Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
  • A61L2/16—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using chemical substances
  • A61L2/20—Gaseous substances, e.g. vapours
  • A61L2/202—Ozone
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
  • A61L2/02—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using physical phenomena
  • A61L2/14—Plasma, i.e. ionised gases
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
  • A61L2/24—Apparatus using programmed or automatic operation
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
  • A61B1/12—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with cooling or rinsing arrangements
  • A61B1/121—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with cooling or rinsing arrangements provided with means for cleaning post-use

Definitions

• the present invention relates to the general field of sterilization of objects and surfaces of any kind and any shape and it relates more particularly to a process and various devices for plasma sterilization operating at room temperature and at atmospheric pressure.
• PRIOR ART Sterilization corresponds to a very precise level of quality in the medical and food industries. In the medical environment, it designates a destruction of all microorganisms whatever their nature. According to the European Pharmacopoeia, an object can be considered sterile if the probability that a viable micro-organism is present is less than or equal to 10 "5.
• the sterilization time is the time necessary to sterilize an object" normally contaminated " , that is to say containing 10 6 bacterial spores.
• the sterilization of an object corresponds to a reduction in the initial population of bacterial spores present on this object from 10 6 spores to 10 "6 spores is a logarithmic reduction 12 decades.
• the time required to reduce a decade is by definition called decimal reduction time, denoted D. It is a fundamental variable characterizing a sterilization process.
• the sterile state of an object must be maintained by a specific packaging which must be compatible with the sterilization method used (permeable to the sterilizing agent) and prevent penetration of microorganisms during the transport and storage phases, in order to guarantee the sterility of the instrument during its next use.
• the autoclave which relies on the action of moist heat at high temperature (at least 121 ° C), is the most efficient and cheapest process to use, but it does not allow sterilization of heat-sensitive devices increasingly present, especially in the medical field.
• Gas sterilization processes (ethylene oxide, formaldehyde, hydrogen peroxide) use the biocidal nature of a gas placed in a sterilization enclosure and allow low-temperature sterilization of heat-sensitive devices.
• they have many drawbacks: the toxicity of the gases considered, which imposes complex procedures for use and control; the obligation, in certain cases (with plastic materials for example), to carry out a phase of desorption of the toxic gas after the sterilization phase; finally the length of the treatment which often requires several hours.
• the limited killing effect on certain bacterial spores (such as Bacillus stearothermophilus spores) should be noted.
• Low pressure plasma sterilization processes are also known which optionally make it possible to combine the sterilizing effects of biocidal gas at low pressure with the formation, in a plasma, from a biocidal gas mixture such as H2O2 or a non-gas mixture.
• biocide in general simply O 2 , H 2 , H 2 O, N2 or a rare gas such as Argon
• reactive species creation of 0 ° and OH ° radicals ionized and / or excited species.
• Low pressure plasmas include, in the majority of cases, microwave or radiofrequency plasmas.
• Sterilization by low pressure plasma can be very effective in the space where the plasma is created (inter-electrode space), but, apart from the fact that the sterilization zone is then very small (about a few cm in height), the characteristics of the plasma depend very strongly on the dielectric constant, the nature and the size of the object to be sterilized. In this case, the plasma prevents a truly uniform treatment over the entire surface and has a highly corrosive action on the objects to be sterilized.
• Another known method using the post-discharge principle consists in carrying out an ozone treatment at atmospheric pressure using an appropriate device called an "ozonator".
• This treatment is similar to a sterilization by plasma in post-discharge at atmospheric pressure whose carrier gas does not contain moisture to promote the creation of ozone contains oxygen.
• the biocidal action of ozone which is mainly used for the disinfection of water and gas waste, is quite limited in terms of sterilization.
• the separation between the plasma production zone and the treatment zone limits the efficiency of the process because only the medium and long-lived species are still active at the level of the object.
• these species being less reactive than those with a short lifespan, it is necessary to increase their concentration and the treatment time.
• the second phase Ph2 starts when the humidity level in the enclosure is sufficient and corresponds to the sterilization phase proper from a plasma discharge creating species having a sporicidal action.
