DE10254446A1 - Sterilization cycle documentation, monitoring and/or validating method for sterilizer for medical products using measured physical parameters - Google Patents

Abstract

The method has the temperature and/or pressure within a sterilization chamber recorded, with evaluation of the obtained temperature and/or pressure characteristic for determining the beginning and end of the sterilization cycle, with delivery of the measured temperature and pressure values for corresponding phases of the sterilization cycle. An Independent claim for a device for documentation, monitoring and/or validating of a sterilization cycle is also included.

Description

The invention relates to a method and a device for recognizing sterilization phases in one Sterilizer by a documentation or monitoring device, in particular this device and this method on a sterilizer as an independent Measured value acquisition in a retrofit device to validate or document the sterilization process of Autoclaves used.

sterilization process

The application of moist heat allows across from dry heat shorter Sterilization times and low temperatures. To all microorganisms kill (including bacterial spores) or the irreversible inactivation of viruses or to reach denatured prions on or in an object, needed one an exposure time. While this time must certain conditions are met - humidity, sterilizing temperature and sterilization time - the Sterilization parameters are called.

• 1 – Entlüftung beziehungsweise Evakuierung der Kammer und des Sterilgutes und Aufheizen des Systems auf die Sterilisationstemperatur (auch bekannt als Vor-Vakuumsphase und Aufheizphase)
• 2 – eigentliche Sterilisation
• 3 – Nachbereitung, Trocknung des Sterilgutes

The steam sterilization process can be roughly divided into 3 phases:

• 1 - Venting or evacuation of the chamber and the sterile goods and heating the system to the sterilization temperature (also known as the pre-vacuum phase and heating phase)
• 2 - actual sterilization
• 3 - Follow-up, drying of the sterile goods

To the formation of air bubbles in the Preventing steam is done first in the chamber of the autoclave a vent (Evacuation of the chamber and the sterile goods), which by various Procedure can take place.

The most common method is currently fractional fore-vacuum processes. The chamber is evacuated several times alternating with steam inflow. Then steam is admitted until the operating pressure is reached.

The residual air is removed the better the vacuum achieved and the higher the vacuum achieved pressure difference is. After this venting phase, use the steam, the sterilization chamber is heated onto the sterilization chamber.

Once the sterilizing temperature the actual sterilization has been reached. she begins with the so-called Compensation time, which serves the temperature differences balance between the sterilization chamber and the items to be sterilized. First now the killing time follows. killing time and a safety surcharge then result in the sterilization time (holding time).

• a. der Ausgleichzeit,
• b. der Abtötungszeit
• c. dem Sicherheitszuschlag

The sterilization phase is composed

• a. the balance time,
• b. the kill time
• c. the security surcharge

After the sterilization time has elapsed the steam is led out of the sterilization chamber and the items to be sterilized dried (drying phase). Usually the sterile goods are included Vacuum dried. The residual moisture (condensate) evaporates and is about the vacuum line led out. The residual moisture content is according to national Standards are set and must not exceed 1% of the original Net weight for laundry or 0.2% for instruments (DIN). The drying time depends on the type of packaging, the weight and the load of the sterile goods.

An example is in 1 the procedure is shown by means of a fractional pre-vacuum (internationally used standard procedure). The figure shows the schematic time / pressure (or temperature) curve during a sterilization cycle. The individual phases explained above are labeled accordingly in the figure.

validation

The validation of sterilization processes will defined by EN 554 as a documented procedure for Providing, recording and interpreting the results that are needed to show that a Procedure constantly conforms to the specified specifications. The validation of sterilization processes is mandatory in the EC area Directive for Medical devices 93/42 EEC required. The EU directive has been around for some Nationally implemented through the Medical Devices Act (MPG). Of there is also the legal one (for example in Germany) Order to the hospitals, patient care according to the state of the art and science guarantee.

The validation of. Described in EN 554 The physical measurement considers sterilization processes as meaningful than the test by means of Bio-indicators. This method of checking the steam sterilization process relies on surveillance physical parameters (pressure, temperature, time, presence of saturated steam conditions), which for sterility of the product are decisive and presupposes that the sterilizer and its installation with a suitable one before validation Specification. Requirements and tests (e.g. testing after installation) for Steam large sterilizers are dealt with in a separate standard, EN 285.

