Patent Publication Number: US-9402929-B2

Title: Decontamination system including environmental control using a decontaminating substance

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 13/478,837, filed May 23, 2012, entitled “Decontamination System Including Environmental Control Using a Decontamination Substance,” which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application 61/490,813 entitled “Decontamination System Including Environmental Control Using a Decontaminating Substance,” which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to decontamination of medical devices. More particularly, the present invention relates to a system for decontaminating a medical device in a sterilization chamber with an environment at least partially controlled by the components of the decontaminating substance. 
     BACKGROUND 
     Robust medical equipment is often sterilized at high temperatures. Commonly, the equipment is sterilized in a steam autoclave under a combination of high temperature and pressure. While such sterilization methods are very effective for more durable medical instruments, advanced medical instruments formed of rubber and plastic components with adhesives are delicate and wholly unsuited to the high temperatures and pressures associated with a conventional steam autoclave. Steam autoclaves have also been modified to operate under low pressure cycling programs to increase the rate of steam penetration into the medical devices or associated packages of medical devices undergoing sterilization. Steam sterilization using gravity, high pressure or pre-vacuum create an environment where rapid changes in temperature can take place. In particular, highly complex instruments which are often formed and assembled with very precise dimensions, close assembly tolerances, and sensitive optical components, such as endoscopes, may be destroyed or have their useful lives severely curtailed by harsh sterilization methods employing high temperatures and high or low pressures. 
     Further, endoscopes in particular present problems in that such devices typically have numerous exterior crevices and interior lumens which can harbor microbes. The employment of a fast-acting yet gentler sterilization method is desirable for reprocessing sensitive instruments such as endoscopes. Other medical or dental instruments which comprise lumens, crevices, and the like are also in need of methods of cleaning and decontaminating which employ an effective reprocessing system which will minimize harm to sensitive components and materials. 
     SUMMARY 
     In one aspect, the present invention relates to a system for decontaminating a device. The system includes a decontamination chamber configured to retain the device and a chemical dispersion assembly configured to deliver a decontaminating fluid to the decontamination chamber. A pressure control assembly is connected to the decontamination chamber and configured to control the pressure in the decontamination chamber. The system also includes a system controller configured to control the decontamination chamber, chemical dispersion assembly, and pressure control assembly. A decontaminating fluid is added into the decontamination chamber at a first rate while increasing the pressure in the decontamination chamber. Adding the decontaminating fluid increases a relative humidity in the decontamination chamber. The decontaminating fluid is then added into the decontamination chamber at a second rate higher than the first rate while increasing the pressure in the decontamination chamber to about within a hold pressure range. After holding the decontaminating fluid in the decontamination chamber for a hold time within the hold pressure range, the decontaminating fluid is evacuated from the decontamination chamber in a decontaminating fluid evacuation step. The decontamination chamber is then vented to atmospheric pressure. 
     In another aspect, the present invention relates to a method for decontaminating a device in a decontamination chamber. A decontaminating fluid is added into the decontamination chamber at a first rate while increasing the pressure in the decontamination chamber. Adding the decontaminating fluid increases a relative humidity in the decontamination chamber. While increasing the pressure in the decontamination chamber to within a hold pressure range, the decontaminating fluid is added into the decontamination chamber at a second rate higher than the first rate. The decontaminating fluid is held in the decontamination chamber for a hold time within the hold pressure range, and the decontaminating fluid is subsequently evacuated from the decontamination chamber in a decontaminating fluid evacuation step. The decontamination chamber is then vented to atmospheric pressure. 
     While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an embodiment of a system for decontaminating a medical device. 
         FIG. 2  is a flow diagram of an exemplary process for decontaminating a medical device in the system of  FIG. 1 . 
         FIG. 3  is a graph of the relationship between pressure versus time during an exemplary decontamination cycle in the system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic view of an embodiment of a system  10  for decontaminating a medical, dental, or other device. The system  10  includes a system controller  12 , a decontamination chamber  14 , a pressure control assembly  16 , a chemical dispersion assembly  18 , and a vent valve  20 . The system controller  12  provides control signals to and/or receives control signals from components of the decontamination chamber  14 , pressure control assembly  16 , chemical dispersion assembly  18 , and vent valve  20 . In some embodiments, the system controller  12  is provided on the decontamination chamber  14  and is operatively connected to the components of the system  10 . The system controller  12  may include an interface (e.g., on the decontamination chamber  14 ) that allows a user of the system  10  to provide inputs and receive information regarding operation of the system  10 . For example, the system controller  12  may include an input device (e.g., a touch screen or keypad) that facilitates selection of decontamination cycle parameters by the user. 
