can be created by exposing each end of each lumen to a separate chamber and concurrently evacuating or concurrently pressurizing both chambers at different effective rates. A preferred method is one in which each end of a passage of interest in a device to be sterilized is subjected to a different transitory pressure change function when a sterilization container containing the device is exposed to a vacuum or pressurization step thereby producing a transitory pressure gradient function between passage ends which transforms the passage of interest into a flow channel and induces a flow of sterilant gas along the length of the passage. The different transitory pressure change functions may be produced in any of a number of ways which result in the net effect of a pressure gradient which typically operates to induce a flow of sterilant material in one direction when the ambient pressure is reduced as by a vacuum pump or in the opposite direction when the pressure is increased by the introduction of sterilant gas.  
           [20]    20. A device to be sterilized is generally loaded into a storage container, preferably in the form of a cassette, which may be of a design unique to that species of device. The container is provided with two compartments or chambers of equal or unequal, but relatively fixed size. At least one of the chambers has an area of vapor permeability that accesses the volume outside the cassette. When a device is loaded for sterilization, one end of each of the elongate passages or lumens of interest is situated in each chamber. By modulating the pressure outside the cassette, both chambers are subjected to evacuation/pressurization cycles with sterilant gas being added in the pressurization cycles in a manner that effectively affects the chambers according to different transitory pressure change functions and thereby induces a flow between the chambers in the passages of interest. Flow in one direction during evacuation reverses during pressurization.  
           [21]    21. The chamber sizes and difference in the transitory pressure change functions are preferably sufficient to cause at least one complete volume change in all passages of interest. It will be appreciated that a net flow that amounts to less than one volume change will also eventually result in sterilization in accordance with the invention; however, additional cycles and thus a longer sterilization time will be required with lesser flow amounts. As used herein, net flow means the flow through the passages of interest during one pressurization or evacuation cycle. Flow through the passage of interest can be accomplished in a number of ways. If the two cassette compartments are unequal in size, evacuating or pressurizing them at the same volumetric rate will produce a different rate of pressure change in the compartments to produce the desired effect. Of course, to produce a volume change, the smaller volume chamber must still have a volume that exceeds the total volume of the passages to be sterilized. If the cassette compartments are not sufficiently unequal in size, relatively diverse volumetric flow rates for evacuation/pressurization can be used to compensate. Relative flow rates can be adjusted in a number of ways according to the invention. For example, the two chambers of the cassette may be provided with gas permeable accesses of different capacities and the cassette exposed to the cycle steps within a common larger sterilizing chamber or the chambers may be connected to vacuum/pressurization devices that effectively treat them unequally due to size of connection, relative permeability, etc.  
           [22]    22. Direct cross flow through the barrier between the chambers is minimized by a low clearance fit or by sealing devices between the item to be sterilized and the barrier wall. The seal is preferably a resilient, but porous material such as a foam material that allows seepage but not direct flow. However, a relatively low clearance fit may also be used. It is an important aspect of the invention that the entire device be sterilized and, accordingly, sterilant material must readily reach and sterilize that segment of the device which is in the vicinity of the barrier or partition, either directly or through a porous material. It is noteworthy that the method can manifest itself in any of a variety of devices and technique combinations and offers a new practical solution to a long-standing problem.  
           [23]    23. In accordance with the operation of the device or method of the invention, when the assembly is evacuated, gas will flow from both chambers, however, since the time related transient flow function for each is different, the pressure within one chamber will drop faster than that within the other chamber. This temporary pressure differential will induce a net flow of gas throughout the length of the tubes or passages to be sterilized inside the cassette. Conversely, upon repressurization with sterilant gas, the net flow will reverse as the same chamber will fill more readily. By cycling the system, this technique produces two-way time varying or transient, reversing flow of relatively full strength sterilant gas to maintain high antimicrobial activity along the entire length of the device to be sterilized. The rate of depletion of sterilant material potency in use should also be considered in arriving at ideal cycle times. The typical pressure range for the operation of the process may cycle from less than 1 Torr to several atmospheres.  