• the duration of this phase is fixed by the desired level of decontamination.
• the last phase Ph3 corresponds to the rinsing of the enclosure which marks the end of the treatment cycle.
• the effectiveness of this post-discharge process is based on the possibility of propagating the active species created by the plasma source to the surface to be sterilized.
• the propagation of the species from one point to another of the enclosure involves both the effective propagation time and the surfaces encountered between the two points.
• both of these two solutions have the consequence of significantly increasing the cost of the treatment enclosure by imposing in particular a high voltage connection between the different plasma sources or a complex geometry for the enclosure.
• the object of the present invention is therefore to propose an improved sterilization process making it possible to optimize the sterilization time for all configurations, including for large volume enclosures or elongated objects without increasing the cost of the pregnant.
• An object of the invention is also to propose an improved process making it possible to reduce the number of plasma sources necessary for sterilization without making the manufacture of the enclosure more complex.
• Another object of the invention is to propose a method presenting a sporicidal efficacy in reasonable time at low temperature.
• Yet another object is to propose a non-polluting process avoiding any manipulation of dangerous products unlike the simplest methods known for sterilization at low temperature.
• a method of sterilization by plasma in the presence of moisture from a non-biocidal gas containing oxygen and nitrogen of at least one object placed outside the discharge in a sealed treatment enclosure subjected substantially to atmospheric pressure characterized in that it comprises the following stages:
• the end of the rinsing step is detected by crossing a minimum threshold of a parameter.
• this parameter is the relative humidity and the ozone concentration measured by a multi-parameter sensor placed at the outlet of the treatment enclosure.
• the plasma discharge A and the introduction of humidity are simultaneous and the discharges of the first and second plasmas overlap so that the creation of the second plasma B begins before that of the first plasma A.
• the discharges of the first and second plasmas can use the same plasma source.
• the discharges of the first and second plasmas are different in nature to allow separate optimization of each phase.
• the flow rate of the non-biocidal gas is different between the different phases.
• the choice of discharge regimes for the first and second plasmas is determined by the elementary pattern of the voltage signal (alternating, damped or continuous alternating), the frequency of repetition of the pattern and the total setpoint current.
• the detection of the peak current makes it possible to control the speed used. Preferably, this detection is done with a bandwidth of the order of the frequency between the pulses.
• the repetition frequency of the patterns or a lag time between the elementary patterns is used to limit the rise in temperature in the reactor while maintaining the same discharge regime.
• the increase in temperature of the object is compensated for by the thermalization of an evaporative humidifier at a temperature slightly lower than that of this object.
• this compensation is obtained by controlling the effectiveness of a vaporizer so as to keep the humidity constant at the level of the object.
• the high voltage supply is produced from a low voltage supply drawn from a transformer used as a filter and as a voltage booster.
• controlling the repetition of the low voltage pulses makes it possible to introduce an adjustable latency time.
• the repetition frequency of the low-voltage pulses is lower than the resonant frequency of the transformer.
• the repetition frequency of the pulses is equal to the resonant frequency of the transformer.
• the supply is regulated on the basis of a measurement of a current, preferably direct for a supply of direct voltage, synchronous for a supply of alternating voltage, measurement carried out through a resistor.
• Current can also be measured indirectly by measuring the charge of a capacitor. In the case of a DC voltage supply, the discharge of the capacitor is ensured by periodic earthing.
• the power supply is regulated on the basis of a peak current measurement.
• the signal used for regulation is smoothed with a time constant greater than 100 ms, preferably 1 s.
• the electrodes are produced from a blade comprising one or more points placed parallel to a flat or cylindrical surface serving as a counter-electrode.
• the number of tips is chosen so as to facilitate the use of the different discharge regimes desired during the treatment.
• the device comprises several treatment chambers, each treatment chamber comprising at least one plasma production zone connected in a fixed manner to at least one sterilization zone, the production zones of plasma being connected to a common central unit containing at least the first source of non-biocidal gas, the humidification chamber, the system for recovering gaseous residues and as many high-voltage power supplies as there are outputs allowing the speakers to be treated simultaneously by applying different discharge regimes.