     The decontamination chamber  14  is an enclosure that is fluidly connected to the pressure control assembly  16 , chemical dispersion assembly  18 , and vent valve  20 . The device to be decontaminated is placed into the decontamination chamber  16  by opening the door D and placing the medical device on a rack or other supporting assembly in the interior of the decontamination chamber  16 . When the door D is closed, the interior of the decontamination chamber  14  is sealed. The decontamination chamber  14  may include a temperature sensor  22  and a relative humidity sensor  24  configured to monitor environmental conditions in the decontamination chamber  14 . In some embodiments, the decontamination chamber  16  includes a fluid connection that is couplable to the device being decontaminated, or to a package that encloses the device being decontaminated. For example, the decontamination chamber  16  may connect to the device and/or package similar to the system described in U.S. patent application Ser. No. 12/959,535, which is incorporated herein by reference in its entirety. 
     The pressure control assembly  16  includes one or more vacuum pumps  30  configured to evacuate the decontamination chamber  14  to produce a vacuum or partial vacuum in the decontamination chamber  14 . In the embodiment shown, the pressure control assembly  16  includes two vacuum pumps  30 . A vacuum control valve  32  is disposed between the decontamination chamber  14  and the vacuum pumps  30  and is configured to control fluid communication between the decontamination chamber  14  and the vacuum pumps  30 . In an exemplary embodiment, the vacuum pumps  30  are configured to draw up to  300  liters per minute (L/min). A pressure transducer  31  may be operatively coupled to the decontamination chamber  14  to measure and monitor the pressure inside the decontamination chamber  14 . 
     To destroy or neutralize decontaminating substances that are drawn from the decontamination chamber  14  during operation of the system  10 , the pressure control assembly  16  includes one or more filters disposed between the vacuum control valve  32  and the vacuum pumps  30 . In the embodiment shown, the pressure control assembly  16  includes filters  34 ,  36 ,  38  disposed between the vacuum control valve  32  and vacuum pumps  30 . The type and number of filters employed in the pressure control assembly  16  may be a function of the type of decontaminating substance used in the system  10 . For example, in some embodiments, the decontaminating substance includes hydrogen peroxide (H 2 O 2 ), peracetic acid (PAA), and acetic acid. To neutralize this substance, the filter  34  may comprise potassium permanganate to remove the H 2 O 2  and PAA, the filter  36  may comprise a particulate filter to remove particulate matter generated by the filter  34 , and the filter  38  may comprise sodium bicarbonate to remove the acetic acid. In the embodiment shown, a filter  38  is associated with each vacuum pump  30 . At the exit of the filters  38 , the air drawn through the vacuum pumps  30  comprises oxygen (O 2 ) and carbon dioxide (CO 2 ). In some embodiments an exhaust filter  40  is connected to the outputs of each of the vacuum pumps  30 . 
     The chemical dispersion assembly  18  disperses a decontaminating substance in the decontamination chamber  14  during operation of the system  10 . The chemical dispersion assembly  18  includes a nozzle  50  connected to an air flow subassembly  52  and a chemical flow subassembly  54 . The air flow subassembly  52  includes an air flow control valve  60 , an air flow meter  62 , an air filter  64 , and an air pressure regulator  66 . The air pressure regulator  66  may include a source of pressurized air. In an exemplary implementation, the air pressure regulator  66  provides pressurized air at about 50 pounds per square inch (psi). Air flow to the nozzle  50  is controlled by the air flow control valve  60  and monitored by the air flow meter  62 . Air from the air pressure regulator  66  is filtered of impurities by the air filter  64 . 