           [24]    24. The required time and number of cycles also will vary with the type of items to be sterilized and the previous histories of those items. Typically, 2 to 5 evacuation/pressurization steps are required.  
           [25]    25. Of course, the open-ended internal passages or lumens of interest need not run the length of the device; they only need straddle the barrier between the chambers. Thus, guidewire or other shorter lumens contained some devices in addition to much longer lumens may be sterilized by proper placement of the device so that one access opening is on either side of the barrier.  
           [26]    26. Any sterilant material compatible with the material of the endoscope or other device being sterilized may be employed as the sterilizing vapor. For example, one may employ ethylene oxide (ETO), hydrogen peroxide (H 2 O 2 ), formaldehyde (HCHO) or a variety of peracid materials such as those disclosed in applicant&#39;s copending application, Ser. No. 08/032,606, filed Mar. 17, 1993, now U.S. Pat. No. 6,036,918, issued Mar. 14, 2000. Purge cycling, as required, is used to remove chemical sterilants after sterilization.  
           [27]    27. Of course, those skilled in the art will recognize that sterilant material is consumed by impurities during the sterilization process which, in turn, reduces the strength or anti-microbial capacity or potency of the gas unless the sterilant is replenished. This is particularly true in confined spaces. The flow-through system of the invention changes the gas within even the most clandestine central passage spaces often enough to enable the strength of the sterilant to be maintained at a relatively high level throughout the load during the process.  
           [28]    28. The invention may also operate using a single access. One single access embodiment that employs the technique of the present invention involves providing one end of an open-ended endoscope tube or other elongated open-ended hollow device to be treated with a closed chamber in the form of a removable gastight hollow fitting (cap or bulb) of internal volume greater than the internal volume of the device to be sterilized to assure sufficient flow through during sterilization. The hollow fitting preferably includes a gas permeable collar that fits over the endoscope tube or the end of another device of interest constructed so that the area under the collar is also exposed to the sterilant gas and the entire device is sterilized. This system is designed to be placed in a packaging container that, in turn, is itself placed entirely inside of a pressure variable gas sterilization chamber for processing. In this manner, the packaging container becomes a second chamber which contains the first, i.e., the larger chamber entirely contains the smaller with the passages of interest situated therebetween with respect to flow. A similar effect is realized when one compartment of the cassette embodiment is sealed and the entire system is forced to “breathe” through the other via the passages of interest.  
           [29]    29. During sterilization, the pressure is cycled on a time variable basis as with the cassette system previously described. The packaging container is first partially evacuated and thereafter the desired amount of active sterilant gas is admitted. Sterilant gas entering the chamber enters each partially evacuated lumen at the exposed open end thereof and flows through each entire device passage to equalize the pressure in the cap, bulb or closed cassette chamber volume thereby providing a fresh stream of sterilizing gas throughout the length of the tube. During subsequent evacuation stages of the sterilizer chamber, the stored excess of vapor within the volume of the cap, bulb or closed cassette chamber will flow out again sweeping through the entire length of the hollow lumen providing further contact with the entire inner surface.  
