Impingement Washing
High Impingement Washing Represents 60% of the Cleaning Process
Standard washers most utilized in hospital decontamination departments, be it a tunnel washer or single chamber, rely on high impingement to complete the washing process. Impingement is best defined as the mechanical action of pressurized water forced through spray jets to remove debris.
The relative efficiency of a washer/disinfector is approximately 60% as a result of the mechanical impingement action of forced water delivered by spray arms. A failure in any one spray arm will effect the washers overall ability to clean the instruments. The remaining 40% is dependent on a number of factors related to chemical and thermal actions that cannot self adjust to respond to failure of the spray arms.
One of the few articles on impingement - www.steritecproducts.com/PDF/
Impingement Must Be Directed To The Contact Surface
40% Chemical / Thermal / Human Factors
- Cold and hot water hardness / temperature
- RO water purity
- Enzyme dilution
- Detergent dilution
- Lubrication dilution
- Rinse cycle
- Metal mass
- Placement or positioning of instruments
The Contact Surface is the Serrations, Teeth, and Hinged Areas - The Tissue Surface Areas
One attempt to solve poor positioning is the 5-inch stringer; when used properly instruments are in an up-right position which greatly improves the washer impingement process.
However, layering becomes a challenge when instruments are strung with no space between each one resulting in reduced surface contact with all cycles in the washer.
Overloading the stringer makes things even more challenging in that there are no limits to the number of instruments other then the length of the stringer.
When compressed to fit that last instrument water flow becomes a problem inhibiting the overall washing process.
In an up-right position impingement will improve flow to allow drainage
Additionally improper placement of instruments and poor rack selection will further reduce the impingement process. The closer the instrument is to the spray arm or impingement action in an upright position the better the final results will be.
Making things even more difficult for automated washers is that there are no defined load limits or configurations….let alone studies to support the process pre and post washer.
Laying down or on the side elminates the target surface
Washer racks come with a number levels resulting in varying distance from the spray arm. The farther the distance the less effective the impingement becomes.
Keep in mind, as water falls from level to level it interferes with the spray arms water impingement due to re-direction caused by increased volume resulting in a splash affect. Simply put, water volume increases as it drops from each level.
Overloading the second, third, forth, or fifth level can have decreased impingement due to increased masses of instruments and poor placement on each level.
For best performance place smaller sets on lower levels.Moreover, the more levels the more spray arms, which results in additional maintenance and a higher potential for failure and decreased impingement.
Staining and Spotting is Directly Related to Poor Cleaning Processes
Along with positioning of instruments a poor manual pre washer process can over challenge the washer’s impingement abilities; more so when there are no established load limits.
Moreover the manual pre-washer process starts in the surgical suite and moves to decontamination. More importantly the focus is the removal of visible bio-burden starting at the point of use. The more effective this process is the better the final results.
As with all related potentials for exposure the manual process must be followed to insure employee safety. However, there are few if any hospital based studies that measure bio-burden reductions levels at every phase of the process, skipping any one step can affect the outcome.
Short cuts occur more often then not when the pressure is on to keep up with room turnover and there is lack of instrument inventory to support the daily OR schedule.
Washers cannot adjust to poor manual processes nor can they measure the number of instruments in a cycle or given level of bio-burden on them. If the manual process is reliant on speed the out-come can become a disaster. Speed kills when it comes to instrument management and turnover.
Mistakes, repairs, and replacement costs increase resulting in poor final results which is not what we as CS professionals want to put our names on. High flash sterilization utilization is the first indicator that short cuts are taking place—this along with low inventory and poor instrument management.
The Proper Rack Selection is Key
Rack Selection is Key to Efficient Through-Put
When making the choice for instrument racks the 3-level provides optimal performance while maintaining volume and throughput. Four and five level racks add time to loading and can slow production due to increased wait time both pre and post washer.
Sending a 4 or 5 level rack through the washer half empty defeats the purpose of increased volume, which is the only reason for purchasing one.
The Cradle Opens the Target Surface to Allow Full Impingement to the Target Surface
A plugged or leaking spray arm reduces impingement for each level of the washer.
When a spray arm on a 3-level washer rack is not functioning it will reduce the overall washer ability to produce high-impingement by as much as 20%. When spray arms are plugged or a bushing has failed the results are insufficiently washed instruments.
Glass doors and lighted chambers on most automated washers allow some visual ability to view the washer’s process and spot spray arm movement.
The Closer the Better
Impingement efficiency as previously mentioned is dependent on contact to the primary surface area which is directly related to the placement and positioning of instruments.
Surgical instrumentations primary area is the surface that has the highest contact with human tissue including hinged and uni-body areas. High Impingement is more successful when direct contact can be made on the targeted surface.
Positioning of instruments becomes even more challenging when the quantity or mass of instruments exceeds the washer’s ability and there are no limits set. Piling of instruments is one area that affects the impingement process as well as poor rack selection and layering.
Using perforated bottom flash pans with solid stainless steel sides also reduces or redirects impingement as will the use of hold-down screens.
Rack mounted spray arms which have jets aimed both up and down cannot complete direct upward contact to the vital instrument surfaces when perforated bottom trays as used.
Mesh bottom trays however allow for better flow but pose other problems when instruments become logged in the wire sides and bottoms. The trade off has yet to be measured.
Final rinse cycles remove residual chemicals and debris that piling and poor placement inhibits.
The Closer the Instrument is to the Impingement Action the Better the Final Product - Distance and Positioning
Unfortunately the washers do not self monitor the spray arms or provide alarms to alert failure. Staining and spotting of surgical instruments is directly related to poor manual washing processes and the lack of routine washer preventative maintenance.
As previously discussed, a poorly maintained washer cannot counter a poor manual process nor can the washer adjust to increased masses of instruments or bio-burden. Routine spray arm parts should be part of the decontamination inventory as well as routine spray arm maintenance.
With older washers the spray arms need to be checked daily and in some cases per shift; higher the volume the more critical the need for preventative maintenance to insure high-impingement and a consistent processe.
