DE202014009495U1 - Test device for monitoring the sterilization efficiency. - Google Patents

Abstract

Test device for monitoring the sterilization efficiency, characterized in that it consists of a detector arranged in or on a measuring chamber, via a feed line, formed as a physical barrier, preferably a long, tubular metal or plastic compound or a porous body, to the Room of a sterilizer chamber is connected from the outside, the detector distinguishes between water vapor and other gases and sends the measurement result to the sterilizer control.

Description

The invention relates to a test device for monitoring the effectiveness of a steam sterilization process in an autoclave.

For steam sterilization to be successful, the steam must be in direct contact with the item to be sterilized and must contain only small amounts of foreign gases. After EN 285 are just 3.5 Vol.% Foreign gases, based on the condensate allowed. Therefore, before the actual sterilization process, the air must be removed from the sterilizer chamber and replaced with water vapor. This is done by repeated, alternating evacuation of the chamber and rinsing with pure water vapor. Possible air residues can form small islands or pockets in or on the item to be sterilized, which represent an insurmountable barrier to water vapor. As a result, especially in voluminous and porous as well as in long hollow bodies (hoses, endoscopes ...) whole areas remain unsterile. There are several possible sources of foreign gases: inadequate evacuation and purging of the chamber in the starting phase, leaks in the chamber with subsequent air penetration during the vacuum, CO2 formation in the steam generator from salts in the supply water and residual air in porous or elongated hollow bodies of the sterilized material (im further referred to as the "critical Sterilisiergut").

It is known that in saturated steam in a closed container the pressure and temperature are interdependent variables. Therefore, it is checked whether the conditions required for steam sterilization have been reached in the sterilization plant, usually by measuring the two physical parameters mentioned. A sufficient penetration of the steam into the mentioned critical Sterilisiergut is with the s. G. Bowie-Dick test controlled. A chemical indicator changes color when the sterilization conditions are met. The test is usually run once a day as idle. In order to simplify the handling and to be able to carry out the test with every single sterilization run, the classic Bowie-Dick test is increasingly supplemented or replaced by an electronic test.

There are several electronic Bowie-Dick testing devices known. That in the DE 20 2006 006 926 U1 presented system consists of a comparison with the sterilization largely shielded measuring chamber, with a gas exchange between the measuring and the sterilizer chamber is possible. The measuring principle is based on a temperature comparison between the two chambers. Insufficient penetration of the vapor into the measuring chamber is indicated by a lower temperature (a difference of <1.6 ° C is permitted), is assessed by appropriate electronics and further processed as a signal.

In the DE 10 2010 016 017 A1 a device for testing the effectiveness of a sterilization process is shown, consisting of a probe located in the sterilizer chamber and a test body mounted outside the chamber. The measurement principle is also based on the temperature comparison between the sterilizer room and the test specimen.

Also in the US Pat. No. 6,323,031 B1 Bowie-Dick electronic test equipment described is based on the temperature comparison between the sterilizer and the interior of a massive measuring tube, which is closed at one end, while the other end is open to the sterilizer room. During sterilization, the steam flows into the measuring tube, heats its mass and condenses. Contains the vapor foreign gases, they collect in the measuring tube and prevent the temperature compensation. An evaluation unit evaluates the measured values and forwards the corresponding signals to the sterilizer.

There are also a number of different systems for assessing sterilization effectiveness, such as U.S. Patents 4,115,068 . 5,066,464 . 5,270,217 , In all, the vapor must pass a physical barrier before entering the measuring device, usually a long capillary or tube, an open-pore polymer foam, etc. The measuring principle is generally based again on the temperature comparison between a measuring chamber and the sterilizer room.

Disadvantages of the known electronic systems for controlling sterilization effectiveness:

All test devices described are based on temperature measurements. In steam sterilization, not only temperature, but also humidity plays a decisive role. To achieve the same sterilization effect with hot air, it is known that it requires significantly higher temperatures and longer exposure times. The temperature sensors of the known devices can not distinguish between water vapor and air at the same temperature. It is quite conceivable that in a continuous operation of the sterilizers, the known test devices are heated to such an extent that the air in them does not fall below the permitted lower temperature limit and the system fails. For this purpose, some investigations have already been carried out, such. B. F. Benoit et al .: "In comparison: Four devices for electronic Verification of steam penetration according to ISO 11140, Part 4. ", Zentralsterilisation 3/2011, S. 174-179 , and Van Doommalen et al .: "Pressure and temperature measurements alone are not sufficient to monitor steam sterilization - a case study", Zentralsterilisation 4/2014, p. 246-248 , Both authors conclude that the measurements of pressure and temperature alone are not always sufficient to assess conditions in steam sterilization. It is required that the test equipment should be capable of switching between steam and other gases, e.g. B. to distinguish air.