• the sterilization area is slightly pressurized to allow flow into fine capillaries.
• It includes a multi-parameter sensor for each connection channel allowing the composition of the gas leaving an enclosure to be checked before filtration.
• FIGS. 1a, 1b and the are chronograms illustrating the improved plasma sterilization method according to the invention
• FIG. 2 is a block diagram of a plasma sterilization device according to the invention
• FIG. 3 is a block diagram of a high voltage power supply adapted to the device of FIG. 2
• FIG. 4 illustrates an exemplary embodiment of the plasma sterilization device of FIG. 1,
• FIG. 5 shows an exemplary embodiment of a treatment enclosure in accordance with FIG. 1,
• FIG. 5a is an exploded view of FIG. 5 illustrating a particular configuration of the discharge zone
• FIG. 6 is a timing diagram of the different stages of a plasma sterilization process of the prior art.
• the invention relates to an improved sterilization method having a sporicidal efficacy tested in particular on bacterial spores considered by the European Pharmacopoeia as the most resistant: Bacillus subtilis and Bacillus stearothermophihis.
• this process uses a gaseous mixture containing oxygen and nitrogen from which a low temperature plasma is created, the chemical species of which have a sterilizing action on the object to be treated in the presence of moisture. .
• the object to be treated is placed outside the space where the discharge takes place and the treatment is carried out at atmospheric pressure.
• Plasma is a gas partially activated by an electromagnetic source of sufficient energy.
• the species created in the plasma are ionized (molecules or atoms), neutral (such as radicals) or excited species. These gaseous species have an increased reactivity which allows them to interact with the surfaces of the object or objects to be sterilized and thus to destroy the microorganisms present on these surfaces.
• FIG. la to le A preferred example of a treatment cycle in accordance with the invention is illustrated in Figures la to le.
• This cycle is always broken down into three successive phases, but these phases are now organized differently with: a first phase Pha of bringing the chamber into equilibrium comprising a discharge of a first plasma A, a second phase Phb of treatment workforce comprising a discharge of a second plasma B and a third and final rinsing phase Phc.
• the reduction in the total cycle time involves optimizing each of these three phases, taking into account its effect, in particular on the possibly next phase.
• the objective of the first phase Pha is to bring the entire enclosure under conditions allowing the species that will be created during the next phase Phb to spread over all of the surfaces to be treated and to have an action sporicide in reasonable time. It includes, as in the aforementioned process, necessarily the homogeneous introduction of moisture which is a minimum condition necessary for the creation of species during the second Phb phase. However, it also comprises a concomitant discharge or not of a first plasma not necessarily having a significant sporicidal action but essential to ensure the equilibrium of the enclosure before the start of the next phase. A simultaneous start of the first plasma and the introduction of humidity also makes it possible to significantly reduce the total treatment time as illustrated in FIG. 1b. The duration of this phase is determined according to the volume of the enclosure and the objects to be sterilized.
• Table 1 TO stabilization time before sterilization (excluding humidity) in a tube with an internal diameter of 25 mm
• the second Phb phase is the effective treatment phase, lasting 12 D in the case of sterilization. D is measured from tests carried out for the most unfavorable conditions on the microorganisms considered to be the most resistant.
• the second plasma is optimized to have maximum sporicidal action by limiting the degradation of materials. If the gas production means allow, this second phase Phb can be advanced and therefore begin before the end of the first phase Pha, as illustrated in FIG. Le, in order to guarantee optimal filling of the plasma B before l plasma stop A. In this configuration, the second phase Phb then has a duration greater than 12D.
• the last phase must allow the enclosure to return to an atmosphere compatible with the storage of the enclosure and its subsequent opening by circulation of the non-humidified gas.
• FIG. 2 A block diagram of a plasma sterilization device implementing the improved method according to the invention is illustrated in FIG. 2.
• This device is organized around a treatment enclosure 10 separated into two zones: a production zone plasma 10a inside which, by a discharge between two electrodes, is created a plasma and a sterilization zone 10b where the object to be treated is placed.