           [30]    30. Alternatively, the device may be enclosed in a gas permeable container or bag and the tightly fitting chamber placed over one end of the package so as to enclose one opening of the device lumens, the package or bag acting as a gas permeable collar. This embodiment is especially useful for endoscopes packaged to be stored hanging in a straight posture. It will be appreciated that the cassettes or other such devices of the present invention readily replace typical contemporary flow-through (gas permeable) sterile soft-sided packaging (some of which are also known as peel pouches), and which can be used with some single access versions of the present invention. The cassettes or cap or bulb devices should be rigid enough to resist flexure during cyclic pressure changes although large pressure differentials do not normally occur.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [31]    31. In the drawings, wherein like numerals are utilized to designate like parts throughout the same:  
         [32]    32.FIG. 1 illustrates schematically a perspective view of a two-compartment cassette system for accomplishing vapor sterilization in accordance with the invention;  
         [33]    33.FIG. 2 is a schematic perspective diagram of an enclosed lumen and bulb single access arrangement for a device to be sterilized in accordance with the invention;  
         [34]    34.FIG. 3 illustrates in perspective a greatly enlarged inter-chamber transition area as in FIG. 1 partially cut away to show portions of the interior and a gas-permeable layer;  
         [35]    35.FIGS. 4 and 5 schematically illustrate in perspective a further adaptation or variation useful for processing endoscopes;  
         [36]    36.FIG. 6 depicts in perspective an alternate embodiment of the cap or bulb of FIG. 2 or the container of FIG. 4 for receiving one end of a device to be sterilized;  
         [37]    37.FIG. 7 is a fragmentary perspective schematic representation of an embodiment utilizing a formed plastic tray and chamber arrangement for accommodating an elongated lumen device for sterilization;  
         [38]    38.FIG. 7A is a an enlarged perspective view of the chamber of FIG. 7;  
         [39]    39.FIG. 8 is a fragmentary schematic perspective view of a device similar to that in FIG. 7 in which the chamber is an integral part of the tray;  
         [40]    40.FIG. 9 is a fragmentary schematic perspective diagram illustrating another arrangement in which the lumen is contained in a medical bag attached to a partially external plastic chamber within a sterilizing environment; and  
         [41]    41.FIG. 10 is a fragmentary schematic perspective diagram similar to that in FIG. 8 wherein both the elongated lumen to be sterilized and the plastic chamber are contained within a gas permeable sealed peel pouch.  
     
    
     DETAILED DESCRIPTION  
       [42]    42. The present invention offers a method for gas phase sterilization of elongated tubular devices of interest, such as medical catheters and endoscopes, in which sterilant gas flow through the lumen(s) of the devices of interest is induced by creating a different transient pressure gradient function at each end of those lumens. The transient pressure gradient is preferably created by exposing each end of each lumen to a separate chamber and concurrently evacuating or concurrently pressurized both chambers at different effective rates. The method can be practiced using any of a variety of sterilization devices and provides new flow-through approaches to the total gas or vapor sterilization of relatively elongate narrow open-ended passages in medical and other devices requiring sterilization that enables rapid and total sterilization by virtue of providing a positive flow of sterilizing gas contacting all internal surfaces. As indicated, the approach is particularly suited to long and narrow passages with end openings, the central portions of which have heretofore challenged and resisted timely vapor sterilization because of the difficulty in accessing these regions with effective antimicrobial concentrations.  
         [43]    43. It will be appreciated that any suitable sterilant gas may be used in accordance with the present invention including ETO, H 2 O 2 , HCHO, ion plasma sterilizers, peracids, including performic acid, peracetic, perpropionic acid and mixtures thereof as more completely described in the above-cross referenced copending application. The techniques of the invention are particularly useful for cold sterilization which, as used herein, refers to procedures which effect sterilization at temperatures substantially below the 120-132° C. typically employed using high pressure steam techniques.  
         [44]    44. In addition, any suitable range of pressures may be employed in implementing the techniques of the invention, although a range which centers at or below one atmosphere is generally the easiest to implement. The process is also generally designed to enable operation at relatively low sterilization temperatures, i.e., below 100° C. and preferably below 70° C. In addition, any type of device having intricate internal passages which are openly accessible but difficult to reach by diffusion and which will admit to sterilization using the present invention are presumed to be intended to be included and those illustrated, together with the particular embodiments or devices to carry out the invention, are given by way of example and not limitation.  
