Sterilization monitor

Abstract

A sterilizer device comprises a sterilization chamber (101). A steam generator (104) is configured to inject steam into the sterilizer chamber (101). A first measurement device (110) is configured to detect a non-condensing gas inside the sterilization chamber (101). A second measurement device (106) comprises a tube (107) inside the sterilization chamber. The second measurement device (106) detects a condensation on an inner surface (304) of a measurement chamber (108) that is fluidly connected to an inside of the tube (107) at a distance from the open end (124). A thermometer (306) detects a temperature in the sterilization chamber (101).

Description

[0001] Sterilization monitor

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a sterilizer device. The invention further relates to a method of sterilizing a load in a sterilizer device.

[0004] BACKGROUND OF THE INVENTION

[0005] In the 1950s detailed microbiological studies on aqueous liquids [PERK56] have shown that at elevated temperatures the organisms present in these liquids are killed effectively [PRE55], The mechanism for the killing of these organisms is coagulation of proteins [SYK67], Sterilization is achieved if the liquid is kept at a certain elevated temperature for a sufficient amount of time. The results for aqueous liquids can be used for surface steam sterilization if the steam heats up all surfaces to be sterilized to the required temperature and forms condensate on these surfaces. The conditions for surface steam sterilization have been specified by the Medical Research Council [MRC59], These conditions contain predetermined time-temperature relations when steam of sufficient quality is present, for example, 3 minutes at 134 °C.

[0006] When sterilizing medical (surgical) instruments, all surfaces that can be in contact with the environmental air have to be sterile. This also may involve the inside surfaces of instruments. Since the 1990s Minimal Invasive Surgery (MIS) is developing fast. Instruments for MIS often contain narrow channels. Also, the inside of these channels have to be exposed to sterilization conditions. Whether or not these regions are reached by steam of sufficient quality to produce a condensate at the aimed sterilization temperature, depends on the steam penetration. The steam penetration in such channels appears to depend crucially on the details of the sterilization process [VDO13-1.VDO15],

[0007] To test if all surfaces are exposed to steam sterilization conditions the standards prescribe that a steam penetration test is performed each day before starting production with a steam sterilizer [e.g., ISO 17665 clause 12.2.4], The current golden standard for steam penetration tests is based on a textile towel pack [B&D63], Over the years this test has been specified in more detail in the standards [EN285, ISO11140-4], Also, the test packs have been reduced in size. However, it is questionable whether a textile towel pack can be used to test steam penetration in channels of medical devices, because the fluid dynamics in these two types of systems is completely different. Therefore, otherProcess Challenge Devices (PCD) have been developed. Examples are channels with one end open and at the other end a chamber I receptacle to accommodate a chemical or biological indicator [EN867-5, EN 13060, ISO11140-6],

[0008] EP3999844 describes a device for detecting a non-condensing gas, comprising a tube having an open end and a closed end . The tube and the closed end are closed with respect to a fluid. The open end is open to allow the fluid to move into and out of the tube, wherein the tube is configured to allow a condensed portion of the fluid to be removed from the tube by gravitation. The device comprises a heat sink configured to extract heat from the tube at the closed end of the tube. The device comprises at least one thermometer configured to measure a temperature of a second portion of the tube between the heat source and the closed end of the tube or the fluid inside that second portion of the tube. The device further comprises a heat source configured to heat a first portion of the tube up to a specific temperature, wherein the heat source is located between the open end of the tube and the heat sink.

[0009] EP3308803B1 describes a sterilizer apparatus, configured to perform a sterilizing process to sterilize a load. The apparatus comprises a sterilizer chamber configured to inject steam into the sterilizer chamber, a measurement device comprising a measurement chamber having a fluid connection to the sterilizer chamber, a light source configured to emit light into the measurement chamber, and a light detector configured to detect the light in the measurement chamber and convert the detected light into a detection signal. The measurement chamber comprises an orifice for supply of a dry gas. The orifice and the fluid connection with the sterilizer chamber are on opposite sides of the measurement chamber. The sterilizer apparatus is configured to automatically blow the dry gas through the orifice into the measurement chamber before or after the sterilizing procedure.

[0010] SUMMARY OF THE INVENTION

[0011] It would be advantageous to provide an improved device to monitor a sterilizer. To better address this concern, according to an aspect of the present disclosure, a sterilizer device is provided with

[0012] a sterilization chamber;

[0013] a steam generator configured to inject steam into the sterilizer chamber;

[0014] a first measurement device configured to detect a non-condensing gas inside the sterilization chamber;a second measurement device forming a tubular process challenge device, wherein the second measurement device comprises a tube inside the sterilization chamber, wherein the tube has an open end, and wherein the second measurement device is configured to detect a condensation on an inner surface of a measurement chamber that is fluidly connected to an inside of the tube at a distance from the open end; and

[0015] a thermometer configured to detect a temperature in the sterilization chamber. This combination provides improved check of the sterilization. With the first measurement device, the second measurement device, and the thermometer, the sterilization process can be checked at any desired time, during the sterilization process. The result is enhanced certainty that sterilization is successful. Unlike prior art tests, like a textile pack, the combination of both tests of the first and second measurement device provides a greater security that the entire load in the sterilizer is adequately sterilized. Experiments have found that especially the combination of absence of non-condensing gases with condensation of the surfaces to be sterilized provides for efficient and reliable sterilization. The tube acts as a process challenge device that may largely correspond in physical behavior to tubes in the sterilization load, so that the condensation detection is representative for any instruments with open channels, such as tubes, in the sterilization load. A combined test based on these two measurements provides therefore much more reliable indication of the quality of a sterilization session. This combined test also is substantially more reliable than common tests based on e.g. a textile pack.

[0016] The thermometer may be configured to detect a temperature of the measurement chamber. This helps to further ensure the sterilization is adequate. Temperature is an important ingredient of the sterilization, and by directly detecting the temperature at the measurement chamber, the condensation detection result may be validated against the measured temperature.

[0017] The sterilizer device may further comprise a control unit configured to receive a first signal from the first measurement device; receive a second signal from the second measurement device; receive a third signal from the thermometer, wherein the third signal is indicative of the temperature; and generate an indication of the sterilization status based on the first signal, the second signal and the third signal. This indication is useful to control the operation of the sterilizer by e.g. stopping sterilization when sterilization quality is acceptable. The indication can also be shown e.g. on a display to show sterilization progress or current sterilization strength. The indication can also be output in form of an alarm signal in case the sterilization cannot be completed with the desired sterilization quality.The control unit may be configured to generate the indication based on a time duration during which the measurements of the first measurement device have satisfied certain first predetermined criteria and a time period during which the measurements of the second measurement device have satisfied certain second predetermined criteria. When the conditions have been satisfied for a sufficiently long time, it is sufficiently clear that the load has been sterilized.

[0018] The at least one first predetermined criterion may include a criterion that a fraction of non-condensing gas inside the sterilization chamber is below a certain threshold; and the at least one second predetermined criterion may include a criterion that condensation is detected on the inner surface of the measurement chamber. The combination of these criteria is necessary to ensure proper sterilization.

[0019] Moreover, the at least one first predetermined criterion and / or the at least one second predetermined criterion may include a criterion based on a temperature of the tubular process challenge device. Sufficiently high temperature is another criterion to assess the sterilization.

[0020] The control unit may determine the indication of the sterilization status based on a set of equations S = ^=1^ti / D(Ti') x ctand / )[ / 0. ,jN] < fmax, wherein

[0021]

[0022] denotes a fraction of non-condensing gas; ctdenotes a presence of condensation, for example 1 for condensation detected, 0 for no condensation detected, and optionally a fractional value for an intermediate detection; Tt denotes a temperature during a time interval At; of the sterilization process; S denotes an indication of the sterilization status; and D(Tt) denotes the decimal reduction time, wherein the index i runs over the parts of the sterilization process of which an indication of the sterilization status has to be obtained, and the index j runs over the parts of the sterilization process of which the fraction of a non-condensing gas should be smaller than fmax. Such an equation represents that the condensation and non-condensing gas fraction should satisfy the desired range for a suitably long time period. This time period depends on the decimal reduction time, which decreases at increasing temperature T.

[0023] In the context of a sterilization procedure, the D-value, D(Tt), or decimal reduction time, is the time duration, at a given condition (e.g. temperature) or set of conditions, to achieve a one-log reduction, that is, to kill 90% of relevant microorganisms. Thus, after an exposure time of D(Tt) at temperature

[0024]

[0025] only 10% of the organisms originally present in a microbial colony would remain.

[0026] The control unit may be configured to generate an indication that sterilization is complete when S > Sminand / )[ / 0. ,jN] < fmax. If the condensation has been there longenough while there have been not too many non-condensing gases, the sterilization may be considered complete.