• the discharge is produced from a non-biocidal gas mixture supplied by a gas source 12 via a humidification chamber 14.
• the humidification chamber has at least two channels, one at maximum humidity and one at minimum humidity. , known as the dry process.
• the choice between the two routes is made according to the current phase: wet route during the Phb phase and at least part of the Pha phase, dry route during the Phc phase.
• This treatment enclosure is completely closed.
• the gas mixture contains oxygen and nitrogen and its composition may vary depending on the nature of the object to be sterilized.
• the level of oxygen contained in the mixture depends on the aggressiveness of the mixture vis-à-vis the materials of the objects to be sterilized.
• the gas mixture must contain at least 10% oxygen and 10% nitrogen to ensure an acceptable sporicidal effect as shown in the following table (the samples contain bacterial spores of subtle Bacillus / s):
• Table 2 comparison of the efficiency of a discharge from a carrier gas containing argon and nitrogen and associated ozone measurement (T means sample at the control level).
• this mixture can be ambient air obtained from a compressor.
• the relative humidity level in the sterilization zone during the second Phb phase is between 50% and 100%, advantageously greater than or equal to 70%.
• Table 3 shows the importance of this parameter:
• Table 3 comparison of the efficiency at an identical time for a RH of 20% to 80%.
• the flow of entry of the gas mixture into the treatment chamber 10 is adjusted as a function of the size and the quantity of the objects to be sterilized and of the phase in progress, by a control device (for example a valve 16) disposed at the outlet of the gas source 12 and allowing control of its flow speed and its concentration.
• a control device for example a valve 16
• the object to be sterilized 20 is placed on a support, which must allow the circulation of the sterilizing agent over its entire surface, in the sterilization zone 10b, that is to say outside the plasma production zone. (inter-electrode zone of creation of the discharge).
• the supply is made by a wet gas mixture and the plasma production zone comprises on the one hand an inlet orifice for the arrival of the carrier gas and on the other hand two electrodes, an electrode high voltage 24 supplied by a low frequency high voltage generator 26 and a ground electrode 28, intended to produce between them an electric discharge known as a "crown" discharge.
• the corona discharge is characterized by the use of two electrodes having a very different radius of curvature. The increase in the electric field near the electrode with a small radius of curvature makes it possible to decrease the voltage necessary for the appearance of the discharge while using a voltage supply which can be low frequency since it does not use the effect of resonance at the electrodes.
• the orifice for the arrival of the carrier gas 30 is preferably located near the electrodes 24 and 28 to optimize its passage through the inter-electrode space, the production of the plasma being located in this inter-electrode space.
• a gas outlet orifice 32 is located in turn in the sterilization zone 10b downstream of the object to be treated with respect to the natural direction of flow of the gas.
• a humidity and temperature sensor 40 is placed at the outlet of the humidifier to check the quantity of water vapor present in the gas at the inlet of the discharge zone 10a.
• a bacteriological filter 42 is placed between the sensor and the inlet 30 to guarantee the sterility of the injected gas, in particular during the last Phc rinsing phase.
• the gaseous residues (effluents) resulting from the discharge are evacuated by the outlet 32 to a recovery system 22 so as not to exceed the limit concentrations fixed by the regulations.
• a recovery system 22 so as not to exceed the limit concentrations fixed by the regulations.
• the gas leaving the recovery system 22 is analyzed, for example with an ozone sensor 44 to verify the proper functioning of the filtering before discharge to the outside.
• a multi-parameter sensor 46 is placed before the filter 42 to analyze the gas leaving the reactor 10.
• this sensor is sensitive to the temperature, humidity and the chemical composition of the gas, for example in ozone.
• the measurements coming from the sensors 40, 44 and 46 and from the source 26 are centralized towards a control member 50 which controls the passage between the different phases of the cycle by changing the setpoints sent to the high voltage source 26, the valve 16 and l humidifier 14.