         [45]    45.FIG. 1 depicts a preferred embodiment in which a hollow sterilizing cassette package or container having a body generally at  10  and a removable lid  11  is nominally subdivided into unequal compartments including a first small chamber or compartment  12  of volume V 1  and a second chamber or compartment  14  of volume V 2 . The cassette package including body  10  and lid  11  is shown inside a larger sterilization chamber shown as a transparent fragment at  16  of volume V 3  which is attached by one or more external accesses represented by  18  which represents both a gas admitting or supply system that includes a source of sterilizing and/or purge gas  36  and to a vacuum system (not shown) in a well-known manner. Separation of the compartments  12  and  14  is accomplished by a separator barrier or partition  20 . The separator  20  as indicated by the arrow  22  may be located in a variety of locations as shown in phantom at  20   a  and  20   b  depending on the desired relative sizes of V 1  and V 2  and generally contains one passage or opening therethrough, which is illustrated as having components or portions in the body  10  and lid  11  at  26  to accommodate an elongated, hollow tube  28  to be treated. The tube is situated with one open end  30  in the compartment  14  and the other open end  32  in the chamber  12 . When the cassette is assembled, the passage  26  should be snug with, but not in gastight relation to the tube  28 . A snug fit between the tube  28  and the barrier  20  minimizes direct flow between the chambers, but allows leakage for sterilization of the entire device is all that is necessary. External vapor-permeable areas accesses or ports connecting to the container  12  are represented for the chambers  12  and  14  respectively by  34  and  36 . The tube  28  represents any elongated device lumen or passage and the areas  34  and  36  represent accesses of any size or degree of permeability. It will be understood that the lid  11  and body  10  are provided with the necessary peripheral seals when assembled.  
         [46]    46. The embodiment of FIG. 1 is designed to operate by pressure modulation in the chamber  16  (V 3 ) using alternating evacuation and sterilizing gas input or pressurization steps for sterilization as through access  18 . Generally, V 3 &gt;&gt;(V 1 +V 2 ) and a wide range of ratios between V 1  and V 2  is acceptable when the transport capacity of accesses  34  and  36  are of the same or nearly the same vapor transporting capacity provided that one is larger than the other. The higher the ratio, the greater will be the transient pressure gradient allowing the selection of an optimum ratio for a particular application, pumping rate, etc. However, the smaller chamber should still be greater than the total internal volume of the lumens to be sterilized. Typically, the desired ratio between V 1  and V 2  is from about 2:1 to about 20:1; however, lower or higher ratios may be employed if desired.  
         [47]    47. Both compartments  12  and  14  may alternatively be connected via a conduit arrangement attached at  34 ,  36  (not shown) to a common source of sterilizing vapor and a common evacuating system in a well known manner. In addition, the connecting vapor-permeable accesses may be unequal in vapor transmission capacity to thereby produce a difference in effective rates of pressurization and evacuation for the two chambers. In this variation, the two compartments  12  and  14  may be equal or unequal in volume. Also, only one access need be used in one embodiment where the system interfaces through only one chamber. This represents one version of a single access system and can be accomplished by closing one port or vapor permeable access  34 ,  36 . The vapor passing or transmitting capacity of the areas  34 ,  36  may be varied by adjusting size, permeability or both and that may be combined with sizing the compartments  12  and  14  to produce any conceivable combination. The rate of change of the external pressure in the main chamber represented by  16  or V 3  can also be varied.  
         [48]    48.FIG. 2 illustrates a single access configuration in which a first chamber V 5  is entirely contained within a second V 6  and the lumen of interest V 4  extends between V 5  and V 6 . It will be recognized that this is similar to removing either V 1  or V 2  in FIG. 1 and sealing the remaining access to the outside  34  or  36  such that the function of the remaining chamber (V 1  or V 2 ) is assumed by V 3  which, of course, preserves the general principle of FIG. 1. An elongated tube generally at  40 , shown broken at  42 , illustrates an elongated internal lumen at  44  which encloses or contains a total volume denoted as V 4 . A hollow cap or bulb  46 , having an internal volume V 5 , is shown attached to the tube  40  using a gas permeable collar  48 . This assures sterilization of the entire device. This system is further enclosed in a chamber or package shown transparent and broken at  50  which has an internal volume represented by V 6 . Both end accesses  52  and  54  of the tube  10  are open so that a free flow between V 5  and ambient through V 4  may be established, together with flow penetrating the collar  48 . The relative sizes of V 4  and V 5  are without restriction except that, to promote timely sterilization, V 5            V 4 . A preferred range of ratios between V 5  and V 4  is from approximately 1 to 10 with a most preferred range of about 2-4. Of course, normally V 6 &gt;&gt;V 5 +V 4 . This will depend on the nature of the device to be processed.  