[0027] The control unit may be further configured to repeatedly receive the first and second signals and repeatedly generate the indication of the sterilization status, while keeping track of an amount of time in which the at least one first predetermined criterion and the at least one second predetermined criterion were met during a sterilization process. Keeping track of the sterilization status repeatedly using repeated measurements allow to ensure that the conditions are not only met one moment, but during the entire relevant parts of the sterilization process.

[0028] The control unit may be further configured to control the sterilizer during the sterilization process based on the repeatedly generated indication of the sterilization status. Certain control parameters may be adjustable, for example temperature or power of the steam generator may be controlled to satisfy the constraints. Conversely, if the measurements indicate the conditions are overly fulfilled, the sterilizer can be controlled to switch to a lower energy mode as long as the conditions remained fulfilled, in order to save unnecessary energy consumption.

[0029] The control unit may be configured to control a power of the steam generator, a temperature of the steam generated by the steam generator, or a duration of at least a phase of the sterilization process, based on the repeatedly generated indication of the sterilization status. These aspects are suitable for being dynamically altered in view of the sterilization status.

[0030] According to another aspect of the present disclosure, a measurement device for condensation detection is provided that may be suitable as the second measurement device. This measurement device may comprise a measurement chamber having a fluid connection to the sterilizer chamber through the tubular process challenge device, wherein the measurement chamber comprises a specularly reflecting surface; and wherein the sterilizer further comprises: a first optic fiber connected on a first end to a light source and connected to the measurement chamber on the second end, wherein the light source is configured to emit light into the first end of the first optic fiber and the first optic fiber is configured to guide the emitted light into the measurement chamber; and a second optic fiber connected on a first end to a light detector and connected to the measurement chamber on the second end, wherein the light detector is configured to detect light received at the first end of the second optic fiber and the second optic fiber is configured to guide reflected light from the measurement chamber to the light detector; wherein the second end of the first optic fiber and the second end of the second optic fiber are fixed adjacent and parallel to each other facing the specularly reflectingsurface. This device is suitable to detect the condensation. Also, the parallel arranged ends provide cost effective implementation with accurate detection.

[0031] For example, the distance from the inner surface of the measurement chamber to the open end of the tubular process challenge device may be at least equal to 90% of a length of a longest tube or longest channel in a sterilization load in the sterilizer chamber. This way the condensation status in the measurement chamber is comparable to the condensation status throughout even the longest tube or channel in the sterilization load. Preferably, the open end may be at least equal to the length of a longest tube or longest channel in a sterilization load in the sterilizer chamber.

[0032] According to another aspect of the present disclosure, a measurement device for non-condensing gas detection is provided that may be suitable as the first measurement device. This measurement device may comprise: a tube having an open end and a closed end, wherein the tube and the closed end are closed with respect to a fluid, and the open end is open to allow the fluid to move into and out of the tube, wherein the tube is configured to allow a condensed portion of the fluid to be removed from the tube by gravitation; a heat sink configured to extract heat from the tube at the closed end of the tube; a heat source configured to heat a first portion of the tube up to a specific temperature, wherein the heat source is located between the open end of the tube and the heat sink; and at least one thermometer configured to measure a temperature of a second portion of the tube between the heat source and the closed end of the tube or the fluid inside that second portion of the tube. Such a tube-based device was found to be a highly reliable detector of non-condensing gases.

[0033] According to another aspect of the present disclosure, a method of sterilizing a load in a sterilizer device is provided. The method comprises injecting steam into a sterilizer chamber; detecting a non-condensing gas inside the sterilization chamber using a first measurement device; detecting a a condensation on an inner surface of a measurement chamber that is fluidly connected to an inside of a tube at a distance from an open end of the tube, wherein the tube is inside the sterilization chamber; detecting a temperature in the sterilization chamber by a thermometer; and generating, by a control unit, an indication of a sterilization status based on the detected non-condensing gas, the detected condensation, and the detected temperature.

[0034] According to another aspect of the present disclosure, a method of sterilizing a load in a sterilizer is provided. The method comprises:

[0035] injecting steam into a sterilizer chamber;

[0036] detecting a non-condensing gas inside the sterilization chamber using a first measurement device;detecting a condensation on a surface inside a tubular process challenge device inside the sterilization chamber using a second measurement device;

[0037] measuring a temperature at the closed end of the tubular process challenge device; and

[0038] generating, by a control unit, an indication of a sterilization status based on the detected non-condensing gas, the detected condensation, and the measured temperature.

[0039] The person skilled in the art will understand that the features described above may be combined in any way deemed useful. Moreover, modifications and variations described in respect of the system may likewise be applied to the method and to the computer program product, and modifications and variations described in respect of the method may likewise be applied to the system and to the computer program product.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the following, aspects of the invention will be elucidated by means of examples, with reference to the drawings. The drawings are diagrammatic and may not be drawn to scale. Throughout the drawings, similar items may be marked with the same reference numerals.

[0042] FIG. 1 shows a schematic representation of a sterilizer apparatus with a first example sterilization monitoring apparatus.

[0043] FIG. 2 shows a schematic representation of a sterilizer apparatus with a second example sterilization monitoring apparatus.

[0044] FIG. 3 shows a schematic representation of a first example condensation detector.

[0045] FIG. 4 shows a schematic representation of a second example condensation detector.

[0046] FIG. 5 shows a schematic representation of a first example non-condensing gas detector.

[0047] FIG. 6 shows a schematic representation of a second example non-condensing gas detector.

[0048] FIG. 7 shows an example of output signals of the second example noncondensing gas detector.

[0049] FIG. 8 shows an example of output signals of the first example condensation detector.

[0050] FIG. 9 shows an example of integrated data of a non-condensing gas detector, a condensation detector and a temperature measurement.DETAILED DESCRIPTION OF EMBODIMENTS

[0051] Certain exemplary embodiments will be described in greater detail, with reference to the accompanying drawings.

[0052] The matters disclosed in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. Accordingly, it is apparent that the exemplary embodiments can be carried out without those specifically defined matters. Also, well-known operations or structures are not described in detail, since they would obscure the description with unnecessary detail.

[0053] Certain embodiments disclosed herein make use of two complementary devices to test and monitor steam sterilization conditions in the sterilizer chamber and at the worst-case locations of the load in real-time. The technique incorporates a device to quantitatively determine the steam quality and an (e.g. optical) setup to determine the presence of surface condensation at the end of a long tube, which serves as a Process Challenge Device (PCD). The technique can also be used for control of the steam sterilization process.

[0054] Steam quality and steam penetration are fundamentally different properties. A good steam quality (very small amounts of NCGs) is a necessity to heat up all parts of the load sufficiently fast. This is caused by the fact that even a small amount of NCGs significantly reduces the heat transfer coefficient [MINK66, ROSE69], A good steam penetration is necessary for the steam to reach all relevant locations in the load, e.g., the inner region of porous loads or the inner side of open channels in medical instruments. It is often argued that a bad steam quality also leads to a decrease of the steam penetration. In extreme cases this might be correct, but it should be noted that according to the standards the steam quality is insufficient when the NCG fraction is larger than 3.5 ml NCGs in 100 ml condensate [EN285, ST79], In case of air, this corresponds to an NCG mass fraction of about 3.5x1 O'5in the sterilizer chamber. Such a fraction would lead to a temperature (dew point) depression of only 0.0007 °C at the end of a PCD, which is almost three orders of magnitude smaller than the temperature measurement error of 0.5 °C allowed by the standards.

[0055] The above results show that two criteria for the steam composition are specified for steam sterilization. One refers to the free space in the chamber (the space in the sterilization chamber outside of the load), where the NCG fraction should be smaller or equal to 3.5 ml NCGs in 100 ml condensate [EN285, ST79], The other refers to all surfaces, including the inner surfaces of the objects to be sterilized. On these surfaces a water film has to be present to be able to claim sterilization [SYK67],Both the steam quality and the capacity for steam penetration of a sterilizer vary over the day [VD016], and therefore monitoring both properties over the day would lead to improved assessment. However, for many years, quantitative measurements of the steam quality (the fraction of NCGs) for every load was not possible.

[0056] European patent no. 3625553 and European patent no. 3999844 describe several devices capable of detecting a non-condensing gas. Nevertheless, even in case of sufficient steam quality, variations in the sterilization process itself (e.g., duration and depth of the evacuation cycles) might prohibit steam sterilization conditions in narrow channels during some of these processes. This makes it advantageous that also the steam penetration is monitored, preferably in every load, preferably using a reproducible and absolute method.

[0057] Fundamentally, the time-temperature relations for steam sterilization [MRC59] are only sufficient if condensate with the specified temperature is present on all surfaces to be sterilized. Since no direct methods were available to determine if this situation occurs in instruments with narrow channels, a large variety of methods with unsatisfactory reliability has been developed during the last 60 years.