• the first and second phases of plasma creation having a different role: balancing for the first plasma by creating the chemical conditions favorable to sterilization, sporicidal effect for the second plasma, it is preferable to be able to have different types of discharge regimes corresponding to different chemical productions in order to optimize the process. To obtain these different regimes, it is possible to use different plasma sources.
• the general objective of the various solutions proposed below is to increase the number of discharge regimes achievable from a given configuration to allow maximum optimization of the process and the means enabling their control. For example, for a given type of high voltage signal defined by its polarity, its shape and its frequency, the signal associated with given electrodes, the discharge regime and the production of chemical species depend on the intensity and the shape current.
• the total current measured on the ground electrode contains different components associated with different physical effects.
• a positive DC voltage associated with a tip-plane type geometry
• the current is, below a voltage threshold, composed only of a DC component attributed to a so-called "glow" regime.
• a so-called pulse current composed of pulses of high amplitude, typically a few milliamps and of short duration, typically 100 ns, associated with the regime known as “streamers”.
• a higher voltage gives rise to a direct current of electric arc corresponding to the appearance of a conductive channel in the gas.
• DBD Dielectric Barrier Discharge
• Intermediate energy regimes then appear which make it possible to cross different zones of chemical production.
• New pulses then appear of very high amplitude, typically a few hundred milliamps and of short duration, typically 100 ns.
• This type of DBD discharge therefore offers greater flexibility in choosing the type of diet.
• the production of chemical species by the plasma strongly depends on the presence of the impulse current.
• the amount of charge associated with the pulse current is of the same order of magnitude as the amount of charge associated with the direct current.
• the amount of charge associated with the synchronous current can remain much greater than the amount of charge coming from the pulses, particularly in the low power regimes used for the process discussed.
• the effective impedance of the discharge giving the relationship between current and voltage can change over time and is highly dependent of the geometry of the electrodes.
• the regulation of the high voltage supply is therefore preferably done at constant current to maintain the same discharge regime and the same production of chemical species in order to ensure a constant sterilizing effect.
• the discharge regime and the production of chemical species are a function of the current per unit length.
• the peak current as a minimum as a control measure, at best as a regulation parameter.
• a control measurement can be carried out by counting for a given period the number of impulse discharges detectable by current peaks of a few milliamps and of short duration (typically 100 ns), the density over time of these current peaks serving determining the regime used.
• the measurement system must be fast and precise enough to give the exact number of discharges.
• the voltage signal applied to the high voltage electrode can be continuous or in slots, of positive or negative sign, alternating or even pulsed depending on the discharge regime chosen for each of the phases. It is therefore preferable for the generator to have a solution offering maximum modularity in terms of amplitude and shape.
• the generator can be produced as described in FIG. 3.
• a transformer 100 having a resonant frequency located in the low frequencies, typically less than 100 kHz, is supplied by a low-voltage DC source 102 operating from preferably as a current source via a transistor used as a controlled switch 104.
• the duration of the pulse 106 is adjusted so as to optimize the breaking current, the transformer serving both as a voltage step-up element and as a filter and providing a elementary sinusoidal pattern.
• the repetition frequency of the well is determined by the well generator 114 according to the instruction supplied by the control member 50. By repeating this well at the resonant frequency of the transformer, a quasi-sinusoidal signal 108 is obtained.
• a pulsed supply is obtained with an elementary pattern comprising a damped sinusoid 110.
• a DC voltage supply it is necessary to place a rectifier system at the transformer output. It is also possible in all cases of continuous, sinusoidal or damped sinusoidal pattern to introduce a lag time between the patterns corresponding to a zero voltage at the transformer output to obtain a signal comprising an envelope of rectangular type, for example of type 112 for a sinusoidal pattern.
• the amplitude of the signal depends on the value of the DC voltage applied to the transformer.
• the regulation can be carried out on the basis of a current or voltage measurement at 118, the comparison of which with a setpoint inside a comparator 116 makes it possible to act on the low voltage source 102.
• the simplest configuration for obtaining a crown discharge is a configuration known as point-plane in which the set of electrodes is composed by a point placed perpendicular to a plane.