         [49]    49. In this embodiment, the entire assembly including the attached cap or bulb is designed to be subjected to sterilization in a common package represented by chamber  50 , which may be placed in a sterilization chamber as at  16  in FIG. 1. The package  50  is shown having a permeable access  56  and an internal volume V 6 . Of course, the ratio of V 5  to V 4  designed for a particular sterilant or sterilization process, such that cycling of the pressure in V 6  produces sufficient reversible flow through the opening  52  to enable the entire volume V 4  to be purged quickly in both directions by the actual or net flow in and out of V 5 .  
         [50]    50. In operation, the sterilization chamber containing the device of FIG. 2, including dimensionally stable flow-through container  50  is, in turn, placed in a conventional sterilization chamber (not shown), made accessible to a vacuum system and a pressurization system through the access represented by  56  which may be similar in configuration to  34 ,  36  of FIG. 1. The volume V 6  is first evacuated to a desired pressure below atmospheric causing outward flow to equalization. Thereafter, sterilant gas with or without a carrier gas, as desired, is introduced into the chamber  50  and, as the pressure in V 6  increases, an amount of this flows inward through the opening  52 , through lumen  44  and through the opening  54  into V 5 . This amount exceeds the volume V 4  so that complete purging and contact with the entire internal surface of the lumen  44  by the sterilizing gas is assured. These steps are cyclically repeated at desired timed intervals until sterilization is completed. After sterilization, the system may be subjected to one or more cycles using a purge gas such as N 2  to remove sterilant material.  
         [51]    51. An additional embodiment or configuration is illustrated in FIGS. 4 and 5 in which an endoscope device  60  with open-ended lumen  61  is sterilized in a storage package  62  that later is mounted to enable hanging storage in a straight configuration. In FIG. 4, the package  62  is shown protruding through an opening and partially deployed in a container  64  having a volume V 7 . Vapor permeable or gas transport areas in the wall of the package  62  are represented by  66  and  68  and an optional permeable area is shown in the otherwise sealed container  64  at  70 . The passage of the package  62  into the container  64  may be similar to the interchamber transition area illustrated in FIG. 3. The volume of the package may be represented by V 8 . The system including the container  64  and package  62  may be placed in a sterilization chamber  72  having a volume V 9  and an external connection as at  74  which is conventionally connected to a vacuum line and source of sterilant vapor or purge gas according to known techniques. In FIG. 5, the package  62  is shown mounted on a backing  80  for hanging on a hook as by using opening  82 .  
         [52]    52. It will be apparent from the above discussion that the system of FIG. 4 may be operated according to the method of FIG. 1 when optional transport area  70  is provided and according to the method associated with FIG. 2 without it. While the container  64  is represented as a cubic or box-like structure, it will be appreciated that it can be of any desired shape so long as it functions in the manner intended. This, of course, is also the case with respect to the hollow cap or bulb  46  of FIG. 2 and the cassette and lid combination of FIG. 1. Moreover, the opening in the container  64  may be in the form of a clamping device or any other confining mechanism that fits over one end of the package  62  to cause vapor material flowing between the package  62  and the container  64  to predominantly use the lumen  61 . Thus, for example, the chamber or container  64  may be a clamp-on envelope device.  
         [53]    53. Such an alternate container is shown at  90  in FIG. 6 which includes a spring clamp  92  connected to a semi-rigid structure  94 . The clamp  92  provides an opening  96  adapted to receive a tube as at  40  in FIG. 2 or a package as at  62  in FIG. 4 and may have a vapor transport permeable area as at  98 . The clamp  92  is operable to engage a tube or package for sterilization as needed.  