[0058] One class of methods aims to determine if sterilization has been achieved by using biological or chemical indicators. Biological indicators (Bls), however, have the disadvantage that their integrity can only be guaranteed if the storage and handling is performed according to the specifications given by the manufacturer. Apart from this, the incubation time of the indicator will inevitably take time. Consequently, clearance of the sterilized loads will be delayed until the results of the indicators are available. Chemical indicators (Cis) have the drawback that they are rather inaccurate [VDO12] and many Cis have to be judged by subjective color interpretation [LIS4115068], Additionally, the Cl can only be interpreted after the complete sterilization cycle has been performed and the Cl is taken out of the load. Often the Cl is intended to mimic a biological killing mechanism, but the correspondence of the chemical reactions with the complex biological killing mechanism is not obvious. A further drawback is that the equipment used for the development of Bls and Cis is controlled based on pressure and temperature only [ISO18472], The steam composition or the amount of NCGs in the chamber of the vessel is not monitored. As a consequence, it is not defined or known in which steam composition the Bls and Cis are developed.

[0059] According to the standards [EN 285] a steam penetration test has to be performed before starting production with a steam sterilizer. Currently, a Bowie and Dick towel pack [B&D63, ISO11140-4] is the golden standard for the steam penetration tests. This test is based on chemical indicators. This leads to subjective interpretation of theresults. Also, many alternative tests claiming to meet the standard for alternative tests [ISO11140-4] appear to not fulfill their claims [KIRK12], A second drawback is that the steam penetration in a textile towel pack (porous material) is quite different from that in typical modern medical instruments with narrow channels used in (minimal invasive) surgery.

[0060] In standards hollow Process Challenge Devices (PCDs) are specified [EN867-5, EN13060, ISO11140-6], In the literature these devices are discussed and proven to not fulfill their claims [ESEN11, ESEN12], basically because of three reasons. First, the volume of the receptacle for the Bl or Cl at the end of the tube enhances the steam penetration compared to a regular tube, which may lead to false passes [VDO15], Second, for most chemical indicators the color (change) has to be interpreted by subjective human vision [VDO12], In case of a Bl incubation time is necessary. Third, during production the PCDs are used constantly. In between successive sterilization cycles the devices are not conditioned. This implies that the initial conditions before use can vary, causing a less reproducible and less reliable final result.

[0061] A number of physical or electronic steam penetration tests are available in the market. It has been reported that 3 out of 4 commercially available steam penetration test do not fulfill the claimed standard [BEN11], Test devices are described in [DE202006006926U1], [EP1230936A1], One device is based on the time derivative of the temperature [VDO13-2], [WO201047139], This device should only be used as a steam penetration test as specified in the ISO 11140 part 4 [ISO11140-4], Because the ISO 11140-4 defines that such a penetration test is only to be performed once a day before starting the production [ISO17665], this device is designed to use it only once a day. Also, it is calibrated to mimic the results of a textile towel pack [ISO 11140-4] (which makes it unsuitable to judge steam penetration in hollow instruments). Finally, like all biological and chemical monitoring products mentioned hereinabove, its operation involves manual handling by operators of sterilizers. This costs time in a production environment and has the risk of human errors.

[0062] It is known that over the day the steam penetration may vary [VDO16,EN285], This makes it advantageous that in every load the steam penetration is monitored instead of monitoring steam penetration only once a day. Although the standards specify that monitoring of every load should be performed, a reliable and quantitative method based on physical measurements was not available during the last 60 years. This fundamental shortcoming is eliminated by the present disclosure, which combines two complementary physical measurements: (1) a quantitative measurement of the NCG fraction in the sterilizer chamber and (2) the assessment of the steam penetration bydetermining if during the sterilization phase a condensate with the aimed temperature is present at the position that is most difficult to reach for steam. The combined results of these measurements may also provide information on the reproducibility of the sterilization process, which may be useful for, e.g., preventive maintenance of the sterilizer and reduction of validation activities. These measurement devices may be included in a sterilizer together with the sterilization load, so that the measurement can be performed for every sterilization cycle as desired.

[0063] The following optional aspects may be provided.

[0064] Measurement of both the steam quality and presence of condensation may be performed on a representative worst-case location, by properly placing the measurement devices. For example, the non-condensing gas detector may be placed near the steam inlet or further away from the steam inlet, for example on the side of the sterilization chamber opposite the steam inlet. By measuring non-condensing gases both near the steam inlet and further away from the steam inlet, it can be assessed how well the steam mixes with the gases in the sterilization chamber.

[0065] Physical measurements may provide direct information on the steam quality, the presence of condensation, the temperature and time, yielding full information on sterilization conditions. The system may be implemented to provide real-time information, similar to measurements of temperature by a thermometer and measurements of pressure by a barometer. This makes the results easy to interpret for the end user.

[0066] Since the measurement devices may be permanently fixed in the sterilizer chamber, no handling of indicators by the operating staff of the sterilizer is needed. This may reduce risk of human errors.

[0067] The measurement data may be collected in digital form and used in quality control systems of the sterilizer, hospital, or institution. The digital information can be coupled to patient files or to the instrument track and trace systems, for auditing and maintenance.

[0068] The devices described herein are sustainable since they do not need to use any disposable material, which leads to less waste of Bl (biological indicator) and / or Cl (chemical indicator) material. Also cost reductions are numerous, such as less human work, less disposable materials, less conditioned storage of indicator materials, and reduction of validation activities. No separate sterilization processes for testing, with for example a Bowie and Dick test pack, are needed anymore, leading to considerable savings in water and energy.In certain implementations, all variables that are relevant for steam sterilization conditions are directly monitored. Steam quality in the sterilizer chamber can be monitored for every load. Steam penetration in channeled devices can be monitored for every load. Surface sterilization conditions can be monitored at the worst-case representative location. The method does not rely on subjective human interpretation. The method yields information in real-time. The method yields insight on the steam sterilization processes. The method can replace steam quality and steam penetration tests as specified in the standards for steam sterilization [EN285, EN13060, ISO11140-4], No human handling of indicator material or devices is involved.

[0069] The presence of NCGs in the steam can be measured directly, so it does not need to be inferred from indirect measurements. The presence of condensation of steam can be measured directly, so it has not to be inferred from indirect measurements. The condensation measurements can be performed at the closed end of the PCD itself, directly probing the conditions at the worst-case positions in the loads to be sterilized. The use of optical fiber technology in the condensation measurement device can make the system immune to electric or magnetic interference. Because of the integrated temperature measurement, the system can offer the possibility to monitor directly whether sterilization conditions are satisfied or not. The data of the measurements may be made available in real-time, so they can be used for process control or process optimization.

[0070] For example, a sterilizer monitor, as described herein, can use two complementary devices: a device to measure steam quality (the fraction of NCGs in the sterilizer chamber) and a device to measure the occurrence of condensation at the closed end of a tube mimicking the longest channel of a wrapped instrument present in the load to be sterilized (worst-case location).

[0071] FIG. 1 shows a schematic representation of a sterilizer apparatus 100 with a sterilization monitoring apparatus. In the illustrated example, the sterilization monitoring apparatus is integrated with the sterilizer apparatus 100 and covers control unit 120, non-condensing gas detector 110, and process challenge device 106 with condensation detector 108. The sterilizer apparatus comprises walls 112 forming an at least substantially closable sterilizer chamber 101. The sterilizer chamber 101 may have a loadable space 125, in which load 126 may be put. For example, at least one of the walls 112 may comprise a closable opening (not illustrated) for inserting and removing the load 126 into and out of the sterilizer chamber 101. This load 126 may comprise for example a pack of textile and / or one or more medical devices to be sterilized. Such medical devices may include heavy instruments and / or tubular process instrumentssuch as catheters. These heavy instruments may warm up very slowly if substantial fractions of NCGs are present within the sterilizer chamber. Moreover, tubular process instruments or other instruments containing open channels only sterilize well if the hot vapor reaches all the way through the lumens of these instruments.

[0072] The sterilizer chamber 101 may be fluidly connected to a pump 105. When the sterilizer chamber 101 is closed, the pump 105 may be optionally be configured to perform a pumping operation to remove any fluid from the sterilizer chamber 101 to create a vacuum inside the sterilizer chamber 101. The sterilizer may also comprise a steam generator 104 including a water supply and facilities to vaporize and heat the water. The steam may be conditioned, so that steam that is injected into the sterilizer chamber 101 may have predetermined properties including for example a predetermined temperature and / or a predetermined humidity. The steam generator 105 may comprise an electrical or other type of heat source to heat and vaporize the water. Alternatively, the steam may be supplied from an external source, such as a central steam generator of a hospital.