The validation and routine monitoring of the sterilization of medical products is to be regarded as part of the quality assurance of companies producing sterile goods, for example minimum requirements have been set up by the DGKH (cf. Annex 3 of the "DGKH guidelines for the validation and routine monitoring of sterilization processes with moist heat for medical devices").

• – Alle gemessenen Temperaturen müssen innerhalb des sogenannten Sterilisiertemperaturbandes (Sterilisiertemperatur als untere Grenze, +3 Kelvin als obere Grenze) liegen
• – Alle gemessenen Temperaturen dürfen um nicht mehr als 2 Kelvin voneinander abweichen
• – Keine der gemessenen Temperaturen darf um mehr als –/+1,5 Kelvin schwanken
• – Die Ausgleichszeit von 15 s bei einem Kammervolumen von bis zu 800 Liter (30 s bei > 800 L Kammervolumen) darf nicht überschritten werden
• – Die theoretische Dampftemperatur muß innerhalb des Sterilisiertemperaturbandes liegen und mit dem korrespondierenden Dampfdruck übereinstimmen (Sattdampfbedingung)

For example, the following requirements apply to large autoclaves during the sterilization phase:

• - All measured temperatures must be within the so-called sterilization temperature band (sterilization temperature as the lower limit, +3 Kelvin as the upper limit)
• - All measured temperatures may not differ by more than 2 Kelvin
• - None of the measured temperatures may fluctuate by more than - / + 1.5 Kelvin
• - The compensation time of 15 s for a chamber volume of up to 800 liters (30 s for> 800 L chamber volume) must not be exceeded
• - The theoretical steam temperature must be within the sterilization temperature band and match the corresponding steam pressure (saturated steam condition)

documentation the sterilization process

For documentation of the sterilization process by means of physical parameters such as pressure and temperature essentially two systems - internal and external data acquisition devices - used.

An external data acquisition device (e.g. circular chart recorder or line recorder) documented during the entire sterilization cycle the temperature and pressure with independent sensors. The supervision is carried out without contact with the control of the autoclave. In the log the temperature and the Independent printing Sensors are output, but the sterilization phases are not specified made.

The problem here is that according to the national and international standards (EN 554, EN 285) certain parameters while of the sterilization phases that must be observed. For example have to the temperature as well as the chamber pressure at the time of the beginning of the Holding time are documented. Since the sterilization phases in the recorded sterilization cycle are not automatically recognized, it is not possible to find exactly this point in time.

The state of the art also includes internal ones Documentation systems (e.g. batch printer) known by the Control of the autoclave the measured values of the sensors (temperature and pressure) and the timing of the sterilization phases receive. Both the measured values appear on their logs of the sensors, as well as generally the starting points of the sterilization phases. This combination of control and documentation device is however that in the mentioned Independence required by standards both systems questioned.

Furthermore, with autoclaves, the factory over have no documentation system, often no retrofitting possible with a documentation system, because the controls of the devices often no interfaces for it provide.

The object of the invention is therefore in being a simple, inexpensive, automatic and of independent of the control To provide an apparatus and a method for monitoring and ensure validation of the sterilization process. Thus the Requirements for the safety of the sterilization process in particular in the medical field (see EC Directive 93/42 EEC, EN 285, EN 554, prEN 13060ff), especially for surveillance the one for the Sterilization specified parameters met.

This object is achieved by the Features solved in claim 1 and claim 19. Advantageous configurations and further developments are the subject of the subclaims of Claims 1 and 19. Different uses of the method according to the invention and the device according to the invention are in the claims 25 to 28 claims.

The principle on which the invention is based is to recognize the individual phases of a sterilization cycle as well as other points distinguished by the laws and standards mentioned (defined by the temperature or the pressure as a function of time) within these cycles. This detection is realized by analyzing the time / temperature and time / pressure curves recorded during the sterilization cycle. The phases of the sterilization cycle are defined by their start and end points in the temperature and pressure curve (see 1 ).