         [54]    54. In operation, the sterilization cycle for the embodiment illustrated in FIG. 1 begins with the evacuation of both chambers  12  and  14 . If the chambers are unequal in size, because of the difference in volume between the two chambers, the pressure in the smaller chamber volume initially decreases more rapidly than that of the larger one thereby producing a transient pressure gradient between the two chambers. This imbalance induces a net flow through the tube  28  from the larger chamber into the smaller chamber which continues until the pressure finally equalizes at the end of the evacuation portion of the sterilization cycle. In the next step, sterilant vapor is introduced into both chambers and a reverse imbalance occurs with the pressure rising faster in the smaller compartment than in the larger compartment thereby inducing a gradient which results in a flow through the tube  28  and collar  26  from the smaller chamber into the larger chamber until pressure equalization is again reached. Sterilization is accomplished by a series of cyclical alternate pressurization and evacuation steps, each resulting in a purging and replacement of the gas atmosphere within the tube  28 , thereby assuring complete sterilization of the inner surfaces of the tube. Of course, a similar effect can be produced by varying the vapor transport capacity of the ports  34 ,  36  accessing compartments. A higher capacity for vapor transmission produces the effect of making the chamber smaller. As above, a number of purge cycles may be used at the end of the process to remove traces of sterilant material from the cassette.  
         [55]    55. While the figures illustrate several embodiments, it should be kept in mind that many other possible configurations can be used which will enable the practice of the present invention. Thus, cassette  10  or package  62  may be replaced by peel pouch package for containing an endoscope, medical catheter or the like. In addition, the system can be configured to operate with separate vacuum pumps and pressurization devices attached at  34 ,  36  so long as these are properly controlled and coordinated in order to achieve a desired transient or time variable pressure gradient between the ends of the internal lumens of the device to be sterilized. These accommodations are considered well within the general knowledge of those skilled in the art.  
         [56]    56. As indicated above, an important aspect of the invention is the total sterilization of the device of interest and, in this regard, the passages or openings between the chambers as at  26  in FIG. 1, 48 in FIG. 2 and  76  in FIG. 4 are provided with gas or vapor permeable material at the interface with the device so that these areas remain exposed to the sterilant gas during the process. Thus, the passages  26  and  48  may be appropriately lined as at  27  in FIG. 3 using material that prevents direct cross flow between the chambers but one which is highly porous to allow penetration of the sterilant vapor through the layer  27  to the surface of the device as at  28 . A few porous openings are illustrated in FIG. 3 at  29 , but it will be appreciated that the entire surface of the device  28  will be adequately exposed to sterilant gas during the process. Alternatively, a low clearance fit of low leakage may also suffice.  
         [57]    57.FIGS. 7, 7A and  8  show another embodiment of containers systems for use in sterilizing endoscopes, catheters or other such devices in accordance with the invention in plastic trays which may be packages for shipping or even trays used for resterilization in the case of devices which are used more than once and require resterilization between uses. FIG. 7 depicts a fragmentary view of a part of a sterilization chamber  100  containing a port  102  which indicates intake and exhaust communication with a source of sterilant vapor and vacuum. A formed plastic tray is shown inside the sterilization chamber at  104  which in turn contains a breathing medical paper seal or other gas permeable area as indicated at  106  in which vapor exchange can take place with the atmosphere in the sterilization chamber  100 . A device to be sterilized in the form of an elongated lumen representation is shown at  108  mounted within the tray and connected at one end by insertion into a chamber  110  at  112 . The chamber  110  may be held in a recess in the tray  104  as part of the retention of the device in the tray, this may be a snap-fit relation. Optionally, a color chemical indicator  114  may be placed in the chamber  110  to indicate contact with the sterilant gas as a result of the sterilization process. The chamber  110  may be plastic or other material which will withstand a vacuum but which is sufficiently transparent so that the color indicator  114  can be recognized through the tray. The tray itself is also shown as a transparent device as is the sterilization chamber in the illustration, primarily to enhance clarity and understanding.  