• This configuration makes it possible to determine a relationship between current and electric field characterizing the different discharge regimes.
• By extension of a tip-yaw configuration it is possible to multiply the number of tips by placing them on the same blade parallel to the plane.
• For a discharge regime defined from the tip-plane configuration it is thus possible to increase the total current at constant voltage without changing the regime by increasing the number of tips.
• This increase in current at constant discharge and constant voltage is possible as long as the tips are electrically independent, that is to say as long as their separation distance remains greater than 2d, d being the inter-electrode distance. Beyond this density, the total current saturates at constant electric field.
• Table 4 Effect of the number of points on the maximum current before going to arc for an inter-electrode distance of 10 mm.
• transition to the arc poses stability problems, increases the problems of electromagnetic compatibility and mechanical resistance of the electrodes and that this therefore corresponds to a regime more difficult to use.
• the increase in the density of the tips therefore makes it possible to extend the voltage ranges corresponding to each discharge regime.
• This increase in the operating range corresponds to an increase in the stability of each regime, which reduces the constraints on regulation.
• the density limit is given by the manufacturing constraints linked to the electrode and by the maximum voltage that can be delivered by the generator.
• Table 5 effect of heating the sample. It is therefore necessary to maintain the relative humidity, measured at the temperature of the object if it is different from the temperature of the humidification chamber, above a critical value estimated at around 50%. It is interesting to note that it is not necessary to humidify the objects or to cause uniform condensation: the object and the humidifier can remain at the same temperature. The inventors have further verified that sterilization is effective even on wet objects.
• the electric discharge produces a power which dissipates on the level of the gas of the zone of discharge and the electrodes.
• This heating can cause a rise in temperature of the surfaces to be sterilized and therefore suppress the sporicidal effect by reducing the local relative humidity as has been shown with table 3 above.
• certain discharge regimes are not electrically attainable without a certain minimum instantaneous electrical power. This is for example the case in DBD type discharge: there is necessarily a minimum power to be dissipated by the synchronous current before the appearance of the high amplitude pulses associated with this regime.
• a first solution consists in reducing heating by using a pulsed alternating supply or with a rectangular envelope making it possible to reduce the average dissipated power while retaining sufficient instantaneous electric power.
• a second solution consists, when the humidifier is an evaporative humidifier, of maintaining the temperature of the humidifier at a temperature close to and slightly below the temperature of the surface to be sterilized so as to maintain a constant relative humidity at the level of the 'object.
• This configuration only applies in the case of simple surfaces whose temperature can be measured directly or estimated from the temperature of the surrounding gas. In addition, it must be ensured that there is no cold spot between the humidifier and the discharge area.
• Another solution is to use a vaporizing humidifier to supersaturate the gas with water so that the relative humidity after heating is sufficient.
• the discharge also serves as an evaporator for the micro-droplets created by the humidifier: the vaporization is adjusted so as to maintain the humidity at the temperature of the object at a sufficient level.
• This configuration requires precise control of the temperature gradients and only works if the quantity of microdroplets required does not exceed the limit acceptable by the discharge.
• the first phase of bringing the reactor into equilibrium ends when the sterilizing action of the species produced by the second plasma can effectively begin, that is to say when the chemical conditions are favorable for sterilization, both in terms of humidity and of more general chemical equilibrium.
• the supply of water vapor is provided by the gas flow passing through the humidification chamber: it is therefore limited by the capacity of the humidification chamber to humidify a given flow.
• the effect of the discharge of the first plasma is limited by the maximum production of the discharge zone which is a function of the flow. In the general case, there is therefore an optimum flow rate which must take account of the two objectives. In some cases, the introduction of moisture and the discharge of the first plasma may not be simultaneous.
• the humidity measured at the sensor 46 makes it possible to verify that the necessary humidity threshold is reached.
• the discharge of the first plasma is chosen so as to minimize the time for bringing the enclosure into equilibrium.
• the power must be chosen so as to guarantee an acceptable temperature at the end of the treatment cycle. This can for example imply applying a decreasing power over time to allow a return to a lower temperature.