The venting phase (pre-vacuum) generally begins at the start of the program and includes the excellent times (maxima and minima) of the vacuum phases t (maximum amount of steam burst = start of evacuation) _i and t (maximum vacuum = start of steam entry) _i (see 1 : t _bv and t _bd ).

Sterilization begins with the compensation time when the first temperature sensor in the chamber has reached the sterilization temperature. The holding time begins when all temperatures and the temperature T (p), which corresponds to the pressure due to the saturated steam condition, have reached the sterilization temperature (see 1 t _bp ). The sterilization phase ends when the temperature in the chamber falls below the sterilization band (see 1 t _eh ). This is followed by a steam release and a vacuum is created in the chamber. If the specified Va When the vacuum for the drying phase is reached, the drying phase begins (see 1 t _bt ). It ends after the drying time (see 1 t _et ).

The corner points of the vacuum phases represent local minima or maxima in the course of the pressure curve until the sterilization pressure p is reached (T _{sterilization} ).

The starting point of the sterilization phase is is a local maximum in the temperature curve and pressure curve the sterilization temperature is known, so the invented method recognizes the beginning of the sterilization phase in that a measured Temperature in the chamber has reached the sterilization temperature. The sterilization phase is still due to the plateau in the temperature and pressure curve marked, which is approximately the slope zero has. The method also recognizes the on the basis of this criterion Sterilization phase if the sterilization temperature is not specified is or if several possible Sterilization temperatures (e.g. 121 ° C and 134 ° C) are specified.

The holding time begins when all temperatures and the temperature T _Satt (p), which corresponds to the chamber pressure due to the saturated steam condition, have reached the sterilization temperature. The hold time and thus the sterilization phase end when the temperature in the chamber falls below the sterilization temperature and when the sterilization time has expired. If no sterilization time is specified, the method according to the invention can calculate the sterilization time using the first criterion.

The method according to the invention is thus in able to identify and monitor the sterilization phase.

After the sterilization phase, the steam in the chamber is released and vacuum is drawn. The drying phase begins when a predetermined vacuum value (p _T ) is reached. If the control regulates to a certain vacuum value, a plateau in the pressure curve is again obtained in the drying phase. The system according to the invention determines the beginning of the drying phase from the measured chamber pressure either from the local minimum in the pressure curve, from the plateau (gradient approximately zero) or when the value p _{T is reached} .

Most of the time, the drying vacuum is not regulated, but a vacuum is constantly drawn and a maximum drying vacuum is achieved depending on the vacuum pump and the load. The drying phase and thus the drying time begins when the specified vacuum value p _T (eg 7 kPa) is reached and ends when the chamber pressure rises above this value. In this way, the starting point of the drying time and the associated pressure and temperature values are recorded by the documentation or monitoring device. The end of the drying time is determined by the system in that the chamber pressure passes through the value p _T one last time and then increases until a pressure equalization between the chamber pressure and the ambient pressure is reached.

f(x) gemessener Druck- bzw. Temperaturwert, x Zeit.The method according to the invention calculates the local maxima or minima in the following way:
For a given curve y = f (t), maxima and minima are calculated by searching for zeros of the first derivative y ', at which the second derivative y "is less than zero Pressure in the chamber given by discrete samples replaces the derivative as an approximation of the difference quotient

f (x) measured pressure or temperature value, x time.

This difference quotient is if the measurement curve runs through a maximum or minimum, only very rarely become exactly zero. According to the invention, therefore, the zero crossing of the difference quotient from positive to negative values or from negative to positive values.

In a simplified embodiment, only the difference of the temperature or pressure values or only the sign of this difference is used instead of the difference quotient s to determine the maxima / minima, since the denominator Δx of the difference quotient is always positive in the case of successive measurements, and the difference itself or the sign of the difference is sufficient for a statement about the tendency of the slope (falling / rising). If the sign of the slope changes (or the sign of the difference), a maximum or minimum has occurred (cf. 1 lower curve)

In a preferred embodiment, in order to increase the numerical accuracy, the difference is not determined from immediately successive values but over several sampling intervals. This reduces the influence of fluctuations in measured values due to noise and interference signals (cf. 3 ). The extremum you are looking for is now within this interval and can be found by simple comparison.

