High Impingement Washing: A Vital Part of the Instrument Management Process


Most, if not all, of the washers utilized in today’s hospitals rely on high-impingement washing action to complete bioburden reduction levels that allow safe handling of instruments prior to sterilization. However, high impingement was not exclusively developed for the decontamination of surgical instrumentation in hospitals. From home dishwashers to car washes, high impingement is employed in many ways by means of water, chemicals, solid material and air.

Complete a Google search of “high impingement” and you will find more than 3 million pages. Buried somewhere in the information highway is little mention as to the significance this process plays in today’s decontamination of surgical instruments. Instrument washers, both single chamber, tunnel, and cart washers, rely on the water impingement as part of the disinfection and cleaning process. Furthermore, impingement classifications that apply to surgical instruments can be defined as followed: The mechanical process of a cleaning solution striking a surface. Impingement usually occurs in a spray process, and helps dislodge soils from surfaces. A process resulting in a continuing succession of impacts between (liquid or solid) particles and a solid surface.

Impingement is best described in a hospital decontamination setting as the mechanical action of pressurized water forced through spray jets to remove debris. High impingement is achieved by means of forced water through water channels which are then directed to spray arm jets by utilizing high-pressure water pumps. The relative efficiency of a washer/disinfector’s mechanical impingement action is between 50 percent to 60 percent of forced water delivered by the spray arm’s jets.

Consequently, a failure in any one spray arm will affect the washer’s overall ability to clean instruments. Spray arms typically spin in a clockwise direction on all levels, with directional jets on opposing arms. Most rack-mounted spray arms have jets on both top and bottom, while the machine mounted arms spray in one direction — up or down.

Additionally, the remaining cleaning process is about 40 percent dependent on chemical, thermal and human factors related to processes that cannot self adjust or respond to a failure of the spray arm(s):

• Cold and hot water hardness

• Water temperature

• Enzyme dilution

• Low alkaline detergent dilution

• Lubrication dilution

• Rinse cycle

• Reverse osmosis water purity

• Metal mass

• Placement of instruments

• Layering

• Poor routine maintenance

• Improper rack selection

• Overloading

• Bioburden level and location

• Target surface

Spray arms mounted both in the washer and on the selected washer racks complete a circuit. A decrease or loss of pressure in any one spray arm will reduce the overall impingement process. One way of understanding this is to picture a standard sprinkler system for watering your yard; lose a sprinkler head and watch what happens. Leaks in most, if not all, water systems result in reduced pressure; high-impingement washers rely on just that — sustained pressure.

Moreover, the closer the instrument is to the spray arm or impingement action in an upright position, the better the final results. Making things even more difficult for automated washers and central service professionals is that there are no defined load limits or configurations, let alone studies that measure and support the process pre- to post-washer.

Instruments’ Positioning Has Effect on Impingement

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 instrumentation’s primary area is the surface that has the highest contact with human tissue, including hinged and unibody 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 are used. Mesh-bottom trays, however, allow for better flow but pose other problems when instruments become lodged in the wire sides and bottoms. The tradeoff has yet to be measured.

Layering occurs when utilizing a single-level, general-purpose rack with instruments placed in a flash pan and adding a hold-down screen; this reduces or redirects the water spray resulting in splash rather then a cutting action. Poor positioning affects all cycles, including the final rinse, which is the last and most important cycles in an automated washer. Final rinse cycles remove residual chemicals and debris that piling and poor placement inhibits.

Stringing Instruments and Impingement

One attempt to solve poor positioning is the five-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 it. When compressed to fit that last instrument, water flow becomes a problem, thus inhibiting the overall washing process.

Along with size configurations of each type of instrument and what constitutes a proper opening, stringing has some limitations. A ring-handled instrument’s optimal opening is about a 90-degree angle, which allows flowthrough the box-lock area. A nine-inch instrument's box-lock surface area cannot be opened to the same distance/angle as a five-inch instrument on the same size stringer. Laying the stringer on the side completely eliminates the target area of the instrument, namely the box-lock and tissue contact area serrations or teeth.

Where this was a great first step at addressing the positioning problem, it added additional processing time. If you pre-string, then you must have a well-defined manual process, starting in the operating room, with soaking and removal of gross visible bioburden. The angle of the stringed instruments must be standing upright, following the stringer manufacturer’s recommendations to allow impingement contact and flow for optimal results.

Washer Rack Selections’ Effect on Impingement

Washer racks come with a number of levels, resulting in varying distance from the spray arm. The farther the distance, the less effective the impingement becomes. Keep in mind that as water falls from level to level, it interferes with the spray arm’s water impingement due to redirection caused by increased volume resulting in a splash affect. Simply put, water volume increases as it drops from each level. Overloading the second, third, fourth 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.

When making the choice for instrument washer racks, the three-level rack 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 four- or five-level rack through the washer half empty defeats the purpose of increased volume, which is the only reason for purchasing one.

The two-level rack in most washers is designed for instruments on the top and basins or pans on the bottom. Distance of the spray arm from to the target surface on the bottom is more suited for larger items. Impingement is reduced as a result of the distance, producing a splash effect more so than a cutting action achieved on the first level. The closer the better applies in most, if not all cases.

Manual Process Effect on Impingement

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 bioburden, 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 ensure employee safety. However, there are few, if any, hospital-based studies that measure bioburden-reduction levels at every phase of the process; skipping any single step can affect the outcome. Shortcuts occur more often than not when the pressure is on to keep up with operating room turnover and there is lack of instrument inventory to support the daily schedule.