• the discharge of the second plasma is chosen according to its sporicidal action in the presence of moisture. Its power is limited to guarantee an acceptable temperature throughout its duration.
• the inventors have shown, for example (see Table 6 below) that the streamer regime in continuous voltage or the regime in pulsed DBD discharge had a sporicidal action leading to decimal reduction times D measured on bacterial spores of Bacillus subtilis of the order of a few minutes for powers less than 1W / L
• Table 6 comparison between the DC voltage discharge and the DBD discharge.
• the sensor 46 makes it possible to verify that the humidity is sufficient throughout the course of the Phb phase.
• the discharges of the Pha and Phb phases can be produced at the same time (different sources, superimposable electrical signals, etc.), it may be advantageous to ensure an overlap of the Pha and Phb phases , the Phb phase starting before the end of the Pha phase.
• the filling of the treatment enclosure with the gas of the Phb phase is completed at the end of the Pha phase and the Phb phase is then immediately operational.
• the third phase Phc is a rinsing phase carried out from the non-humidified gas.
• the main parameter is therefore the flow depending on the volume of the enclosure.
• the multi-parameter sensor 46 placed at the outlet of the treatment enclosure 10 makes it possible to determine the end of the Phc phase corresponding to the return to a chemical composition acceptable for storage.
• the criterion is based on the measurement of humidity and ozone provided by this sensor.
• the ozone sensor is preferably a sensor operating in an intermediate range, typically 1 to 3000 ppm
• FIG. 4 A first exemplary embodiment of a sterilization device in accordance with the principle stated above is illustrated in FIG. 4. It is a modular assembly with a central unit 60 to which are connected different types of treatment chambers 74- 80, 120.
• This modular configuration makes it possible to process, simultaneously or not, a set of speakers adapted in number, shape and volume to these objects from a single central unit comprising one or more high voltage power supplies and a single gas management system (ensuring supply and recovery) contained in the central unit.
• the use of several high voltage power supplies and several humidification chambers simplifies the regulation system and allows asynchronous use of different boxes and the use of several multi-parameter sensors makes it possible to control the composition of the gas recovered before filtration to determine or check the time associated with each phase.
• the sterilization zone can be of variable size or standardized according to the needs of the user.
• By adapting the shape and volume of the area to the objects to be sterilized it is possible to optimize the circulation of the sterilizing agent (its flow speed and its concentration) around the objects and thus to ensure a homogeneous treatment.
• the gas after treatment is then returned to this central unit by one or more gas discharge inlets.
• This type of device can be proposed because the low cost of implementing the method makes it possible to multiply the treatment zones and therefore to fragment the volumes treated.
• This modular assembly comprises a common central unit containing the source of gas mixture, one or more humidification chambers and one or more high voltage power supplies.
• the central unit 60 comprises one or more gas outlets (for example 62) and a corresponding number of high voltage outlets (for example 64) supplying one or more treatment chambers each comprising a plasma production area 68, 70, 72 corresponding to the plasma production zone 10a and supplying sterilizing gas to a sterilization zone 76, 78, 80 corresponding to the sterilization zone 10b containing the objects to be treated.
• the plasma production and sterilization zones can form two distinct zones of the same enclosure (for example enclosures 74 and 130), or they can each integrate a separate enclosure then called plasma production enclosure (in the case of enclosures 68, 70, 72) or sterilization enclosure (for enclosures 76, 78, 80).
• all or part of the entire device is placed in a Faraday cage to limit the interference created by the discharge.
• Indicating and control means 84, 86, 88, 90 arranged on the central unit 60 opposite the corresponding speakers with which they are associated make it possible to ensure individual control of each enclosure by ensuring the start of the sterilization cycle and the adjustment of the time of the different phases of the treatment, by adjusting the set flow rate, the appropriate regulation current and the signal form voltage, and possibly by defining the composition of the gas mixture to be used.
• the volume of the enclosure determines the number and size of the plasma sources used: it therefore has a direct influence on the flow and current setpoint. This setpoint also depends on the discharge regime chosen, and therefore on the phase in progress.