Below are more details and Features of the invention using the exemplary embodiments and the drawings explained.

Show it:

1 : schematic representation of a sterilization process

2 : schematic representation of the course of the air leakage test

3 : Determination of the slope over 3 sampling intervals

4 : schematic representation of the Vali scrambling system

1st embodiment

The monitoring system according to the invention has at least one independent temperature and at least one pressure sensor (cf. 4 ). The temperature sensors can also be designed as self-calibrating temperature sensors (cf. applicant's German patent application dated ...). From the start of the sterilization cycle, the monitoring system records the temperatures and chamber pressure measured by the sensors. Based on the above-described detection of the local maxima and minima, the start and end points of the phases (according to temperature / pressure and time since the start of the sterilization cycle) of the sterilization cycle are determined.

Are the phases of the sterilization cycle or the beginning of the individual phases by the method according to the invention have been determined so from the documentation or monitoring device automatically the associated Key points (temperature and pressure as a function of time) are output become. A batch report advantageously contains the measured temperature and pressure values as a function of time and a Statement about when and with what temperature and pressure values the individual phases of the sterilization cycle.

Also, in a preferred embodiment a statement about compliance with the limit values required in the standards. The local maxima and minima are output in the fore-vacuum phase and compared with the specified limit values. For example the minimum vacuum depth (e.g. 3 kPa) cannot be reached be ensured that in the subsequent sterilization process Saturated steam conditions can be achieved. The monitoring system according to the invention so recognize early an error in the sterilization process and gives an error message or stops if necessary the process, if one Interface to the autoclave is available. For monitoring the fore vacuum cycle all maxima (steam inlet height) and minima (vacuum depth) are monitored, to determine and output whether the forevacuum phase was completed correctly is.

Reached after the vacuum phase first temperature sensor the sterilizing temperature (this can be the Enter the user yourself or the default is 121 ° C or 134 ° C), so begins as explained above the balance time. The device according to the invention distinguishes the Compensation time that ends with the last temperature sensor reaches the sterilization temperature and compares this compensation time with the specified limit values. The pressure is here according to the saturated steam condition converted into a temperature and like a measured temperature treated. Is the one prescribed by the standards or by the user Compensation time (for example 15 s a chamber volume up to 800 L, 30 s with a chamber volume above 800 L) exceeded, an error message is again issued because the limit has been exceeded the equalization period in turn indicates that no saturated steam conditions prevail in the chamber or that the load does not follow the sterilization cycle equivalent.

After all temperatures and T _sat (p) have reached the sterilization temperature, the monitoring system according to the invention begins to check the conditions during the killing time. It calculates online the deviations of the temperatures from each other and the fluctuation of the individual temperature sensors during the killing time. In addition, it is checked whether all temperatures remain within the sterilization band. For this purpose, the theoretical steam temperature T _Satt (p) of the chamber pressure is also checked in accordance with the saturated steam conditions. If at least one temperature or T _Satt (p) lies outside the sterilization temperature range, if the measured temperatures do not differ by more than 2 K or if the temperatures fluctuate by more than +/- 1.5 K, an error message can be issued again. as the sterilization conditions, which are prescribed for medical products (see DIN EN 285), are not complied with.

The procedure marks the end of the mortality period in that at least one temperature is below the sterilization band falls and the predetermined kill time (e.g. at 121 ° C: 15 min, 134 ° C: 4 min or defined by the user). All temperatures drop below the sterilization temperature, although the specified kill time has not expired, the end of the sterilization phase is considered defines the point in time at which the first temperature the sterilization belt has left after the start of the holding time. Will a predetermined kill time is not reached, an error message is again issued and the sterilization process may be interrupted.

After the sterilization phase the load is usually dried, possibly only the Steam released in the chamber and so a pressure equalization with the except for Chamber made conditions. The sterilization process would be with that completed.

However, a drying phase usually follows in which a vacuum is created in the chamber. Determined in this phase the monitoring system as indicated above the pressure during the drying phase and outputs it.