Washers cannot adjust to poor manual processes nor can they measure the number of instruments in a cycle or given level of bioburden on them. If the manual process is reliant on speed, the outcome can be 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 CS professionals want. High flash-sterilization utilization is the first indicator that short cuts are taking place; this along with low inventory and poor instrument management.

Rack and Placement Improvements

Newer, faster washers have entered the market, only to run into the same old problem of positioning and load limits. One thing missing from our washers is the ability to place instruments in an upright, open position, allowing full impingement and flow to the target surface. Home dishwashers provide a visual example of how best to position items; plates, cups, forks, knives and spoons are in an upright manner, allowing full washer impingement and drainage.

Missing from the healthcare instrument washers is just that — a racking system to complement the impingement process by placing instruments in an upright position closer to the spray jets’ cutting action. More recently a new product, the instrument cradle, was introduced into the decontamination market to address this problem. Designed around a coil spring, the cradle improves placement awhile complimenting the overall impingement action for ring-handled and non-hinged instruments.

With its coil-spring design, instruments receive full impingement, including improved drainage and faster cooling while allowing full visibility on the assemble side — resulting in quicker turnover time. Additionally, with the improved drainage there is less spotting, faster cooling and cleaner instruments. Final rinse cycles are greatly improved for all types of ring-handled instruments, including delicate cardiovascular and ophthalmic instruments.

Maintenance and Impingement

A plugged or leaking spray arm reduces impingement for each level of the washer. When a spray arm on a three-level washer rack is not functioning, it will reduce the washer’s ability to produce high impingement by as much as 20 percent. 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. 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 bioburden. 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 preventive maintenance to insure high impingement and a consistent process.

Testing the Washer Cycle

One positive aspect of the process is the ability of the CS technician to test or challenge the washer cycle. We now have a number of washer tests in today’s decontamination arena, with more on the way. Each one gives us an extra tool to identify problems before they become disasters. Along with a well-written service contract, today’s washer tests give us an additional tool to ensure patient and employee safety while providing some form of cycle validation. We have been QA testing the sterilization process for years, now we can do the same for the washer and even the sonic. Where the sterilizer relies on several phases to complete sterilization, so too does the instrument washer.

The washer’s operator’s manual provides added recommendations to support routine maintenance. Establishing a daily closing procedure improves washer outcomes. A closing procedure that includes washer screen cleaning and general spray arm evaluations will maintain the washers’ ability to complete high-impingement instrument cleaning. An opening procedure as a secondary follow-up will insure compliance and further the importance of the QA process. A well-written service contract with quarterly preventive maintenance, along with daily washer QA, supports a standard of care in keeping with the daily sterilizer testing.

Detergents and Chemicals’ Effect on Impingement

Where routine maintenance is important, so is the selection for detergents and chemicals to support impingement. Some manufacturers of automated washers only endorse the use of products developed for their equipment. Enzymes and detergents react differently depending on several factors, and in most cases, the device manufacturer’s products work best because of extensive testing on their part. Water hardness can play a key role as it functions with various chemicals as will a number of other factors including dilution rates; too much is just as bad as too little.

Depending on where you live, the water mineral make-up will determine additional steps to insure chemical to water ratios. Rinse cycles become even more important when poor water conditions exists. Hard water conditions increase the need for routine washer descaling that can affect spray arms by plugging up the jets. Visual white scale on the bottom of the outer door is one indication that hard water is a problem.

When this occurs, descaling must become a routine program, to include rack rotation, so that all receive the same attention. Too often the lowest bidder gets claim to which chemicals are used by CS professionals – this should never be the case when the end results matter so much. You may save a nickel but you will pay a dime to fix picking the wrong soaps and enzymes for your instrument decontamination management process.

Future Requirements to Improve the Washing Process

Perhaps one day in the future, washer manufacturers will develop spray-arm sensors to alert a failure, stopping the cycle rather than allowing it to proceed. Developing load limits and improved racking systems in keeping with the instrument cradle can only improve the overall process. Reverse osmosis and deionized water systems that could also alert to the need for preventive maintenance, along with water hardness indicators would provide additional quality assurance. Mandatory pre-installation requirements that address poor or hard water conditions before the washer is used to process instruments would reduce post installation investigations. This, along with scheduled preventive maintenance and QA testing would only ensure a higher-quality outcome.

More importantly, evidence-based studies to support a standard process, rather then confusing instructions from the washer, instrument, and voluntary standards writers, would better support our profession and give us teeth when we need to say no to questionable practices.

Additionally, develop an instrument disinfection technician position, with higher pay, to support specialization in an area that requires the utmost attention to insure employee and patient safety. Furthermore, develop a requirement for the number of washers and square footage necessary to support growth. The number of washers is crucial to maintaining through-put and in more cases then not should be twice the number of sterilizers. Instrument set inventories that can be increased as demands change, rather then responding to complaints and the reliance on flash sterilization.

Lastly, having the ability to upgrade your washer without replacing it every time an improvement occurs would give CS departments an ability to keep up with technology rather than watch it pass them by due to capital budget restraints. Washers, unlike sterilizers, have continued to evolve to meet the ever-challenging requirements that instrumentation pose. CS departments need to be able to keep up with change.

Tim Brooks is director of surgical services materials management/CSSPD at Yuma Regional Medical Center, and has 30 years of management experience. He hosts a Web site devoted to CSSPD and OR Materials Management at www.csspdmanager.com. He is a member of IAHCSMM.

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