INFECTION PREVENTION & CONTROL


Cleaning instruments outside Spray arms distribute water jets inside the chamber. Their primary function is to direct water pressure onto the instruments, as well as cleaning chamber walls. That is the first main problem. Spray arms rotate around the centre of rotation and, if looked from above the round area located directly underneath, the spray arm does not cover the entire shelf of the instrument carrier that is typically square or rectangular. In the worst-case scenario of rectangular shelves, the area outside the direct coverage of the spray arms is sometimes nearly as big as one directly underneath the spray arm.


The only way to clean instruments located in the corners of the shelf is to design the spray arms such that jets of water at the end of the spray arm come out at an extreme angle. That is why the characteristics of cleaning performance right underneath the spray arm and outside its “perimeter” are different, and this is why cleaning performance on the entire shelf is not uniform. Because of the construction of the spray arm, the area right underneath the centre of rotation is also sometimes problematic, simply because it is difficult to direct the jets to cover that area effectively – again, creating a region of different cleaning performance. Taking the above characteristics into consideration, it is critical to evaluate cleaning performance in those areas and understand the nature and degree of performance differences. Since the washer disinfector does not see contamination, the worst-case scenario location needs to be identified to ensure the cleaning quality of the entire load can pass the cleanliness criteria.


Every time a new set of instruments is loaded to the washer, we create a unique challenge for the washer. Instruments and instrument baskets become a part of the complex system of cleaning mechanics.


Cleaning the inside of instruments


The mechanics of internal cleaning of instruments with hollow channels are governed by the water that flows through


them. The flow, in this case, is what delivers mechanical energy and chemicals. When it comes to the effectiveness, the matter is quite complex since, when it comes to narrow lumen cleaning, the turbulent character of the flow is desired to improve the contamination removal from the walls. The character of the flow depends on the velocity of the fluid in the channel, and it can be instinctively concluded that the higher the velocity, the more turbulent the flow becomes. There is also a higher mechanical force applied to the debris stuck to the channel walls. In a given hollow channel, that speed will directly depend on the pressure produced by the flushing system. At a first glance, it is a fairly simple setup. A pump delivers pressure to the instrument rack and through various connectors or accessories further into the instruments. Problems start when the pressure losses from all the connections and multiple instruments are put together. Every pump has its “flow versus pressure” characteristic. In essence, the higher the flow the lower the pressure, and vice versa. This means that the more instruments get connected (each requiring a volume of fluid to go through it) the lower the overall system pressure… and the lower the pressure, the lower the velocity of the fluid in each lumen. To make matters worse, not all instruments have dedicated flushing ports with dedicated connectors that make certain no leaks and


46 I WWW.CLINICALSERVICESJOURNAL.COM SEPTEMBER 2019


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