If a minimum pressure p _{T is defined} in the chamber during a drying time, the system monitors the drying time from the time at which this defined pressure p _T (eg 7 kPa) was reached in the chamber. If this pressure is exceeded, the system gives the measured by then ne drying time and checks this with any specified drying times.

At the end of the sterilization cycle the system is now able, based on the monitoring described above and control functions (monitoring the sterilization belt, the pre-vacuum phase, possibly the drying phase) to make a statement as to whether the sterilization cycle has run correctly is. It can be output whether all the requirements of the standards Fulfills were (complete assessment: passed / failed).

All monitoring and monitoring described above Control functions of the limit values (monitoring of the sterilization band, the pre-vacuum phase, the drying phase) can also only after recording of the entire sterilization cycle are calculated and output. The advantage of online calculation during the sterilization cycle however, that is still during of the cycle errors and the sterilization if necessary the surveillance system or is canceled by the user.

You can also use the measured values for the temperature and the pressure in the chamber not by the system according to the invention itself, but measured and made available by an external system become. However, this system is the control of the sterilizer must be noted that contrary to the regulations of the standards no independent monitoring of the sterilization cycle.

The excellent values can either be in in tabular form or in a graphically prepared form for documentation and verification purposes.

2nd embodiment

The explanations described above apply to a standard procedure in a steam sterilizer. This is for example described in the standard DIN EN 285. However, it is for certain loads (including liquids) special sterilization cycles are used, the course of which does not coincide with corresponds to the cycle course described above.

The application of the device according to the invention or the method according to the invention also not limited to the process with a pre-vacuum, but can also perform other moist heat sterilization processes, for example after the gravitational process, the steam injection process or Hot air sterilization include.

In these cases, at least one Reference cycle with the monitoring system recorded. New phases are created using the reference cycle and the related ones characteristic points (maxima / minima / limit values such as sterilization temperature, Sterilization pressure / drying vacuum) of the phases defined and also the limits set by the system during which monitors phases should be entered.

When monitoring a sterilization cycle now draws the surveillance system the temperature and pressure values in the chamber as described above and calculates the local maxima and minima and the limit values the phases (e.g. sterilization temperature, sterilization pressure / drying vacuum). It checks this local maxima and minima with those defined in the reference curve Vertices and calculates the respective difference between measured Values and the values in the reference curve. If necessary fits the surveillance system the measured curve due to the deviation from the reference curve (Matching) and compares the measured curve with the reference curve. The curve during however, the hold time is not changed.

Based on the detection of the characteristic Points of the phases become the beginning and the end of the phases from method according to the invention recognized. In a preferred embodiment, by means of this Phase detection in turn monitored, whether the limit values are observed within the phases and whether the sterilization cycle has run correctly.

3.Ausführungsbeispiel

The air leakage test also represents a special form of a cycle that can be monitored by the system according to the invention. According to the standard, this cycle contains the key points t ₀ (start of vacuum generation, starting at ambient air pressure P _u ), t ₁ (p ₁ ) (reaching the vacuum depth of 7 kPa), t ₂ (p ₂ ) (end of the compensation time of 5 min ) and t ₃ (p ₃ ) (end of vacuum test time of 10 min). The monitoring system records the temperatures and pressure in the chamber. If the chamber pressure reaches the vacuum depth of 7 kPa or a minimum in the pressure curve (chamber sealed vacuum-tight), the compensation time starts to be monitored. During this time, the chamber pressure should not rise by more than 2 kPa and the temperature must not deviate from the ambient temperature by more than 20 K. When the 5 min compensation time has expired, the system monitors the vacuum test phase. During this time, the chamber pressure must not rise by more than 0.13 kPa. Of course, other limit values can also be entered and monitored by the operator. If at least one of the specified limit values is not met, the system issues an error message, reports that the air leak test has not been passed and, if necessary, ends the process. A schematic time / pressure diagram is in 2 shown.

In a preferred embodiment, the values recorded by the system for the temperature and pressure in the chamber are encrypted and stored in a database. The batch report and the error messages can be displayed offline or online with the measurement on a screen or a printer or be transmitted via network or signal line to a remote display and monitoring device (control point). This protocol can be used for both verification and documentation purposes.