[0073] A typical sterilization process comprises three phases. The first phase is the conditioning phase, during which the air that is initially present in the sterilizer chamber is removed and the load is heated up to the sterilization temperature. This is generally achieved by successive cycles of evacuating the chamber by the pump 105 and injecting saturated steam from the steam generator 104. The second phase is the actual sterilization phase, during which the sterilizer chamber is filled with saturated steam and kept at the specified temperature (generally by controlling the pressure) for a specified time. During the third phase the sterilizer chamber is evacuated to dry the load and finally filled with air to atmospheric pressure to return to a safe state where it can be opened. Notwithstanding the above-disclosed typical sterilization process, alternative processes may be used to achieve the steam sterilization. The measurement devices disclosed herein may be used in conjunction with any suitable sterilization process.

[0074] The sterilizer may comprise a control unit configured to analyze the measurement results of the NCG detector and the condensation detector, and generate an indication of the sterilization status. For example, the control unit may verify repeatedly if the level of NCG is below a predetermined fraction (either volume fraction or weight fraction) inside the sterilizer chamber. Moreover, the control unit may verify repeatedly if a sufficient amount of condensation was detected by the condensation detector. Moreover, the control unit may verify whether the temperature measured by a thermometer in the sterilizer chamber is above a predetermined minimal temperature. This way, the control unit can keep track of an amount of time during which all threeconditions are met. If the three conditions were met for a predetermined amount of time, sterilization may be considered to be completed.

[0075] Alternatively, the control unit may be configured to calculate the indication of the sterilization status based on a set of equations:

[0076] Zk

[0077]

[0078] Mi / D(Tt) x Ci

[0079] and

[0080] fj L / o ■ ■ A / v] — fmax

[0081] wherein ctdenotes a presence of condensation. This condensation value ctcan be a binary value 1 for condensation present or 0 for no condensation. Alternatively, a probability value between 0 and 1 can indicate the probability that condensation is present. 7) denotes a temperature during a time interval At; of the sterilization process. D(Tf) denotes the decimal reduction time. S denotes an indication of the condensation status: the time intervals during which the condensation was detected, wherein the index i of the summation runs over the relevant time intervals of the sterilization process of which an indication of the sterilization status has to be obtained.

[0082] The symbol fj denotes a fraction of non-condensing gas (volume fraction or weight fraction, for example) during a time interval j. and the index j runs over the parts of the sterilization process of which the fraction of a non-condensing gas should not exceed the predetermined maximum fraction fmax. The inequality indicates that the fraction should be smaller than the maximum fraction during all of the relevant time intervals j in a set of N+1 time intervals

[0083]

[0084] {y0JiJ2< relevant for the sterilization, wherein N is a non-negative integer.

[0085] Thus, the control unit may be configured to generate an indication that sterilization is complete when S > Sminand fj < fmax, for all j in a predetermined set of N+1 time intervals {y0i 2<

[0086]

[0087] wherein N is a non-negative integer.

[0088] FIG. 1 and FIG. 2 illustrate two examples of how a measurement device according to the present disclosure may be arranged with respect to the sterilizer chamber 101. However, these arrangements are only disclosed by means of examples, without limiting the present disclosure thereto. The sterilizer chamber 101 could be replaced with any kind of container in which a sterilization process takes place. The application of the measurement device to any kind of container may be realized in a similar way. As illustrated, the sterilization chamber 101 includes a space 125 fora load, where a load 126 to be sterilized may be placed.In the first example, shown in FIG. 1, the first measurement device 110, for detecting non-condensing gases, is fitted to the upper wall 150 of the sterilizer chamber 101 so that the first measurement device 110 extends outside of the sterilizer chamber 101. The first measurement device 110 has a tube 117 surrounded by insulation material 116. The first measurement device 110 further comprises a heat sink 111 at the end of the tube 117 away from the sterilizer chamber 101. The lumen of the tube 117 of the first measurement device 110 has a fluid connection to the interior of the sterilizer chamber 101 through an orifice 114 in the upper wall 150. The tube 117 of the first measurement device 110 is thermally insulated from the environment by an insulating material 116. In this way, heat transport in the radial direction from the tube 117 of the device 110 to the environment of the sterilizer is greatly reduced. A part of the heat sink 111 may be in thermal contact with the environment, either directly or indirectly, to transport heat away from the tube 117 towards the environment. A heat source 122 is provided near the open end of the tube.

[0089] The second measurement device 106, for detecting condensation, is also fitted to the upper wall 150 of the sterilizer chamber 101. The second measurement device 106 extends from the wall 110, in particular the upper wall 150, of the sterilizer chamber 101 into the sterilizer chamber 101. However, this is not a limitation. The second measurement device 106 can be fitted anywhere inside the sterilizer chamber 101. The second measurement device 106 comprises a measurement chamber 108 with an optical measurement system, which will be described in greater detail elsewhere in the present disclosure. Optic fibers 102, 103 extend from the measurement chamber 108 through an orifice 109 in the wall 150 of the sterilizer chamber 101 to a light emitter L and a light detector D, respectively. The tube 107 ends on one end in the closed measurement chamber 108 and is open on the other end 124. Control unit 120 is connected to the electric components of the two measurement devices 110, 106. Thus, the first and second measurement device 106, 110 can be operated by the control unit 120 and measurement results are transmitted to the control unit 120 for processing and / or storage. Moreover, the control unit 120 can also be connected to the steam generator 104 and to the vacuum pump 105 to control their operation, based on the measurement results. The control unit 120 can also be connected to user interface elements (not illustrated), such as display, buttons and / or touch screen, among others for receiving control signals and reporting sterilization results.

[0090] FIG. 2 shows a second example of a sterilizer 200 with a measurement apparatus for monitoring sterilization quality. The sterilizer 200 has sterilizer chamber 201 with a placeholder 225 for a load 226 to be sterilized with the aid of steam generator204 and vacuum pump 205. In the second example, the first measurement device 210 and the second measurement device 206 are fitted to the side wall 251.

[0091] In the second example, the first measurement device 210 extends outside of the sterilizer chamber 201 from the vertical side wall 251 of the sterilizer chamber 201. The first measurement device 210 has a tube 217 surrounded by insulation material 216. The tube 217 is bent so that it tends upwards vertically. The first measurement device 210 further comprises a heat sink 211 at the end of the tube 217 away from the sterilizer chamber 201. The lumen of the tube 217 of the first measurement device 210 has a fluid connection to the interior of the sterilizer chamber 201 through an orifice 214 in the side wall 251. The tube 217 of the first measurement device 210 is thermally insulated from the environment by an insulating material 216. In this way, heat transport in the radial direction from the tube 217 of the device 210 to the environment of the sterilizer is greatly reduced. A part of the heat sink 211 may be in thermal contact with the environment, either directly or indirectly, to transport heat away from the tube 217 towards the environment. A heat source 222 is provided near the open end of the tube.

[0092] The second measurement device 206, for detecting condensation, is also fitted to the side wall 251 of the sterilizer chamber 201. The second measurement device 206 extends from the wall 212, in particular the side wall 251 , of the sterilizer chamber 201 into the sterilizer chamber 201. However, this is not a limitation. The second measurement device 206 can be fitted anywhere inside the sterilizer chamber 201. The second measurement device 206 comprises a measurement chamber 208 with an optical measurement system, which will be described in greater detail elsewhere in the present disclosure. Optic fibers 202, 203 extend through an orifice 209 in the wall 251 of the sterilizer chamber 201 to a light emitter L and a light detector D, respectively. The tube 207 ends on one end in the closed measurement chamber 208 and is open on the other end 224. Control unit 220 is connected to the electric components of the two measurement devices 210, 206. Thus, the first and second measurement device 206, 210 can be operated by the control unit 220 and measurement results are transmitted to the control unit 220 for processing and / or storage. Moreover, the control unit 220 can also be connected to the steam generator 204 and to the vacuum pump 205 to control their operation, based on the measurement results. The control unit 220 can also be connected to user interface elements (not illustrated), such as display, buttons and / or touch screen, among others for receiving control signals and reporting sterilization results.

[0093] In a practical implementation, typically one first measurement device and one second measurement device may be provided. It does not matter where they aremounted, be it side wall 251 or upper wall 150. For example, in an alternative embodiment, the first measurement device 110 on the upper wall 150 may be combined with the second measurement device 206 on the side wall 251. Alternatively, the first measurement device 210 on the side wall 251 may be combined with the second measurement device 106 on the upper wall 150. Also, multiple first devices or multiple second devices may be provided for improved measurement accuracy throughout the sterilization chamber 101, 201.