     The chemical flow subassembly  54  includes a chemical flow control valve  70 , chemical flow meters  72 , and chemical reservoir  74 . Flow of a decontaminating fluid  76  from the chemical reservoir  74  to the nozzle  50  is controlled by the chemical flow control valve  70  and monitored by the chemical flow meters  72 . The decontaminating substance may be pushed or pulled from the chemical reservoir  74 . The chemical reservoir  74  may be a holding tank or other assembly configured to hold a decontaminating fluid  76 . In some embodiments, the decontaminating fluid  76  is a chemical or other substance suitable for use in a sterilization process that complies with the International Organization for Standardization (ISO) standard ISO/TC 198, Sterilization of Healthcare Products and/or the Association for the Advancement of Medical Instrumentation (AAMI) standard ANSI/AAMI/ISO 11140-1:2005, “Sterilization of Healthcare Products—Chemical Indicators—Part I: General Requirements” (Arlington, VA: AAMI 2005). In some embodiments, the decontaminating fluid  76  is a room temperature (e.g, 20° C. to 25° C.) substance that can be dispersed as an atomized/vaporized solution or fog during the decontamination process. For example, the decontaminating fluid  76  may include H 2 O 2 , PAA, and/or acetic acid. The decontaminating fluid  76  may also be comprised of water. In one exemplary implementation, the decontaminating fluid  76  is comprised of about 62% water. 
     In some embodiments, the nozzle  50  is an atomizing nozzle that is configured to transform the decontaminating fluid  76  at the input of the nozzle  50  to a atomized/vaporized solution at the output of the nozzle  50 . To produce the atomized/vaporized solution, the atomizing nozzle may generate fine droplets of the decontaminating fluid  76  that average, for example, less than about 10 μm in diameter or width. Droplets of this size tend to bounce off of solid surfaces, allowing for even dispersion, while avoiding excessive condensation, corrosion, and surface wetting issues in the decontamination chamber  14 . In addition, the small droplets evaporate, and the vapor penetrates normally inaccessible areas, resulting in a more effective process. In some embodiments, the droplets of decontaminating fluid  76  are 10 μm diameter droplets with an evaporation rate of 50-375 ms at between 0-75% RH. One example nozzle  50  that may be suitable for use in the system  10  is a nozzle such as that used in the Minncare Dry Fog® or Mini Dry Fog systems, sold by Mar Cor Purification, Skippack, Pa. Another example nozzle  50  that may be suitable for use in the system  10  is a spray nozzle assembly including Spraying Systems Co. product numbers 1/4J-316SS, SU1A-316SS, and 46138-16-316SS, sold by Spraying Systems Co., Wheaton, Ill. 
     The amount of atomized/vaporized solution generated by the chemical dispersion assembly  18  is controlled by the system controller  12  by controlling the rate and amount of the decontaminating fluid  76  that is forced through the nozzle  50 . The rate and amount of decontaminating fluid  76  that is forced through the nozzle  50  may be preprogrammed into the system controller  12  or may be manually entered into the system controller  12  by a user of the system  10 . In addition, the system controller  12  may include multiple programs that provide different rates and amounts of the decontaminating fluid  76  to the nozzle  50 . 
     In some embodiments, an atomizer purge valve  80  is connected between the air flow subassembly  52  and chemical flow subassembly  54 . The atomizer purge valve  80  provides a fluid connection between the air pressure regulator  66  and the chemical flow subassembly  54  input to the nozzle  50 . To purge decontaminating substance from the nozzle  50 , the air control valve  60  and chemical control valve  70  are closed and the atomizer purge valve  80  is opened to allow pressurized air from the air pressure regulator  66  to be provided through the chemical input of the nozzle  50 , thereby forcing residual decontaminating substance out of the nozzle  50 . 
     The vent valve  20  allows air to be drawn into the decontamination chamber  14  during venting steps of the decontamination cycle. For example, if the pressure in the decontamination chamber  14  is below atmospheric pressure, the vent valve  20  may be opened to raise the pressure in the decontamination chamber  14 . An air filter  84  is disposed along the intake to the vent valve  20  to remove contaminants from the air stream flowing into the decontamination chamber  14  during venting. 
     As discussed above, the system controller  12  operates the components of the system  10  to decontaminate a device or article in the decontamination chamber  14 . The system controller  12  may include one or more selectable preprogrammed decontamination cycles that are a function of the device characteristics and desired level of decontamination. Alternatively, cycle parameters may be input into the system controller  12  by a user. As a part of the decontamination cycle, the system controller  12  may monitor and control the environment within the decontamination chamber  14  to improve the efficacy of the decontamination process. For example, the temperature, relative humidity, and pressure within the decontamination chamber  14  may be monitored via the temperature sensor  22 , relative humidity sensor  24 , and pressure sensor  31 , respectively, that are operatively connected to the decontamination chamber  14 . The system  10  may include a temperature control element (not shown) associated with the decontamination chamber  14  to control the temperature in the decontamination chamber  14 . The pressure within the decontamination chamber  14  is controllable with the vacuum pumps  30 , air pressure regulator  66 , and vent valve  20 . 
