DECONTAMINATION
in the tin foil, it is an indication of good ultrasonic activity – in fact, it is quite the opposite. The holes created in the tin foil are as a result of the spikes of sound as shown in graph 1 and, as such, clearly demonstrate erratic dispersion. If spikes are present, there will inevitably be troughs, leading to potentially poor cleaning. Where ultrasonic activity is homogenous, there should be pummelling in the tin foil, but no holes. If holes are present, the system should be considered as not fit for purpose at this level. Through intense experimentation and great assistance from several eminent colleagues, technology is now available that delivers complete protein removal.
Bacteria
But what about bacteria? It was decided in 2018 to engage an outside laboratory to look for and measure any residual bacteria that may still linger on the instrument after processing. The results obtained came as bit of a shock and a further leap in understanding of the relationship between bacteria and protein. The results matrix (Fig 1) highlights what is achieved in terms of bacteria removal following processing in an Advanced Ultrasonic Cleaning System. The laboratory used their own heavily soiled instruments and removed them for measuring immediately after a cleaning cycle at 20°C. What this table of results clearly indicates is that once the protein is completely removed, it is a relatively easy job to remove bacteria with the right chemistry in an advanced ultrasonic tank with homogenous activity.
While disinfection cannot be claimed, as the device doesn’t have a thermal disinfection cycle, the results clearly speak for themselves. A log reduction of 5.5 in cold water. ‘Side effect disinfection’ is disinfection that is achieved, not as not the primary aim of the equipment but as a ‘side effect’ of the protein removal process. Further trials were carried out on ‘lightly soiled’ instruments that returned an average log reduction figure of 6.65, giving further proof of the efficiency of this technology. Several articles have been written about cold sterilisation. Figure 2 shows that it is indeed possible.
What do we mean by advanced ultrasonics? No matter how good, even or aggressive the distribution of sound is, this in itself will not deliver the consistency required for this application. More is needed. The core technology used in the contamination removal process must be supplemented by a suite of additional technologies to ensure that the consistency and performance of the device is maintained. Furthermore, every
JANUARY 2021
aspect of the system has to be monitored as much as possible, from start to finish, not only to ensure compliance, but to reduce theatre-borne infections and reduce the risk to life. With this in mind, every aspect of the device should be monitored to ensure that the system is functioning as it should, with appropriate alarms in place to warn and also cut the electrical supply to the machine if required.
One such aspect, although not stipulated within the HTM 01-01, is the control of biofilm and the negative impact this can have on cleaning performance. During the many trials carried out between 2013 and 2016, it was noted that the first trial carried out after a weekend always rendered poor results. It was concluded that this was in fact caused by biofilm settling on the walls and base of the tank over the weekend (even with the lid closed). We found it astounding that such a small element could affect cleaning in such a way, even after such a short length of time. What this highlighted was that every aspect of the device needed to be exactly right before cycle start if system, and consequently output control, were to be achieved. Recognition and attention to biofilm is a critical requirement in any cleaning device that hopes to deliver the desired results. To avoid the use of foil tests as a means of gauging the ultrasonic output, it is important that, in some way, the core cleaning technology itself should be self- monitoring, with suitable safeguards in place to take corrective action should the generator tuning drift, or a transducer fail, for example. This feature comes into play where lumens and rigid endoscopes are to be cleaned, alongside standard surgical instruments. When validating the ultrasonics, where should the parameters and limits be set? Outside the lumen or inside the lumen? Measuring the ultrasonic activity down the inside of the lumen is an impossibility with a foil test. However, with a CVD, experiments
have been undertaken to determine the losses through the wall of a lumen/rigid endoscope that enable the generator output control system to be set to accommodate this. There are several other inherent features that need to be included within a successful device, which although not directly linked to HTM compliance itself, enable the conditions for compliance. For example, we have known for a long time that ultrasound, when applied into a fluid, actually works at its best during something called the ‘de-gassing phase’. De-gassing of the tank fluid can take a few seconds or several minutes, depending on the watts per litre of sound applied. Active cavitation is a technology that greatly assists with cleaning performance and consistency. Betasound is another technology that delivers the ultimate in even distribution of sound into a tank of fluid.
Protein removal system Ultimately, after eight years of R&D, the result is a fully compliant cleaning device for surgical instruments, lumens and rigid endoscopes.
The design and functionality of Medstar 3 renders instruments and lumens completely protein free to both inside and outside surfaces and has several patented features that enhance the performance and enable compliance with the HTM. It has also been designed to accept robotic instruments. During this period, many discoveries were made which have ultimately led to the development of equipment and technologies that will help improve patient safety and patient outcomes.
CSJ
About the author
Alphasonics’ managing director, David Jones, has a background in design engineering and founded the company in 1993. Alphasonics designs and manufactures advanced ultrasonic cleaning systems, specifically for precision cleaning applications.
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