Another disadvantage of the known electronic test equipment is the need for a certain amount of electronics. At least two precisely calibrated temperature sensors (often several and additionally a pressure sensor) must be monitored and their values compared with stored data and evaluated. The regular maintenance and calibration of the devices is time and cost intensive.

In the mentioned, known, electronic Bowie-Dick testing devices, the result of the test is known only at the end of the sterilization process, it would be desirable during the process to abort the further course of time and save time and energy.

The present invention has for its object to provide a simple and inexpensive tester for safe control of the effectiveness of each sterilization process so that the specimen between water vapor and other gases or between steam and air directly different, instead of based on temperature measurements.

This object is achieved with the test device according to the invention, which consists of a vapor or a gas detector, arranged in a measuring chamber which is connected via a physical barrier, preferably a metal capillary or a hose, with the space of the sterilizer chamber. The detector according to the invention can distinguish between water vapor and other gases or between water vapor and air. Various principles can be used for this. The preferred solution uses the different light absorption properties of the media to be measured. Even in the saturated state, water vapor is a colorless, completely transparent gas which has several absorption maxima, especially in the IR light range. In the tester according to the invention, a wavelength is used in which water vapor has an absorption maximum and at the same time absorb the air and the other gases in question as little as possible, preferably between 1400-1600 nm. The detector works on the principle of specific light absorption practically as a light barrier A light source, preferably an LED or a laser diode, transmits through the volume of the measuring chamber an IR light beam of selected wavelength, which is measured in intensity after passing through a photodetector. If there is water vapor in the measuring chamber, the light beam is absorbed - the photodetector delivers no signal. If there is air in the measuring chamber, or other gases without water vapor, the light beam passes unhindered, and the photodetector provides a signal. The light path must be so long that the absorption by the water vapor is only sufficient at an absolute pressure> 1.8 bar, in order to deliver a safe measuring signal. In addition, a threshold value can be entered in an integrated evaluation unit, in which the measurement signal can be assigned to a critical water vapor concentration value which is to be monitored for overshoot. The evaluation unit communicates with the sterilizer control.

The measuring chamber has as input a long and narrow tubular inlet made of metal or plastic, which allows a connection with the space of the sterilizer chamber and simulates the difficult to sterilize conditions. The supply line is dimensioned and arranged so that the condensate can flow into the sterilizer room without hindering the further supply of steam. Various designs are conceivable, some examples are explained with reference to the figures.

It shows:

: Schematic structure of the test device according to the invention for monitoring the sterilization efficiency.

, Another embodiment of the test device according to the invention for monitoring the sterilization efficiency.

Example of a further embodiment of the test device according to the invention for monitoring the sterilization efficiency.

shows the schematic structure of the test device according to the invention for monitoring the sterilization efficiency. The test chamber 2 The tester communicates with one end via a hose or metal tube 1 with the room of a sterilizer chamber (not shown), the other end is closed. On opposite sides of the test chamber 2 there is a light barrier, consisting of the light source 3 and a photocell 4 , The body of the test chamber 2 consists of a heat-resistant and transparent to the wavelength of light used plastic or glass. A ray of light (dotted arrow line 5 ) is from the photodiode 4 detected, the measured value is over the line 6 an evaluation unit 7 fed, and as a signal over the connection 8th passed on to the sterilizer. The hatching in the supply line 1 symbolizes the water vapor, denoted by D, the area L represents the proportion of residual air. The entire photocell can along the test chamber 2 in the direction of the arrows 11 to be moved. As a result, the limit to the permitted amount of air can be adjusted and the tester calibrated. At the supply line and / or at the measuring chamber can additionally a thermally effective mass 9 or cooling fins 10 be mounted so that more vapor condenses in the tester and transported air into it - this type of supply line is known from the prior art. During operation, in the test device, as well as in the sterilizer chamber, the air should be replaced by water vapor. The long and narrow supply line simulates the above critical items to be sterilized, which is difficult to vent. In case of unsuccessful or incomplete venting remains in the test chamber 2 or in their final volume some residual air. The presence or absence of the air (or other gases except water vapor) is detected by the detector as described above. The evaluated signal is forwarded for output to the sterilizer control, but can not be changed by this.

shows an example of another embodiment of the test device according to the invention for monitoring the sterilization efficiency. To reduce the temperature load on the sensor optics, located between the test chamber 2 and the photocell (consisting of the light source 3 and the photodiode 4 ) a light guide 15 and in the test chamber 2 is a light reflector (mirror) 12 , Another advantage of this design are the smaller dimensions that are made possible by the double light guide. The test device can be connected 1 connected to the sterilizer, as with the described, or be included directly in the sterilizer chamber or in its own, communicating with the sterilizer pressure body. The sterilizer or pressure-body wall is connected to the line 13 indicated. In this version, the supply line 1 and at least part of the test chamber 2 also exposed to the water vapor from the outside. The light guide 15 , a glass rod or fiber optic, is with the O-ring 14 sealed and prevents heat transfer to the optics. Other parts or numbering correspond to the ,