• the follow-up of the various commands is ensured by the output of a label printed 94 on a printer 96 integrated into the central unit 60.
• the loudspeakers can be fitted with an automatic identification system, for example based on bar codes or 98a electronic labels of the RFID (RadioFrequency IDdentification) type or of the IRC (InfraRed Communication) type, which allows via '' a corresponding reader 98b of the central unit to automatically determine the values of desired flow rate and the current of regulation and to calculate the time of the various phases of the cycle of sterilization.
• RFID RadioFrequency IDdentification
• IRC InfraRed Communication
• FIGS. 5 and 5a illustrate an exemplary embodiment of a treatment enclosure more specifically adapted to the sterilization of an endoscope and provided with a single plasma production zone.
• This treatment chamber 120 is characterized by a particular geometry of the electrodes constituting the plasma production zone which also allows the in situ production of sterilizing chemical species. Indeed, with conventional sterilization techniques, the internal areas of objects can pose sterilization difficulties if the active ingredients have difficulty reaching them. The problem is particularly true for cavities or the interior of tubes, as for example in the case of endoscope channels. However, the sterilization method of the invention which can perfectly be applied to the sterilization of these cavities also makes it possible to simply solve this problem of access to these internal zones of objects of very elongated shape.
• the enclosure 120 is in the form of a hermetically sealed casing, the interior space of which (the sterilization zone proper) is arranged according to the shape of the object to be treated 122.
• the endoscope being folded flat in the enclosure, it is defined a single plasma production area 124 at the level of the head 126 of the endoscope.
• the carrier gas is brought to the housing of the central unit 60 by an external link 128 and is redistributed to the plasma production zone respectively by an internal pipe 130.
• the electrodes of this plasma production zone are connected by a link 132 to an external high voltage connector 134 in connection with a corresponding compatible connector 136 of the common central unit 60.
• a link 138 allows the evacuation to this central unit 60 of the gas after treatment.
• the sterilization zone is formed of a first zone 142 surrounding the head of the endoscope 126 and maintained at slight overpressure to ensure the desired flow rate at the inside the channel 140, the rest of the instrument being placed in a second zone 144 separated from the previous one by a passage 146 of determined diameter and which will allow the treatment of the external surface of the endoscope.
• This passage by creating an annular restriction around the endoscope keeps the first zone 142 slightly under pressure.
• non-return valves and / or anti-bacterial filters are provided at the interfaces of the housing 100 to ensure its tightness after its disconnection from the common central unit 60. Individual control of this housing is ensured by means of indication and control 92 placed on the central unit.
• the improved process thus described is both simple in design, since the enclosure does not need to resist differences in high pressure and the gas supply system is simplified and easy to use, since there are no chemicals to handle before and after the sterilization cycle and the risks of pollution are limited.
• the high voltage and low frequency power system has a simple structure and can be adapted to different configurations.
• the proposed applications relate mainly to the medical field, but the process can be extended to many other industrial applications, for example in the food or pharmaceutical fields.

Landscapes

• Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• General Health & Medical Sciences (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• Plasma & Fusion (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Apparatus For Disinfection Or Sterilisation (AREA)
• Accommodation For Nursing Or Treatment Tables (AREA)
• Food Preservation Except Freezing, Refrigeration, And Drying (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=8854372

Family Applications (1)

Country Status (6)

Families Citing this family (37)

Family Cites Families (7)

• 2000
  • 2000-09-15 FR FR0011829A patent/FR2814079B1/fr not_active Expired - Fee Related
• 2001
  • 2001-09-13 WO PCT/FR2001/002842 patent/WO2002022180A2/fr not_active Application Discontinuation
  • 2001-09-13 EP EP01972154A patent/EP1317292A2/de not_active Withdrawn
  • 2001-09-13 US US10/380,088 patent/US20040037736A1/en not_active Abandoned
  • 2001-09-13 AU AU2001291945A patent/AU2001291945A1/en not_active Abandoned
  • 2001-09-13 JP JP2002526428A patent/JP2004508143A/ja active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events