Claims (28)

Documentation, monitoring or validation procedures sterilization cycles with the following steps:  a) Record of at least one temperature and / or one pressure in a sterilization chamber  b) Determine the beginning and end of the phases of the sterilization cycle due to the course of the measured temperature and the measured pressure in the chamber  c) Output of the measured values for the temperature and the pressure with the corresponding phases in the sterilization cycle. A method according to claim 1, characterized in that the phases by characteristic points such as the sterilization temperature and / or the extremes of the pressure in the Vacuum and drying phases are defined, the most characteristic Points of the measured temperature and / or the measured pressure be determined and based on the characteristic points Phases are recognized. Method according to one of the preceding claims characterized in that in step b) the local extrema of the measured Temperature and / or the measured pressure can be determined. Method according to one of the preceding claims characterized that the recorded temperature and pressure values be compared with limit values specified in the individual phases and an error message and, if necessary, the program is canceled if these limit values are not met. Method according to one of the preceding claims characterized that in the sterilization phase the compensation time and / or in the drying phase the drying time is also specified Limit values are compared and an error message is output and if necessary the program is aborted if these limit values are not be respected. Method according to one of claims 4 or claim 5 thereby characterized as limit values during the sterilization phase a maximum temperature difference between measured temperatures and / or a maximum fluctuation of the individual temperatures and the sterilization belt can be used. Method according to one of claims 4 to 6, characterized in that that as limits for the Chamber pressure during the vacuum phase uses the vacuum depth and the height of the burst of steam become. Method according to one of claims 4 to 7, characterized in that as a limit during the drying phase for a defined drying vacuum is used. Method according to one of the preceding claims, characterized in that the pressure in the sterilization chamber is converted into a temperature according to the saturated steam condition T _saturated (p). A method according to claim 9, characterized in that for the calculated temperature T _Satt p) meets the limit values for a temperature in the chamber. Method according to one of the preceding claims characterized that the measurement of temperature using a self-calibrating probe carried out becomes. Method according to one of the preceding claims characterized that assessed at the end of the sterilization process whether the recorded sterilization cycle or test cycle (air leak test) ran correctly. Method according to one of the preceding claims characterized that a batch record with the values for temperature and pressure in the chamber depending from the time together with the associated phase in particular a printer or monitor. Method according to one of claims 4 to 13, characterized in that that the error messages are printed on a printer or screen become. Method according to one of the preceding claims characterized that the beginning and end of the phases of the sterilization cycle determined online or offline after completion of the sterilization cycle become. Method according to one of the preceding claims characterized that the values for the temperature and chamber pressure in particular in a database encoded get saved. Method according to one of the preceding claims characterized that a reference curve of a sterilization process characteristic points of phases in the reference curve are recorded the measured temperature and / or pressure curve are also defined the reference curve is compared, based on the comparison the characteristic Points of the measured temperature and / or Pressure curve are determined and so the phases are recognized. Method according to one of the preceding claims characterized that in addition the Sterilization cycle is controlled and regulated. Documentation, monitoring or validation device of sterilization cycles to perform the method after a of claims 1 to 18 Device according to claim 19, characterized in that the device in particular has at least one temperature sensor self-calibrating temperature sensor and / or at least one Owns the pressure sensor. Device according to claim 19, characterized in that the measurement of temperature and pressure from an external System, in particular the control of the sterilizer, is carried out. Device according to one of claims 19 to 21, characterized in that that the device contains means for controlling and regulating the sterilizer. Device according to one of claims 19 to 21, characterized in that that a printer and / or monitor is connected. Device according to one of claims 19 to 22, characterized in that that the data are stored in the device, in particular in encrypted form. Use of the method according to one of claims 1 to 18 characterized in that the method on a sterilizer as independent measured value acquisition is used. Use of the method according to one of claims 1 to 18 in the control of the sterilizer. Use of the device according to one of claims 19 to 24 characterized in that the device as an independent measurement value acquisition of a Sterilizer is used. Use of the device according to one of claims 19 to 24 for retrofitting of sterilizers without independent Data acquisition.