Developing a Flexible Endoscopic Pre-cleaner/Fluid Dispenser
Tracing a project - development of a device to assist in processing endoscopes for reuse.
| The device uses commonly available technogy and is not patented as market size is small. Rather this is published as an aid to further discussion and development. |
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Pre-cleaning before sterilizing/disinfecting |
The Process Overview
Endoscopes are diagnostic tools that enable the specialist to see inside patients. They use fibre optics for illumination, visual and video imaging. They also contain hollow channels (lumens) for pressurizing, dosing and sampling. All surfaces, inside and out must be cleaned and sterilized between patients. Endoscopic instruments are cleaned and sterilized according to hospital protocol, which varies widely between institutions. Generally, cleaning and sterilization time is limited by the need for re-use on the next patient. A combination of techniques is used to achieve a quick safe and effective turnaround, at a level lower than absolute sterility which may be achieved by longer methods taking several hours.
The Procedure Focus
The initial and most important step of reprocessing is thorough cleaning to remove gross soil, including microorganisms (bio-burden), which then allows the disinfectant or sterilizing agents to work effectively. If an instrument is not cleaned properly, it cannot be sterilized or disinfected. The dispensing device is used as one of the tools in this process.
Typically a procedure for pre-cleaning endoscopes includes:
1. Removal of the soiled endoscope from the patient
2. Rinsing the soiled instrument in a sink with a copious amount of water and wiping down the outer sheath with a single use paper or non-woven fabric wipe
3. Brushing internally while the endoscope is immersed in an enzyme detergent bath
4. Rinsing the endoscope lumens with water using a large syringe or other water jet
5. Rinsing the instrument and the hollow channels with water and then air flushing to substantially dry the surfaces in order to avoid dilution of disinfectants in the sterilizer
The endoscope is then ready for disinfection or sterilisation in a processor such as a Steris Processing System see Steris SYSTEM 1® Sterile Processing System.
Upon removal from the sterilizer, the endoscopes are dried and hung in airing cabinets, ready for reuse.
The Manual Procedure
At Flinders Medical Centre, manual procedures for cleaning endoscopes before automated sterilisation include brushing and syringing the lumens. After brushing, a syringe is loaded with the cleaning solution, and injected into the ports. It is left to soak. The operator then syringes each port with air, then water then air again. On some endoscopes, the cleaner can perform 18 syringing operations before sterilization can begin.
Typically at Flinders, staff will repeat this cycle 15 to 20 times a day, yielding hundreds of fill and empty cycles of the syringe. Because of the small bore of the endoscope lumens, flow of cleaning fluid from the syringe is restricted so the operator must apply a higher pressure. This is compounded by the use of large syringes to hold sufficient fluid for an endoscope, so the force the operator must apply is increased by the ratio of the larger area of the plunger compared to the bore of the tubing. Additionally static friction within the syringe bore increases as the diameter increases.
The Project Stimulus
Complaints of tendonitis and inflammation or aggravation of arthritic joints have been received at Flinders OHS. Repeated use of the syringe in requiring excessive force was found to be stressful. Some staff were facing redeployment because of their chronic injuries, or were restricted in their duties to avoid further aggravation of their developing conditions and in one case were wearing prescribed wrist/thumb splints. It is possible that a worker's ability to apply sufficient pressure waned towards the end of the day as inflammation set in (not verified).
The Options
Flinders Biomedical Engineers were asked to assist. Options considered included:
• smaller syringes.
• a lever device to operate the syringe.
• a foot pedal squeeze bulb.
• a bench top pump.
• an automated pneumatic device.
• an automated electronically controlled pneumatic device.
Practical and useful criteria requirements for the Endoscopy Pre-Cleaner/Dispenser were determined:
1 Eliminate syringe use.
2 Consistent pressure profiles applied to endoscope.
3 Ease of use.
4 Easy to maintain, sterilize parts, replace tubing.
5 Able to adapt existing connectors to this pre-cleaner.
6 Quiet operation -Noise had been an OHS issue in the Flinders old reprocessing room.
7 Automation. Reduction in staff time required to work on the endoscope, can potentially do secondary jobs while observing automated dispenser activity. (Staff are still responsible for seeing the dispenser functions correctly and the resulting standard of work.)