       FIG. 2  is a flow diagram of an embodiment of a process for decontaminating a device in the system  10  of  FIG. 1 . Prior to initiating the process, the device to be decontaminated may be preconditioned to allow the device to reach ambient temperature. In some embodiments, the ambient temperature is less than about 30° C., and more specifically between about 18° C. and about 30° C. The preconditioning of the device to ambient temperature improves the efficacy of the decontamination process of the system  10 . The device to be decontaminated is placed inside the decontamination chamber  14 , and the door D is closed to seal the interior of the decontamination chamber  14 . In some embodiments, the relative humidity in the decontamination chamber  14  is preconditioned to less than about 50% relative humidity. The preconditioned relative humidity may be ambient relative humidity, or the conditions inside the decontamination chamber  14  may be adjusted to reach the preferred preconditioned relative humidity. The user may then initiate a decontamination cycle using the system controller  12 . 
     In step  100 , the pressure in the decontamination chamber is reduced to within a sub-atmospheric pressure range in a first evacuation step. For example, the pressure control assembly  16  may evacuate the decontamination chamber  14  to produce a vacuum or partial vacuum in the decontamination chamber  14 . In some embodiments, the pressure in the decontamination chamber  16  is reduced to less than  10  ton. 
     After the pressure in the decontamination chamber  14  reaches the programmed sub-atmospheric pressure, the chemical dispersion assembly  18 , in step  102 , adds the decontaminating fluid  76  into the decontamination chamber  14  at a first rate. For example, the chemical dispersion assembly  18  may disperse or inject the decontaminating fluid  76  into the decontamination chamber  14 . According to various embodiments, the first rate is selected such that the water content of the decontaminating fluid  76  increases the relative humidity and pressure in the decontamination chamber  14 . As discussed above, the efficacy of the decontaminating fluid  76  may improve with higher relative humidity. In some embodiments, the decontaminating fluid  76  is dispersed at the first rate until the relative humidity is in the range of about 50% to about 90%. The relative humidity target is based on maximization of efficacy of the components of the decontaminating fluid  76 . 
     While dispersing the decontaminating fluid  76 , the pressure in the decontamination chamber  14  is increased. The pressure increase may be effected by the air pressure regulator  66  of the chemical dispersion assembly  18 . That is, the air pressure that is employed to force the decontaminating fluid  76  through the nozzle  50  may be used to increase the pressure in the decontamination chamber  14 . Alternatively, the pressure increase may be produced, at least in part, by opening the vent valve  20 . 
     After the relative humidity in the decontamination chamber  14  reaches a preferred level, in step  104 , the decontaminating fluid  76  is added into the decontamination chamber  14  at a second rate. In some embodiments, the second rate is higher than the first rate of step  102 . The duration of adding at the second rate is set such that the concentration or density of the decontaminating fluid  76  reaches predetermined levels inside the decontamination chamber  14  at the end of dispersion at the second rate. The predetermined concentration of the decontaminating fluid  76  may be set in the decontamination cycle selected or programmed by the user on the system controller  12 , and may be a function of the preferred or required level of decontamination of the device. The introduction of the decontaminating fluid  76  through the nozzle  50  with air flow subassembly  52  provides good circulation and coverage of the decontaminating fluid  76  within the decontamination chamber  14 . 
     While the decontaminating fluid  76  is dispersed at the second rate, the pressure inside the decontamination chamber  14  is increased. Again, the pressure increase may be effected by the air pressure regulator  66  of the chemical dispersion assembly  18 . Alternatively, the pressure increase may be produced, at least in part, by opening the vent valve  20 . After adding the decontaminating fluid  76  at the second rate for a duration to produce the programmed level of concentration, the pressure inside the decontamination chamber  14  is within a hold pressure range. In some embodiments, the hold pressure is between about 1 and 760 torr. In a preferred embodiment, the hold pressure is about 500 torr. 
     In step  106 , when the decontamination chamber  14  is within the hold pressure range, the conditions inside the decontamination chamber  14  are maintained for a hold time. The decontaminating fluid  76  is held in the decontamination chamber  14  for an amount of time sufficient to decontaminate the medical device disposed therein. This amount of time may be programmed into the system controller  12 , and may be based on the size and type of medical device being decontaminated, as well as the content and concentration of the decontaminating fluid  76 . 
