Endoscope Washer-Disinfector


BSG working party report 2003 argues that decontamination of endoscope should be done at the start and end of every list, and between subjects, by competent personnel in special rooms. Also water for endoscope reprocessors should be particle and microorganism- free (British Society of Gastroenterology Endoscfopy Committee 2003). Further, the report recommends weekly assessment of microbiological content.


Apparently, this is the latest technique for removing accumulated debris from the device thereby circumventing the hand cleaning stage of the decontamination procedure. Numerous water jets and the increased alkalinity of the detergent enable thorough cleaning of heavily soiled apparatus (Richards et al 2001). Neutralizing rinse proceeds the primary cleaning to restore the pH of the instrument to neutral. Minimal agitation of water prevents damage by tossing of delicate instruments such as the endoscope against the walls of the wash tray. Washer-Disinfector eliminates the hand cleaning process, and can substitute the ultrasonic washer (Rey et al 2005).

Water quality

It known that value depreciation of medical apparatus is a product of the quality of water used in its processing. Undesirable water components can impinge on the appearance and treatment practice of the apparatus and materials. For instance due to water hardness, mineral deposition can occur on the surfaces and may subsequently corrode the instrument (Instrument Preparation Working Group 2009, p. 17).

According to the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) (2010, p. 16), standard washer disinfectors are not designed to comply with the design characteristics of multifaceted medical instruments like the narrow lumen common with the single user devices (SUDs). Nevertheless, after cleaning using a washer-disinfector, the apparatus are disinfected to get rid of impending microorganism, which may cause contamination. Disinfection process can either be thermal or chemical depending on the characteristics of the surface of the device.

Generally, thermal stable materials are disinfected using water at 80 to 900C for less than 10 min. This method kills parasites, viruses, microscopic fungi, and the vegetative forms of bacteria. On the other hand, for thermo liable materials like in the case of flexible endoscopes, disinfection is done by an aqueous chemical disinfectant at comparatively low temperatures between 25-600C, prior to rinsing with a high microbiological quality water (Scientific Committee on Emerging and Newly Identified Health Risks 2010, p. 16).

Richards et al (2001 p.2) argues that mains and tap water are unsterile and can lead to recontamination of endoscope thereby transmitting infection to patients who undergo endoscopy. Therefore the water for cleaning and disinfecting the endoscope should meet some predetermined standards. He further asserts that preparation of rinse water of desirable bacterial count remains a challenge which evades the recognition of the general medical fraternity.

Measuring water purity

Water quality (Purite Limited n. d.) refers to the ability of the ionic water components to conduct electricity. Besides conductivity as measure of salt concentrations, specific constituents such as heavy metals and hardness can be determined. Moreover, the microbial excellence of water is crucial because use of medical instruments can be invasive and can increase the risk for contamination or adverse effect. Usually the microbiological quality is determined by measuring the total viable count (tvc), colony forming units (cfu) or endotoxin concentration.

Softened water

Softening of water prevents formation of deposits during steam generation stage of endoscope decontamination. Also the steam residue (a measure of water quality) is increased because the heavier calcium ion is substituted with two sodium ions. Most importantly, softened water has an increase pH form the range of 7.2-7.4 to 7.4-8.0. The alkalinity of sodium bicarbonate generated in softening is higher than of magnesium or calcium bicarbonate. Alkalinity of the softened water is further increased by heating and the space of time of disinfection. The increase in alkalinity hinders rinsing of alkaline cleaning material following the cleaning rinse phase (Michels 2005).

Final rinsing

There are two basic criteria of final rinsing of endoscope washer- disinfector, they are

  • always dispose of the rinse water following every use to avoid accumulation of the disinfectant and subsequent damage to mucous membrane,
  • avoid using one container for the initial and final rinsing.

This process is usually done under running filtered boiled water. This is done by immersing the endoscope in drinking-quality water to irrigate every conduit (Rey et al 2005, p. 6, 7). In case the water for rinsing is hard, it should be softened. Water for final rinse should be screened for microorganism at least on weekly basis (Rey et al 2005, p. 18).

According to Mitchell et al (2007, p. 21), distilled or de-ionized water ought to be used for final rinsing of the apparatus after the apparent sterilization process. This water has a pH range between pH 6.7 to 7.2 and neutralizes a surface pH by rinsing off alkaline wash water. Additionally, distilled water is free from dissolved and undissolved particles which cling on the surface of the apparatus.

Comparison and contrast between water for steam generation and endoclave washer-disinfector

According to Purite Limited (n. d.), water for steam generation or for final rinse phase should be pure since it is the last water used on the surfaces of the medical devices after sterilization. The bacterial and endotoxin level of the water is extremely low, and pipes for conveying this water ought to meet the proper standards.

Additionally, the mineral proportion of the water is low to prevent staining or concealment of the microorganism. Pure water availability for steam generation and final rinse is ensured through incorporation of water softeners, bacterial and carbons filters, and reverse osmosis.

Purified water is used for the final rinse stage for computerized washer-disinfectors. It should be put in consideration that the water used in this phase does not re-contaminate the endoscope or leave salt deposits which may support potentially infectious microorganism or their toxins. Contrary, the water used for autoclave is raised as steam to facilitate sterilisation of endoscope. Nevertheless, this last phase should not lead to recontamination of the device just like the washer disinfector stage (Bradley, C. R. & Babb 1995, p. 540).

Water for the final rinse phase of endoscope washer-disinfector must be pathogen free. Humphrey and Lee (1999, p.76) argues that the water for GIT endoscopes should necessarily not be sterile. However, numerous endoscopy departments perform diverse processes which allow endoscopes to be cleansed or disinfected using one washer-disinfector.

Reference List

Bradley, C. R. & Babb, J. R., 1995. Endoscope decontamination: automated vs. manual. J Hosp Infect, Vol. 30, pp. 537–542.

British society of gastroenterology endoscfopy committee., 2003. BSG guidelines for decontamination of equipment for gastroenterology endoscopy. BSG working party report.

Humphreys, H & Lee, J V., 1999 Water quality for endoscopy washer-disinfectors. Journal of Hospital Infection, Vol. 42, pp. 76-78.

Instrument preparation working group., 2009. Proper maintenance of instruments. Proper Maintenance of Instruments, 9th ed. Web.

Mitchell, D. H, Hicks, L. J, Chiew, R, Mantanaro, J. C., & Chen, S. C., 2007. Pseudoepidemic of Legionella pneumophila serogroup 6 associated with contaminated bronchoscopes. J Hosp Infect, Vol. 37, pp. 19–23.

Michels, W., 2005. Washing with any water: water softening,properties and effects in machine preparation. Journal for hygiene in hospitals and medical practice. Purite Limited, Purite in healthcare: water purification for decontamination processes, Oxon; UK.

Rey, J F, Bjorkman D, Duforest-Rey D, Axon A, Saenz R, Fried M, et al., 2005. WGO-OMGE and OMED Practice guidelines: Endoscope disinfection.

Richards J , Spencer, R, Fraise A, Lee J et al., 2001. Rinse water for heat labile endoscopy equipment, A report from a joint working group of the hospital infection society and the public laboratory services. Bowthorpe Road, Norwich.

Scientific Committee on Emerging and Newly Identified Health Risks., 2010. The safety of reprocessed medical devices marketed for single-use. European Commission: Brussels. Web.