[0094] In any of the above-described arrangements, the sensors, including the thermometers, optical detectors, and any electric measurement tools may be read out by a data-acquisition system, for example implemented in the control unit 120, 220, which processes and analyzes the temperature measurements, for example the temperature profile in the axial direction of the tube, and / or the cooling power applied to keep the heat sink 111, 211 or the closed end of the tube 117, 217 at the chosen temperature. This analysis may, for example, yield the fraction of air that is present in the steam-air mixture in the sterilizer chamber 101, 102. The analysis may involve looking up the detected temperature(s) and / or cooling power in a look-up table and retrieving the fraction of air from the look-up table. Alternatively, an equation describing the data in the look-up table can be used. The look-up table may be generated by suitable experiments and / or may be computed from a physical model describing the sensor properties. Similarly, the control unit 120, 220 may send commands to the light generator L and receive signals from the light detector D indicative of any light detected in the measurement chamber 108, 208, as well as from the thermometer of the measurement chamber 108, 208.

[0095] The control unit 120, 220 may be configured to control the operation of the sterilizer chamber 101 , 201 including injection of steam by the steam generator 104, 204 and removal of fluid from the sterilizer chamber by the vacuum pump 105, 205. Also, the control unit 120, 220 may be configured to receive the measurement signals and / or measurement data generated by the first measurement device 110, 210 and / or the second measurement device 106, 206. The control unit 120, 220 may be configured to control the heat source 122, 222 and / or the heat sink 111, 211, based on the received temperature measurements and optionally the power consumption of these components. The control unit 120, 220 may be configured to control the power applied by the heat source 122, 222 and / or heat sink 111, 211 so that a temperature at the respective component is kept as close as possible to (or within a certain range around) a certain predetermined temperature. This is referred to herein as keeping a constant temperature.The control unit 120, 220 may be configured to generate an alarm signal if the fraction of NCGs is determined to be above a predetermined threshold, if no condensation is detected, or if the temperature is too low. The control unit 120, 220 may also be configured to adapt dynamically, for instance, the timing of the sterilization process based on the sterilization status determined from these measurement results.

[0096] The control unit 120, 220 may be configured to provide real-time information about the measured values and / or computed values, in particular the sterilization status calculated from the combined measurements. Also, the control unit 120, 220 may be configured to detect the steam quality (the fraction of NCGs) during every sterilizing process.

[0097] Also, the control unit 120, 220 may be configured to deliver at least some of the detected and / or computed results to an external system (not illustrated), such as a hospital ‘track and trace’ information system. In such a system, the digital information may be coupled to specific patient files. Also, the digital information can be coupled to a relevant instrument. This relevant instrument can be the sterilizer device. Alternatively, digital information can be coupled to the device that was sterilized. Also, the digital information can be coupled to a maintenance system associated with the sterilizer device. For example, if malfunctioning is detected, the system can send a signal to a maintenance service, so that service may be provided to repair the sterilizer device. Additionally, the information of the sterilization process used for medical devices can be coupled to patient files in order to improve patient safety.

[0098] The devices and methods disclosed herein allow monitoring variables that are relevant for determining steam sterilization conditions. They allow monitoring steam quality for every load of the sterilizer. The device can provide the measurement information in real-time. Also, it can be used to obtain more insight in the steam sterilization processes.

[0099] The system offers the possibility to monitor directly whether sterilization conditions are satisfied or not. The data of the measurements can be made available in real-time, so they can be used for process control or process optimization.

[0100] The second measurement device 106, 206, to measure the occurrence of condensation, may be based on a principle similar to the chilled mirror hygrometer (CMH). This principle is based on the change of the reflection of light by a surface when vapor is condensing on that surface. Generally, the condensation starts in the form of small droplets, which changes the originally specular reflection to a diffuse reflection. This effect reduces the intensity of the reflected light at a suitably located light detector. The present device uses fiber optic components to guide the light from the light sourceto the reflecting surface and to guide the reflected light to the detector. The device can be used to assess the condensation of water vapor at the closed end of a tube of which the other (open) side is connected to a steam reservoir, e.g., a sterilizer chamber.

[0101] If the cross section of the measuring section matches the inner cross sections of the tube, the fluid dynamics in the tube itself will not be significantly affected. In that case, the assembly mimics for instance the channeled instruments used for minimal invasive surgery. That is advantageous to perform a steam penetration test for that kind of instruments.

[0102] FIG. 3 shows an example of a second measurement device 300, to detect water vapor condensation. The device comprises a light source L, such as a light emitting diode (LED) or a laser. The device further comprises a light detector D, such as a photodiode or a camera. The device further comprises a measurement chamber 305. This measurement chamber is preferably shielded from external light radiation. Light source L is optically coupled to light guide 301 at proximal end 310 of light guide 301. Light detector D is optically coupled to light guide 302 at proximal end 312 of light guide 302. The light source L and the light detector D are optically coupled to the interior of the measurement chamber 305 via optical guides 301 and 302, for example optical fibers, respectively. The optical guides 301 and 302 have respective ends 311, 313 where the light is transmitted into or received from the measurement chamber. The measurement chamber 305 comprises a reflecting surface 304, such as a flat mirror. The measurement chamber 305 further comprises an optical element 303, such as a lens, arranged in between the ends of the light guides 301 , 302 and the reflecting surface 304.

[0103] The light emitted by the light source L enters the measurement chamber 305 at the end 311 of the light guide 301 and leaves the chamber 305 at the end 313 of the light guide 302. Via light guide 302 the light is guided to the detector D. The diverging light beam emitted by the light guide 301 is collimated to a parallel beam by the optical element 303. Next, the light beam is reflected by the flat mirror 304 and converted by the optical element 303 back into a converging beam, which is collected by the light guide 302.

[0104] The distal ends 311, 313 of the light guides 301, 302, are arranged in parallel and adjacent to each other, so that the light bundle emitted by the first light guide 301 coincides, as much as possible, with the field of view of the second light guide 302. This allows an invertible optical path from the first light guide 301 through optical element 303 via mirror 304 back through optical element 303 to the second light guide 302.FIG. 4 shows an alternative arrangement of a second measurement device 400, in which the light from light source L is coupled into the proximal end 410 of light guide 401 and emitted by the distal end 411 of the light guide 401. The light is reflected by a (preferably concave) mirror 409 and coupled into the distal end 413 of the other light guide 402 to be detected by detector D at the proximal end 412 of the light guide 402.

[0105] In either arrangement, a tube 307, 407 can be fitted to the measurement chamber 305, 405 to create a Process Challenge Device. The inner diameter of this tube 307, 407 can be chosen in the order of a few mm to reflect the channels present in many medical instruments, but this diameter is not very critical. The NCG-water vapor mixture in the sterilizer chamber can enter the tube 307, 407 at its open end 308, 408 and reach the measurement chamber 305, 405 at the opposite end of the tube 307, 407 via flow and / or diffusion through the tube 307, 407.

[0106] Moreover, the temperature of the measurement chamber 305, 405 may be measured by a suitable thermometer 306, 406, for instance, a calibrated PtIOOO resistance thermometer. This allows to check the temperature in addition to the condensation status. This way, it is possible to prevent premature condensation of the NCG-water vapor mixture at a relatively cold region at the end of the Process Challenge Device to lead to unreliable sensor readings. The location, design and dimensions of the process challenge device of the second measurement device are such that during the relevant phases of the sterilization process the measuring chamber itself is fully warmed up from the outside by the NCG-water vapor mixture in the sterilizer chamber. The same should be true for the actual sterilization load.

[0107] To withstand the high temperatures and the eroding effects of the steam, the optical guides 301 , 302, 401 , 402 may be optical fibers of a fused silica / hard polymer or glass / glass type with a protective coating withstanding at least 150 °C. Multimode fibers with a core diameter in the range of, for example, 200 - 800 pm are suitable for this purpose. Also the optical element 303 should preferably be made of a material that can withstand the eroding effects of steam at elevated temperatures. The metal parts of the measurement chamber may be made of stainless steel (316L) or another material that is not eroded by saturated steam. Other materials and dimensions may be alternatively implemented.

[0108] For the first measurement device 110, 210, any suitable NCG detector may be used, for example, an NCG detector known from EP 3999844. In certain embodiments, the NCG detector may comprise a measurement device for detecting a gas, comprising a tube having an open end and a closed end, wherein the tube and the closed end are closed with respect to a fluid, and the open end is open to allow the fluid to move intoand out of the tube, wherein the tube is configured to allow a condensed portion of the fluid to be removed from the tube by gravitation; a heat sink configured to extract heat from the tube at the closed end of the tube; a heat source configured to heat a first portion of the tube up to a specific temperature, wherein the heat source is located between the open end of the tube and the heat sink; and at least one thermometer configured to measure a temperature of a second portion of the tube between the heat source and the closed end of the tube or the fluid inside that second portion of the tube.