     When the decontaminating fluid  76  has been held in the decontamination chamber  14  for the desired or programmed amount of time, in step  108 , the system controller  12  commands the pressure control assembly  16  to again evacuate the decontamination chamber  14  to reduce the pressure in the decontamination chamber  14  to within a sub-atmospheric pressure range in a second evacuation step. The reduction in pressure draws the environment in the decontamination chamber  14  through the filters  34 ,  36 ,  38  and removes the decontaminating fluid  76  from the decontamination chamber  14 . In some embodiments, the pressure in the decontamination chamber  14  is reduced to less than  10  ton. In some embodiments, the decontamination chamber  14  is maintained at the reduced pressure for a programmed period of time. 
     The steps of adding the decontaminating fluid  76  into the decontamination chamber  14  and/or evacuating the decontamination chamber  14  may be performed a plurality of times. For example, after the decontaminating fluid  76  is evacuated from the decontamination chamber  14  in a first cycle as described above, the decontaminating fluid  76  may be added into the decontamination chamber again in a second cycle. The decontaminating fluid  76  from the second cycle may then be held in the decontamination chamber  14  for a hold time (similar to step  106  described above). The decontamination chamber  14  may subsequently be evacuated to remove the decontaminating fluid  76 , as described above in step  108 . The system controller  12  may be programmed to repeat the decontamination cycle any number of times. 
     In addition, after any iteration of the second evacuation step, the system  10  may be programmed to increase the pressure in the decontamination chamber  14  without adding decontaminating fluid  76  into the chamber. For example, in some embodiments, the chemical flow control valve  70  is closed and the air flow control valve  60  is opened to force air into the decontamination chamber  14  to increase pressure. As another example, the vent valve  20  is opened to raise the pressure inside the decontamination chamber  14 . After the pressure in the decontamination chamber  14  reaches a desired level (e.g., atmospheric pressure), the decontamination chamber  14  is again evacuated to a sub-atmospheric pressure. The additional steps of increasing pressure in the decontamination chamber  14  followed by evacuation may be employed to assure complete removal of the decontaminating fluid  76  from the decontamination chamber  14 . 
     After the programmed number of cycles or evacuation steps, in step  110 , the system controller  12  may open the vent valve  20  to vent the decontamination chamber  14  to atmospheric pressure. This draws air exterior to the decontamination chamber  14  through the air filter  84  and into the decontamination chamber  14 . When the pressure in the decontamination chamber  14  equalizes with the pressure exterior of the decontamination chamber  14 , the decontamination chamber  14  may be opened to remove the decontaminated device from the system  10 . 
       FIG. 3  is a graph of pressure versus time in an exemplary decontamination cycle. The graph in  FIG. 3  illustrates the pressure conditions of the cycle after the device and decontamination chamber  14  have been preconditioned as described above. At time  120 , the decontamination chamber  14  is evacuated to a sub-atmospheric pressure in a first evacuation step. In the embodiment shown, the sub-atmospheric pressure is approximately  10  ton. When the programmed sub-atmospheric pressure is reached in the decontamination chamber  14 , at time  122 , adding the decontaminating fluid  76  as described above in steps  102  and  104  occurs. After adding the decontaminating fluid  76  at the second rate as described in step  104 , the decontamination chamber  14  is at the hold pressure at time  124 . In the embodiment shown, the hold pressure is approximately  500  torr. The conditions in the decontamination chamber  14  are held constant for a hold time until time  126 . In some embodiments, the hold time between times  124  and  126  is in the range of approximately five minutes to five hours. After the hold time, the decontamination chamber  14  is evacuated to a sub-atmospheric pressure in a second evacuation step. In the embodiment shown, the sub-atmospheric pressure is approximately  10  torr. When the programmed sub-atmospheric pressure is reached in the decontamination chamber  14 , at time  128 , the pressure is raised in decontamination chamber  14 . In some embodiments, the pressure in the decontamination chamber is raised to approximately atmospheric pressure. After the programmed pressure is reached in the decontamination chamber  14 , at time  130  the decontamination chamber  14  may again be evacuated to a sub-atmospheric pressure (e.g., 10 torr), and subsequently vented to atmospheric pressure at time  132 . The additional evacuation step starting at time  130  is optional, and may be employed to assure complete removal of the decontaminating fluid  76  from the decontamination chamber  14 . 
     Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.