This video was made in 1995 by Jack van Asten, then employed by the National Institute for Public Health and the Environment (RIVM) in The Netherlands. The copyright was transferred to the European Society for Hospital Sterile Supply (ESH). Since then many copies have been distributed to sterilization professionals in Europe. A new distribution channel has been made available through the IDI website. In this way the video can be viewed by many and used as an educational tool, which will serve both the original ESH purpose and the mission of the IDI: to provide education and training. This video has a running time of approximately 22 minutes and contains four different scenes. These were recorded in a sterilizer using a fibre-optic instrument and show what happens inside the sterilizer, during a steam sterilization process.
Philip A de Vries
Former ESH Chairman (1994-1999)
The response of a Bowie & Dick type test to the dynamics of a sterilization process. Steam is a clear and therefore invisible gas, the mist you see during vacuum is a result of waterdroplets being swept away by steam and air. The retention of air in the pack caused by the condensate layer makes the pack expand during vacuum. When steam is entered the pack collapses again. During vacuum the retained air squeezes the condensate out. When steam is entered this has a similar (but smaller) effect.
A laminate pouch also responds to the dynamics of the cycle. In this case the effect is stronger because the textile in the pouch actually covers a large part of the paper side, the steam and air exchange surface. Pay special attention on the condensate ON the pouch evaporates cooling down the laminate which in turn leads to the condensation of the vapour which just evaporated from the textile.
The strong response of a basket half filled with pouches is at the least surprising. The possibility for the pouches to expand greatly influences the steam air exchange. From this scene it will be ovious that loading a sterilizer should be well evaluated and standardized to guarantee a raliable sterilization process.
Of the two metal plates only the right one is treated with instrument care liquid. One of the goals of using this liquid is to lower the surface tension of the water in order to make it run off the instrument during cleaning, facilitating drying the instruments. Any residue left (which is generally intentional) will have exactly the same effect during a sterilization cycle: the condensate will run off the instrument leaving the energy behind. As a result the left metal plate will have condensate on it, the right one will not. When vacuum is created the condensate ON the metal (left plate) is in close contact with the energy and will rapidly evaporate (the water boils on the metal). When the condensate has run off the metal there is a poor condesate-energy contact and evaporation of the condensate is relatively slow (the water boils on the edge of the metal plate). This effect may cause wet loads.