         [58]    58.FIG. 7A is an enlarged view of the chamber  110  of FIG. 7 which can be fabricated from a plastic tube of a much larger diameter than that of the catheter or scope  108  to be sterilized. The chamber  110  is provided with a closed end  116  and the chemical sterilant indicator  114  may be located at or near that end  116 . Also shown are a second enclosure  118  and access opening  112 ; the chamber further describes an interior volume at  120  which, as has been previously described, should be greater than the volume of the lumen or lumens to be sterilized  108 .  
         [59]    59. As previously stated, the plastic tube or other member describing the generally cylindrical chamber  110  should be sufficiently strong to withstand a vacuum being pulled on the system without collapse and the end closings  116  and  118  may be an integral part of this system or be formed separately and joined by adhesive, screw or press fits but must be substantially gastight. The access port  112  is designed for a catheter or scope to be inserted through it into the chamber and so is preferably of a film material that is rather thin and elastic. The port hole should be designed to be undersized so that the catheter scope, as it is pushed through the hole, will force the hole to enlarge or stretch and the material will then form a substantially tight seal around the catheter or scope. As with previous embodiments, however, the film material must be of a composition that allows some limited leakage or permeation of gas so as to permit the system to sterilize the area of contact between the catheter, scope, etc., and the film. Thus, materials such as polyethylene film that is permeable by ethylene-oxide gas or an open-salved foam film should provide the necessary permeability.  
         [60]    60. The indicator dot  114  represents a chemistry that is affixed to the inside of the plastic chamber and can be viewed from the outside of the transparent plastic chamber and also through the plastic tray  104 . The indicator contains the necessary chemistry to indicate or record, by changing color, the adequate presence of sterilant gas in a concentration normally required to achieve sterility. This demonstrates that sterilant gas has passed through the entire length of the lumen  108  indicating that the device has been subjected to the sterilization procedure.  
         [61]    61.FIG. 8 depicts an embodiment similar to that of FIG. 7 but in which the formed plastic tray for containing the lumen-carrying device  120  is provided with an integral hollow chamber  122  molded as part of the tray and having an access port at  124  and a chemical sterility indicator at  126  within the integral hollow chamber. The criteria for the chamber  122  are the same as those for  110  of FIGS. 7 and 7A and so far as the sterilization process is concerned with the chamber being formed as a permanent part of the tray rather than a snap-in arrangement as shown in FIG. 7.  
         [62]    62.FIG. 9 shows yet another variation in which a gas permeable or breathable medical bag or custom peel pouch  130  contains a catheter or other lumen containing device  132  which extends through a seal opening  134  to a attached hollow chamber or tube  136  as previously described. In this embodiment the tube or chamber  136  is not entirely enclosed in the breathable medical bag or peel pouch  130  but protrudes partially into the sterilization chamber  100 . An optional chemical sterilization indicator is shown at  136 .  
         [63]    63.FIG. 10 is a view similar to FIG. 9 showing the plastic chamber as being contained entirely within the breathable medical bag or custom peel pouch  130 .  
         [64]    64. While the above description has emphasized elongated devices having a single open-ended lumen, multiple lumen devices such as vascular catheters having a plurality of parallel lumens or multi-lumen scoping devices can also be processed as a number of parallel elongate passages can be sterilized readily as well utilizing the techniques of the present invention. The relative volume relationships, of course, need reflect the total volume of the devices of interest. Additionally, it will be understood that a sterilization chamber may be used to simultaneously (concurrently) process a plurality of the illustrated or other devices in accordance with the invention. For example, the barrier  20  may be provided with a plurality of openings  39  to accommodate a plurality of tubular devices  26  or a plurality of cassettes or devices  10  can be provided in a batch to be sterilized in a common chamber.  
         [65]    65. This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the invention as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.