The ideal was seen as total removal of the need for syringes and the electronic option using wall gas was chosen. A prototype two port outlet design was built as it would cover most of the endoscopes in use.
The Device
The device dispenses fluids to the endoscope being cleaned by driving it with 100kPa to 130kPa, (15 -20PSI) gas supply and opening and closing pinch valves in a programmable sequence at set times.
- The operator is responsible for observing the correct function of the dispenser.
- The dispenser uses a regulator fitted to a dry medical air pipeline outlet or dry medical air cylinder.
- Regulated air pressurises two 6 litre pressure vessels which hold the enzymatic cleaning solution and water for flushing.
- The regulator is set within the endoscope manufacturer's maximum pressure specifications.
- Overpressure safety relief valves are fitted to the regulated air supply, and pressure vessels (30 to 40 PSI)
- The dispenser automated fill, soak, and flush times can be adjusted by programming. A typical complete endoscope pre-cleaning cycle takes 5 to 10 minutes.
- The device runs on a low voltage power supply for use in wet areas and uses a programmable relay controller to perform the control functions.
- Software prepared using Möeller 'Easy-Soft6 Pro'
- Downloaded via serial cable from PC, or can be manually programmed.
- Air usage is small and depends on programmed flush times.
- Safety equipment must be used - eye protection, gloves and apron.
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Cleaning Fluid Dispenser |
The Results
The Prototype functioned well, and a second unit was built when the second Endoscopy theatre came into regular use.
What is good
- The users received the device with gratitude, and after two years of use are just as enthusiastic.
- The users found the device simple to use.
- The device was generally reliable up to the two year mark. On a few occasions, 30 endoscopes have been processed in one day, typically 15 to 20 per day using just one dispenser.
- Flushing and soak times were able to be adjusted as required (easy laptop adjustment)
What is not so good
- Faults for the two units over the two year period have required replacement of 4 pinch valves, one power supply upgrade on the prototype, and one cable plug.
After about 18 months we had one pinch valve fail to operate correctly, and started to think about alternatives. After the two year mark, three more failed in quick succession, usually not closing fully, and one failing to open, which required an endoscope to undergo a repeat procedure. Three of these valves showed external signs of corrosion though care had been taken to seal the metal casings inside the enclosure with only the teflon component exposed. The stiffening of the actuator movement was likely caused by corrosion in all faulty valves. As a result we are now moving to solenoid operation where the solenoids and manifold are completely enclosed in a waterproof box.
Precautions
Infection control is an ongoing issue where devices are used repeatedly on patients. The dispenser is part of the cleaning cycle, and should not be a source of contamination in the event of failure of the final sterilisation process. Therfore it is included in the institution's contamination monitoring regime. The fluid components are swabbed regularly for laboratory analysis along with pertinant parts of other devices used in reprocessing flexible endoscopes.
An infection control procedure has been established for the device.
Safety
Gloves, eye protection and apron are recommended in the flexible endoscope reprocessing environment, where sterilizing and flushing fluids, compressed air, hot water etc. are generally found. These precautions also apply to the dispensing device.
Significance
Endoscope pre-cleaning uses manual processes that may lead to overuse injury. Many hospitals in Australia and around the world use similar pre-cleaning regimes. Manual pressure is applied to a syringe to force fluid through the thin cannula of an endoscope. Repeated strain injury may occur when the work load is high.
FMC endoscope cleaning staff have developed overuse injury. After one month of running the prototype in the Flinders Endoscopy suite, staff have expressed their gratitude. Syringing operations have been reduced to less than 10% of the previous work load, and no longer present a problem. Anecdotally there is no inflammation or pain evident at the end of the day and the need of anti-inflammation drugs by an individual was eliminated. Normal duties have been resumed by those who were previously restricted, and extremes of management by redeployment are no longer necessary. Potentially staff turnover is reduced.
The device occupies a niche market as an aid to the manual pre-cleaning of endoscopes, and so complements the use of endoscopic reprocessing sterilizers/disinfectors, which generally work by placing the endoscope in a sealed cabinet, with sprayers and the like to sterilize the outside, and all lumens connected to pumped fluids. See Steris System 1
Where to next?
Enquiries have been received from several hospitals, but distribution off site has not been undertaken while the reliability and potential problems were being evaluated.
A design with internal solenoids rather than pinch valves is underway.
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