[0109] The temperature of the wall of the tube is well-conditioned because the first portion of the tube is heated by the heat source. This way, the temperature of the tube is less influenced by factors external to the tube, such as an object to which the tube may be connected, or the temperature of the environment. The temperature profile of the tube in between the heat source and the heat sink may be largely determined by the composition of the gas mixture at the open end of the tube. This way, the information obtained from the tube, such as a measured temperature, provides more accurate information about the presence of a non-condensing gas inside the tube.

[0110] The heat source may be configured to keep the first portion of the tube at a constant temperature. This allows to set the temperature of the open end of the tube to a specific value, which is helpful to further avoid significant deviations of the temperature as a consequence of external factors. By keeping the temperature of the open end of the tube constant, the climate (condensation, temperature profile, etc.) inside the tube is largely determined by the content of the gas mixture that enters the tube through the open end of the tube.

[0111] The NCG detector may comprise a control unit configured to control the heat source based on a temperature obtained from a thermometer configured to measure a temperature of the first portion of the tube. This allows to control the temperature of the first portion accurately.

[0112] The control unit of the NCG detector may also be configured to control the heat sink based on a set-point for a temperature of the closed end of the tube. This allows to set the temperature of the closed end of the tube to a specific value, which is helpful to avoid significant deviations of the temperature caused by e.g. the content of the gas mixture flowing into the tube. By keeping the temperature of the closed end of the tube constant, condensation of the condensing gases, such as water, may be controlled better than by an unregulated heat sink.

[0113] The control unit of the NCG detector may be configured to control the heat sink based on a temperature obtained from the at least one thermometer in respect of theclosed end of the tube. This way the heat sink may be controlled to realize e.g. a constant temperature or a well-defined temperature at the closed end.

[0114] The tube of the NCG detector may be enclosed by a thermally insulating layer. This makes the temperature profile measurements less sensitive to variations of environmental temperature.

[0115] The measurement device of the NCG detector may comprise a control unit configured to determine information about a composition of the fluid inside the tube, in particular about a presence of any non-condensing gas in the fluid, based on a temperature obtained from the at least one thermometer or a cooling power of the heat sink. Such a control unit may determine the composition efficiently. This control unit may be integrated with the control unit 120, 220.

[0116] The open end of the tube of the NCG detector may be fluidly connected to an inside of the sterilizer chamber via an opening in a wall of the sterilizer chamber, and wherein the sterilizer chamber is closable to form a substantially closable chamber that is fluidly connected to a lumen of the tube. This way the device can be suitably used to detect a non-condensing gas inside the sterilizer chamber.

[0117] The heat source of the NCG detector may be configured to heat the open end of the tube to a temperature above a temperature of the inside of the sterilizer chamber. This way, the measurement becomes more independent of the temperature of the inside of the sterilizer chamber. Inadvertent condensation due to too cold inflow of gas may be avoided.

[0118] The sterilizer chamber may have the opening in a side wall or an upper wall of the sterilizer chamber, wherein the chamber is fluidly connected to the inside of the tube via the opening. This allows to easily let the condensed fluid flow back into the chamber.

[0119] The tube may be fixed to the side wall or upper wall of the sterilizer chamber and the tube may protrude from the sterilizer chamber in an upward direction. This allows to easily let the condensed fluid flow back into the chamber. Moreover, non-condensed fluids may remain in the tube, thus influencing the temperature profile inside the tube.

[0120] The heat source of the NCG detector may be positioned outside the sterilizer chamber. This way any influence of the heat source on the sterilization process is avoided or reduced. Moreover, the temperature at the open end created by the heat source is less influenced by the temperature of the wall of the sterilizer chamber. This way, the heat source may be used, for example, without active temperature control. For example, the distance from the heat source to a wall of the sterilizer chamber, measured along the tube, may be at least 2 centimeters, preferably at least 4 centimeters.A distance between the heat sink and the heat source may be, for example, at least 5 centimeters, preferably at least 10 centimeters. This allows sufficient space for forming of a temperature profile inside the tube related to a presence of non-condensing gases.

[0121] A distance between the heat source and the open end of the tube or between the heat source and the wall of the sterilizer chamber, measured along the tube, may be, for example, at least 2 centimeters, preferably at least 4 centimeters. A distance may help to make it easier to control the temperature of the portion of the tube at the heat source.

[0122] In operation, the non-condensing gas may be detected by the NCG detector using the following procedure. First, providing a gas mixture to a tube having an open end and a closed end, wherein the tube and the closed end are closed with respect to the gas mixture, and the open end is open to allow the gas mixture to move into and out of the tube, wherein a condensed portion of the fluid is allowed to be removed from the tube by gravitation; and extracting heat from the tube at the closed end of the tube using a heat sink; heating a first portion of the tube up to a specific temperature using a heat source that is at a distance from the heat sink towards the open end of the tube; and measuring a temperature of a second portion of the tube between the heat source and the closed end of the tube or the fluid inside that second portion of the tube, using at least one thermometer.

[0123] FIG. 5 shows a device for detecting a non-condensing gas, as described above, that may be implemented in various ways, of which several examples are illustrated in FIG. 1 and FIG. 2. FIG. 5A shows a sectional side view and FIG. 5B shows a cross-sectional view. The illustrative device comprises a vertically oriented tube 501 with an open bottom end 505, which can be fluidly connected to the sterilizer chamber or another kind of space, whereas the other end 512 is closed. A heat source 521 is arranged near the open end 505 of the tube 501. A heat sink 506 is arranged near the closed end 512 of the tube 501, for example at the top 508 of the tube 501. The heat source 521 is configured to heat the open end of the tube to a temperature above the condensation temperature of the condensing gas, whereas the heat sink 506 is configured to cool the closed end of the tube to a temperature below the condensation temperature of the condensing gas.

[0124] The heat source 521 may comprise an electric heater, for example. Alternatively, the heat source 521 may be implemented by flushing a hot fluid along the wall of the tube, for example steam tapped from the steam generator of the sterilizer. Other implementations of the heat source may be apparent to the person skilled in the art onthe basis of the present disclosure. The heat source 521 may be controlled by a control unit to realize a predetermined temperature at the open end 505 of the tube 501.

[0125] When in use, a mixture of steam and air 502 may enter the lumen 519 of the tube 501. As long as the wall of at least a portion of the tube has a lower temperature than the saturation temperature of the condensing gas in the gas mixture entering the tube, the steam will condense on the wall of the tube. The condensate 504 runs off the wall towards the bottom of the tube, where it leaves the tube through the open end 505. If the wall of at least a portion of the tube is kept at a temperature below the saturation temperature of the steam, this condensation will establish a continuous flow of steam (and possible non-condensing gas) into the tube during the process until the end of the sterilization phase. Non-condensing gas flowing with the steam into the tube will not condense and can only leave the tube 501 via the open end 505 of the tube by diffusion. However, diffusion is a very slow process compared to the flow initiated by the condensing steam on the wall. Therefore, in the tube, the non-condensing gas will accumulate and the concentration of the condensing gas will substantially decrease. This effect will be more pronounced towards the closed end 512 of the tube, where so much non-condensing gas 503 can be present that the condensing gas may not be able to penetrate all the way up to the closed end 512.

[0126] The heat transfer from the gas mixture to the wall 515 of the tube is dominated by the latent heat that is released during condensation of the steam. The presence of even small amounts of non-condensing gas will significantly reduce this heat transfer. Therefore, it is expected that the heat load on the tube close to the closed end 512 is smaller than the heat load on the tube close to the open end 505. This difference in heat load will be more pronounced when the fraction of non-condensing gas of the gas inflow is larger. More particularly, when more non-condensing gas has accumulated near the closed end of the tube, a larger portion of the tube near the closed end of the tube will be exposed to reduced heat load and thus will attain a lower temperature, and thus the temperature profile along the tube depends on the fraction of non-condensing gas in the gas mixture that flows into the tube, as the condensed gas (i.e. liquid) exits the tube.

[0127] FIG. 6 illustrates a perspective side view of an example of a measurement probe for detecting NCG in a fluid using the power needed to cool the closed end of the tube, which can be mounted to e.g. the upper wall of a sterilizer chamber. By bending the tube, such a device can alternatively be made for mounting to the side wall of the sterilizer, as shown in FIG. 2. A thermal resistance 611 has been included between the heat sink 606 and the closed end 612 of the tube 601. A thermometer 607 may be attached to the heat sink 606, to monitor and / or control the temperature of the heat sink606. Two thermometers 610 may be attached to the thermal resistance 611 between the heat sink 606 and the closed end 612 of the tube 601. Of the two thermometers 610, a first thermometer 610a is fixed closer to the heat sink 606 than a second thermometer 610b, and the second thermometer 610b is fixed closer to the closed end 612 of the tube 601 than the first thermometer 610a. Advantageously, the second thermometer 610b is used as a feedback temperature to control the heat sink 606. That way the closed end of the tube may be controlled relatively accurately.

