\chapter{Principles of hygiene}
\begin{tabular}{l|l|l|l}
Spaulding & Body contact & Minimum decontamination & Might also need \\
classification & & requirements & \\
\hline
Non-critical & Intact skin & Cleaning & Low-level disinfectant \\
Semi-critical & Mucous membranes & Cleaning then high-level disinfectant & Sterilization \\
Critical & Sterile body cavity & Cleaning then sterilization & \\
\end{tabular}
\subsection{Cleaning}
The removal of foreign material (may not destroy infective material).l\\
May involve washing machines, ultrasound baths or manual cleaning.
\subsection{Decontamination}
Removing contaminants such that there are insufficient qualities to initiate infection.
\subsection{Disinfection}
The process of destroying all pathogenic organisms\\
Low-level disinfection kills vegetative bacteria (apart from TB and endospores), some fungi and some viruses. Common
disinfectants include chlorhexidine, 60-80\% alcohol, bleach (sodium hypochlorite), hydrogen peroxide, 2\%
gluteraldehyde and heat.
\subsection{Sterilization}
The process of destroying all forms of microbial life including bacteria, fungi viruses, spores and fungi. This may be
achieved chemically or by heat, radiation or other means.\\
\begin{itemize}
\item Dry heat - Temperatures of between $140^{\circ}C$ and $180^{\circ}C$ for up to 3 hours.
\item Autoclaving (Pressure steam sterilization) - Boiling water in a pressurized system at
temperatures of 121 or 134$^{\circ}C$ for 15 or 3 minutes is cheap and highly effective. Unsuitable for heat or
moisture sensitive equipment, powders, oils or ointments.
\item Gases. Ethylene oxide at 50-60 $^{\circ}C$ is widely used and does not damage rubber or plastics. The process
can be slow (days) and the highly explosive nature of the gas requires that de-gassing be performed post-sterilization.
\item Hydrogen peroxide plasma
\item Gamma radiation - involves exposure to gamma rays (often from a $^{60}Cobalt$ source).
\end{itemize}
Good review - see \href{http://ceaccp.oxfordjournals.org/content/4/4/103.full.pdf}{CEACCP article}\\
\vspace{1in}Concerning the sterilization of anaesthetic equipment\footnote{FTFFF}
\begin{enumerate}
\item Boiling in water for 15 min at atmospheric pressure kills bacteria and spores.
\item An autoclave pressure of 1 bar at a temperature of $120^{\circ}C$ for 15 min will kill all living organisms.
\item Gluteraldehyde 2\% has no sporicidal activity.
\item Ethylene oxide takes <1 h to be completely effective.
\item Gas plasma is a form of high-level disinfection.
\end{enumerate}
\vspace{0.5in}With regard to decontamination procedures \footnote{FFFFF}
\begin{enumerate}
\item Cleaning of equipment after use is of little importance if the item is to be autoclaved.
\item High-level disinfectants have no sporicidal activity.
\item Manual methods are much more reliable than automatic methods.
\item Chemical indicators are used in sterile packs to confirm that the contents are sterile.
\item Biological indicators are used to help distinguish processed items from unprocessed packages.
\end{enumerate}
\vspace{0.5in}Regarding the decontamination of flexible endoscopes \footnote{FTTFT}
\begin{enumerate}
\item Chlorine-releasing compounds are commonly used for disinfection
\item Endoscopes are pressure tested before disinfection
\item Ethylene oxide can be used to sterilize endoscopes
\item Low-level disinfectants are acceptable
\item They are stored vertically after use
\end{enumerate}
\vspace{0.5in}Which of the following statements is/are true \footnote{TTFFF}
\begin{enumerate}
\item An oesophageal ultrasound probe falls into Spaulding's semi-critical category
\item Semi-critical items always require high-level disinfection
\item High-level disinfectants include chlorhexidine and gluteraldehyde
\item Semi-critical items never require sterilization
\item High-level disinfection kills all bacteria and viruses
\end{enumerate}