In the is a further example embodiment of the test device according to the invention for monitoring the sterilization efficiency shown schematically. It has a similar structure to the ones below described the connection 1 to the sterilizer is but to the test chamber 2 connected laterally. This solution allows the attachment of the reflector 12 on the adjusting screw 16 , so that a Einjustierung the light path length is possible. Other parts or numbering correspond to the and ,

In the test device according to the invention, other sensors for distinguishing between water vapor and air can be used to monitor the sterilization efficiency instead of the described light absorption method. Particularly suitable for this purpose are oxygen ultrasound and special moisture sensors. Suitable oxygen sensors are available on the market, but cost so far about 10 times the light barrier. Ultrasound and humidity sensors would have to be adapted or newly developed for the purpose first, but measuring methods are in principle suitable for this purpose.

Advantages of the test device according to the invention for monitoring the sterilization efficiency compared to the current state of the art:

The test device according to the invention can distinguish water vapor from other gases, is thus ideally suited for the purpose. The well-known s. G. electronic Bowie-Dick test equipment can not distinguish between water vapor and air, the commonly used temperature difference measurement method is unsuitable. Thus, the known test equipment can cause misjudgements that could have fatal consequences in healthcare.

• 1. Als Prüfgerät zur Dampfdurchdringung
• 2. Als Prüfgerät der Dampfqualität.
• 3. Als Universalprüfgerät für die gemeinsame Überwachung der Dampfdurchdringung und der Dampfqualität.

The sterility effectiveness monitoring device according to the invention can be used in three different ways:

• 1. As a test device for vapor penetration
• 2. As a tester of steam quality.
• 3. As a universal tester for joint monitoring of steam penetration and steam quality.

No previously known testing device can fulfill all three mentioned application possibilities.

The test device according to the invention works with each sterilization batch and not just once a day, or after hours cooling down, as the devices of the prior art. Another advantage is that a faulty sterilization is already detected during the process - it can then be interrupted in time and not only after the complete process, as in most known test equipment. This saves time and energy and protects the system.

Depending on the design can with the test device according to the invention in a faulty Sterilization the cause of the fault can be identified immediately, whereby the necessary countermeasures can be taken without loss of time.

Another advantage of the device according to the invention is the very simple production, function, and low production and operating costs.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 202006006926 U1 [0004]
• DE 102010016017 A1 [0005]
• US 6323031 B1 [0006]
• US 4115068 [0007]
• US 5066464 [0007]
• US 5270217 [0007]

Cited non-patent literature

• EN 285 [0002]
• F. Benoit et al .: "In comparison: Four devices for electronic verification of vapor permeation according to ISO 11140, Part 4.", Zentralsterilisation 3/2011, S. 174-179 [0008]
• Van Doommalen et al .: "Pressure and temperature measurements alone are not sufficient to monitor steam sterilization - a case study", Zentralsterilisation 4/2014, S. 246-248 [0008]

Claims (14)

Test device for monitoring the sterilization efficiency, characterized in that it consists of a detector arranged in or on a measuring chamber, via a feed line, formed as a physical barrier, preferably a long, tubular metal or plastic compound or a porous body, to the Room of a sterilizer chamber is connected from the outside, the detector distinguishes between water vapor and other gases and sends the measurement result to the sterilizer control. Test device according to claim 1, characterized in that the test body is wholly or partly in the sterilizer chamber and the measuring signal is fed via a line to the sterilizer control. Test device according to claim 1, characterized in that the test body is wholly or partly in the sterilizer chamber and contains a data memory in which the measurement signal is stored. Test device according to claim 1-3, characterized in that the detector is a light barrier whose wavelength is in an absorption maximum of water vapor or in its vicinity and is not or only slightly absorbed by other gases. Test device according to claim 4, characterized in that the light beams between the detector and the measuring chamber are guided over a light guide. Test device according to claim 1-3, characterized in that the detector is an oxygen sensor which monitors the oxygen presence or absence. Test device according to claim 1-3, characterized in that the detector is an oxygen sensor, which extrapolates its measurement result to the corresponding amount of air. Test device according to claim 1-3, characterized in that the detector is an ultrasonic sensor. Test device according to claim 1-3, characterized in that the detector is a humidity sensor. Test device according to claim 1-3, characterized in that the detector is an opto-acoustic sensor. Test device according to one of the preceding claims, characterized in that the detector is arranged on the measuring chamber from the outside, and the measurement is carried out through the walls of the measuring chamber. Test device according to one of the preceding claims, characterized in that the measuring chamber is the end piece of a tube closed at this end, along which the detector can be moved. Test device according to claim 5, 11 and 12, characterized in that the light barrier is designed as a reflector-light barrier, with at least two times passage of the light beam through the measuring chamber. Test device according to claim 13, characterized in that the reflector of the light barrier is arranged adjustable, so that the path length of the light beam can be adjusted within the measuring chamber.

Images