[0128] At least two different ways are possible to determine the power consumed to cool the closed end 612 of the tube 601 to a chosen temperature. First, the power can be deduced from the externally supplied cooling power (either thermal or electric), while keeping the temperature measured with the thermometer 610b at the chosen temperature. Second, this cooling power can alternatively be deduced from the temperature difference between the two thermometers 610a, 610b attached to the thermal resistance 611. In the latter case variations of the observed cooling power due to changes in the environmental temperature may be strongly suppressed, which may improve the accuracy of the measurement of the NCG fraction. It should be noted that if the cooling power is deduced from the externally supplied cooling power, only one of the thermometers illustrated at 607 and 610a, 610b are needed, and the remaining illustrated thermometers can be omitted. It should be noted that the realization depicted in FIG. 6 is only an example. Other configurations of NCG detectors are possible, as e.g. disclosed in EP 3999844.

[0129] In an alternative implementation, the tube 501 of the first measurement device may be fixed or positioned loosely inside the sterilizer chamber containing the fluid to be analyzed. Insulation material around the tube may be provided to still be able to create the temperature conditions as described hereinabove. If the heat sink 506 is a passive heat sink, such as a thermal capacitor, which may be made from aluminum, the insulating material may be provided around the heat sink as well. If the heat sink 506 comprises an active cooling element, for example a Peltier element, the insulation material may be omitted at a hot side of the cooling element, so that heat can be actively removed from the tube 501. The hot side of the cooling element may be attached to an opening in the wall of the container, so that the cooling element can operate more efficiently.

[0130] By appropriately tuning the temperatures, including the target temperature of the heat sink and the look-up tables correlating measurements with information regarding NCGs, the first measurement device can be used to detect non-condensing fluids in other gases.In use, a sterilization process may be conducted and monitored using a sterilizer, by injecting steam into a sterilizer chamber; detecting a non-condensing gas inside the sterilization chamber using a first measurement device; detecting a condensation on a surface inside a tubular process challenge device inside the sterilization chamber using a second measurement device; detecting a temperature in the sterilization chamber, for example at the closed end of the tubular process challenge device, by a thermometer; and generating, by a control unit, an indication of a sterilization status based on the detected non-condensing gas and the detected condensation. For example, the control unit may control the steam generator that injects the steam into the sterilizer chamber based on the measurement results.

[0131] FIGs. 7, 8, and 9 show an example of measurements made during a sterilization procedure with a sterilizer device as set forth herein.

[0132] FIG. 7 shows a set of data for a typical sterilization process generated by a first measurement device illustrated in FIG. 6 and a temperature measured by for instance a thermometer attached to the measuring chamber of the second measuring device (306, 406 in Figs. 3,4), The curves labelled Pt1 to Pt5 show the temperatures in degrees Celsius measured by the first measurement device. Pt1 is the temperature of the fan on hot side of the Peltier cooling element. It is used to trigger an alarm when overheating occurs. Pt2 (607 in FIG.6) is the temperature of the heat sink. Pt3 (610a) and Pt4 (610b) are the temperatures used to calculate the heat flow through the heat resistance 611. Pt5 (622) is the temperature of the heat source 621. Pt6 shows the temperature measured by for instance a thermometer attached to the measuring chamber of the second measuring device. The curve labelled “pres” shows the pressure in the sterilizer chamber in kPa. This pressure is measured to identify the parts of the sterilization process of which an indication of the sterilization status has to be obtained.

[0133] FIG. 8 shows a set of data for a typical sterilization process generated by a second measurement device as illustrated in FIG. 3. The curve labelled “Inorm” shows the intensity (in an arbitrary normalized unit) of the reflected light measured by the detector D in FIG. 3 divided by a reference intensity measured by the same detector in the absence of condensation, for instance, when the sterilizer chamber is filled with only air. The curve labelled “pres” shows the pressure in kPa, which is measured to identify the parts of the sterilization process during which condensation should occur. The gray horizontal bar 801 denotes a threshold which can be set in the controller of the measuring devices. Only when the normalized light intensity “Inorm” drops below this threshold, the controller will signal that condensation occurs.FIG. 9 shows an integration of data generated by the first and second measurement device for a typical sterilization process. The curve labelled “pres” shows the measurements of the pressure in the sterilizer chamber. This curve is shown to visualize the different phases of the sterilization process. The curve labelled “temp” shows the temperature in degrees Celsius measured by for instance a thermometer attached to the measuring chamber of the second measurement device. The plateau 901 at the highest pressure (and temperature) corresponds to the sterilization phase. In this example the temperature is within the temperature region allowed by the standards (indicated in FIG.9 by horizontal dashed-dotted lines at 134 and 137 degrees Celsius) during the sterilization phase. The curve labelled “dTsink” shows the temperature difference between for instance the thermometers 610a and 610b of the second measurement device shown in FIG. 6, from which the heat flow through the heat resistance (611 in FIG.6) can be derived. The scale of this temperature difference is multiplied by 6 for clarity. Using for instance a look-up table or a mathematical relation fitted to the data in that look-up table the value of the temperature difference dTsink can be converted to an amount of NCGs and vice versa. The horizontal gray bar 902 shows the maximum amount of NCGs converted to a minimum value of dTsink, including all possible uncertainties. If the value of dTsink is above this tolerance band 902 during the sterilization phase, the amount of NCGs is definitely below the allowed maximum. If the value of dTsink is below this tolerance band 902 during the sterilization phase, the amount of NCGs is definitely above this maximum. If the value of dTsink is within the tolerance band 902, the amount of NCGs may be acceptable, depending on the safety margins which are applied. In this example the amount of NCGs is definitely below the allowed maximum. The vertical gray bar 903 shows the time interval during which condensation is detected by the first measurement device. In this example condensation occurs during the entire sterilization phase.

[0134] An example of a sterilizer device has a sterilization chamber; a steam generator configured to inject steam into the sterilizer chamber; a first measurement device configured to detect a non-condensing gas inside the sterilization chamber; a tubular process challenge device inside the sterilization chamber; a second measurement device configured to detect a condensation on a surface inside the tubular process challenge device; and a thermometer configured to detect a temperature in the sterilization chamber.

[0135] Some or all aspects of the invention may be suitable for being implemented in form of software, in particular a computer program product. The computer program product may comprise a computer program stored on a non-transitory computer-readable media. Also, the computer program may be represented by a signal, such as an optic signal or an electro-magnetic signal, carried by a transmission medium such as an optic fiber cable or the air. The computer program may partly or entirely have the form of source code, object code, or pseudo code, suitable for being executed by a computer system. For example, the code may be executable by one or more processors.

[0136] The examples and embodiments described herein serve to illustrate rather than limit the invention. The person skilled in the art will be able to design alternative embodiments without departing from the spirit and scope of the present disclosure, as defined by the appended claims and their equivalents. Reference signs placed in parentheses in the claims shall not be interpreted to limit the scope of the claims. Items described as separate entities in the claims or the description may be implemented as a single hardware or software item combining the features of the items described.

[0137] Non Patent Citations

[0138] [BEN11] Benoit F, Merger D, Hermsen RJ, and van Doornmalen JPCM. A comparison of four commercially available electronic steam penetration tests according to ISO 11140 part 4. Central Service, 3:180-184, 2011.

[0139] [B&D63] Bowie JH, Kelsey JC, and Thompson GR. The Bowie and Dick autoclave tape test. The Lancet, 281:568-569, 1963.

[0140] [ESEN11] Esen S and van Doornmalen JPCM. One set of requirements for steam penetration tests is enough. Central Service, 5:365-367, 2011.

[0141] [ESEN12] Esen S, Tessarolo F, Hermsen RJ, and van Doornmalen JPCM.

[0142] Current reference devices for hollow instrument loads as defined in standards are not a valid steam penetration test. Central Service, 4:256-260, 2012.

[0143] [EN 285] European Committee for Standardization. Standard EN 285:2015+A1:2021. sterilization - steam sterilizers - large sterilizers, 2021.

[0144] [EN 13060] European Committee for Standardization. Standard EN 13060:2014+A1:2018. Small Steam Sterilizers. European standard, 2O18.[IAWPS]Wagner W, Cooper JR, Dittmann A, Kijima J, Kretzschmar HJ, Kruse A, Mares R, Oguchi K, Sato H, Stocker I, Sifner O, Takaishi Y, Tanishita I, and Trubenbach IJ. The IAWPS industrial formulation 1997 for the thermodynamic properties of water and steam. Transactions of the ASME, 122:150-182, 2000.[ISO11140-4] International Organization for Standardization. Standard ISO 11140-4 Sterilization of health care products - Chemical indicators - Part 4: Class 2 indicators as an alternative to the Bowie and Dick-type test for detection of steam penetration. ISO standard, 2007.

[0145] [ISO11140-6] International Organization for Standardization. Standard ISO 11140- 4:2022, Sterilization of health care products - Chemical indicators - Part 6: Type 2 indicators and process challenge devices for use in performance testing of small steam sterilizers, 2022

[0146] [I S017665] International Organisation for Standardisation. Standard ISO 17665-1.

[0147] Sterilization of health care products -Moist heat, international organization for standardization, 2024.

[0148] [I S018472], International Organization for Standardization. Standard Sterilization of health care products - Biological and chemical indicators - Test equipment, 2018.

[0149] [KIRK12] Kirk B. An evaluation of nine Bowie and Dick test products available in the United Kingdom. Medical Device Decontamination 2012; 17(1): 8- 23.

[0150] [MRC59] Working party on Pressure Steam Sterilizers of the Medical Research Council. Sterilisation by steam under increased pressure. The Lancet, 273:425-435, 1959.

[0151] [MINK66] Minkowycz Wand Sparrow E. Condensation heat transfer in the presence of noncondensables, interfacial resistance, superheating, variable properties, and diffusion. Int. J. Heat Mass Transfer 9:1125- 11441966.

[0152] [PERK56] Perkins JJ. Principles and Methods of Sterilization. Charles C Thomas,

[0153] Springfeld (IL), 1956.

[0154] [PRE55] Precht JCH. Temperatur und Leben. Springer Verlag, Berlin, 1955. [ROSE69] Rose JW. Condensation of a vapour in the presence of a noncondensing gas, Int. J. heat mass transfer 12:233-2371969.

[0155] [ST79] ANSI / AAMI ST79:2017 / (R)2022. Comprehensive guide to steam sterilization an sterility assurance in health care facilities, 2022.

[0156] [SYK67] Sykes G. Disinfection & sterilization. 2nd edition with corrections. E & FN Spon Ltd, London, 1967.

[0157] [VDO12] van Doornmalen JPCM, Hermsen RJ, and Kopinga K. Six commercially available class 6 chemical indicators tested against their stated values. Central Service, 6:400-404, 2012.[VD013-1] van Doornmalen JPCM, Verschueren M, and Kopinga K. Penetration of water vapour into narrow channels during steam sterilization processes. Journal of Physics D: Applied Physics, 46:065201, 2013.

[0158] [VDO13-2] van Doornmalen JPCM and Kopinga K. Measuring non-condensable gases in steam. Review of Scientific Instruments, 84:115106, 2013. [VDO15] van Doornmalen JPCM and Kopinga K. Steam penetration in thinwalled channels and helix shaped process challenge devices. Central Service, 6:429-433, 2015.

[0159] [VDO16] van Doornmalen JPCM and Riethoff W. A case study of steam penetration monitoring indicates the necessity of Every Load Monitoring of steam sterilization processes. Central Service. 24: 315-324, 2016.

Claims

CLAIMS:

1. A sterilizer device comprising:a sterilization chamber (101);a steam generator (104) configured to inject steam into the sterilizer chamber (101);a first measurement device (110) configured to detect a non-condensing gas inside the sterilization chamber (101);a second measurement device (106) forming a tubular process challenge device, wherein the second measurement device comprises a tube (107) inside the sterilization chamber, wherein the tube (107) has an open end (124), and wherein the second measurement device (106) is configured to detect a condensation on an inner surface (304) of a measurement chamber (108) that is fluidly connected to an inside of the tube (107) at a distance from the open end (124); anda thermometer (306) configured to detect a temperature in the sterilization chamber (101).

2. The sterilizer device according to claim 1, wherein the thermometer (306) is configured to detect the temperature of the measurement chamber (108).

3. The sterilizer device according to claim 1 or 2, further comprising a control unit (120) configured to:receive a first signal from the first measurement device (110);receive a second signal from the second measurement device (106); receive a third signal from the thermometer (306), wherein the third signal is indicative of the temperature; andgenerate an indication of the sterilization status based on the first signal, the second signal, and the third signal.

4. The sterilizer device according to claim 3, wherein the control unit (120) is configured to generate the indication based on a time period during which the measurements of the first measurement device (110) have satisfied at least one first predetermined criterion and a time period during which the measurements of the second measurement device (106) have satisfied at least one second predetermined criterion.

5. The sterilizer device according to claim 4, whereinthe at least one first predetermined criterion includes a criterion that a fraction of non-condensing gas inside the sterilization chamber (101) is below a certain threshold; andthe at least one second predetermined criterion includes a criterion that condensation is detected on the inner surface (304) of the measurement chamber (108).

6. The sterilizer device according to claim 5, wherein the at least one first predetermined criterion and / or the at least one second predetermined criterion includes a criterion based on a temperature of the measurement chamber (108).

7. The sterilizer device according to any one of claims 4 to 6, wherein the control unit (120) is configured to calculate the indication of the sterilization status based on a set of equations:ZkMi / D(Tt) x Ciandfj fmax, for all j in a set {j0,whereinfj denotes a fraction of non-condensing gas;ci denotes a presence of condensation;Ti denotes a temperature during a time interval At; of the sterilization process; S denotes an indication of the condensation status;D(Tf) denotes a decimal reduction time at temperature Ifk is a positive integer, andN is a non-negative integer,wherein the index i runs over the parts of the sterilization process of which an indication of the sterilization status has to be obtained, and the index j runs over the parts of the sterilization process of which the fraction of a non-condensing gas should be smaller than fmax.

8. The sterilizer device according to claim 7, wherein the control unit (120) is configured to generate an indication that sterilization is complete when S > Sminand fj fmax, for all j in the set {j0,j1jN}.

9. The sterilizer device according to any one of claims 3 to 8, wherein the control unit (120) is further configured to repeatedly receive the first, second, and third signals, corresponding to successive measurements, and repeatedly generate the indication of the sterilization status, while keeping track of an amount of time in which the at least one first predetermined criterion and the at least one second predetermined criterion were met during a sterilization process.

10. The sterilizer device according to claim 9, wherein the control unit (120) is further configured to control the sterilizer device (100) during the sterilization process based on the repeatedly generated indication of the sterilization status.

11. The sterilizer device according to any one of the preceding claims, wherein the control unit (120) is configured to control a power of the steam generator (104), a temperature of the steam generated by the steam generator (104), or a duration of at least a phase of the sterilization process, based on the generated indication of the sterilization status.

12. The sterilizer device according to any one of the preceding claims, wherein the measurement chamber (305, 405) of the second measurement device (300, 400) has a fluid connection to the sterilizer chamber (101) through the tube (307, 407),wherein the measurement chamber (305, 405) comprises a specularly reflecting surface (304, 409); andwherein the sterilizer device further comprises:a first optic fiber (301, 401) connected on a first end (310, 410) to a light source (L) and connected to the measurement chamber (305, 405) on the second end (311, 411), wherein the light source (L) is configured to emit light into the first end (310, 410) of the first optic fiber (301, 401) and the first optic fiber (301, 401) is configured to guide the emitted light into the measurement chamber (305, 405); anda second optic fiber (302, 402) connected on a first end (312, 412) to a light detector (D) and connected to the measurement chamber (305, 405) on the second end (311 , 411), wherein the light detector (D) is configured to detect light received from the second optic fiber (302, 402) at the first end (312, 412) of the second optic fiber (302, 402) and the second optic fiber (302, 402) is configured to guide reflected light from the measurement chamber (305, 405) to the light detector (D);wherein the second end (311, 411) of the first optic fiber (301, 401) and the second end (311, 411) of the second optic fiber (302, 402) are fixed adjacent and parallel to each other facing the specularly reflecting surface (304, 409).

13. The sterilizer device according to any one of the preceding claims, wherein the distance from the inner surface (304) of the measurement chamber (108) to the open end (124) is at least equal to 90% of a length of a longest tube in a sterilization load in the sterilizer chamber (101).

14. A method of sterilizing a load in a sterilizer device, comprisinginjecting steam into a sterilizer chamber (101);detecting a non-condensing gas inside the sterilization chamber (101) using a first measurement device (110);detecting a a condensation on an inner surface (304) of a measurement chamber (108) that is fluidly connected to an inside of a tube (107) at a distance from an open end (124) of the tube, wherein the tube (107) is inside the sterilization chamber(101);detecting a temperature in the sterilization chamber (101) by a thermometer (306); andgenerating, by a control unit (120), an indication of a sterilization status based on the detected non-condensing gas and the detected condensation.

Images