Reprocessing Flexible and Rigid Laryngoscopes:
Are Quaternary Ammonium Disinfectants Adequate?
By Lawrence F. Muscarella, PhD
Laryngoscopes are one of several different types of rigid and flexible endoscopes sometimes referred to as ENT (or ear-nose-throat) endoscopes. Examples of flexible laryngoscopes include rhinolaryngoscopes and nasopharyngo-laryngoscopes. Rhino-laryngoscopes use fiber-optic or video technology to examine, diagnose and evaluate the normal physiologic and pathologic conditions of, among other organs, the larynx. Most models are used for diagnostic procedures and do not have any internal channels. Some models, however, feature a single working channel, a suction control valve, and a biopsy inlet port that can be used for aspiration, removal of foreign objects, and performing biopsies. Naso-pharyngo-laryngoscopes are similar in design and function to rhino-laryngoscopes. Rigid laryngoscopes, on the other hand, are used to expose and view the larynx to facilitate endotracheal intubation. These endoscopes feature a fiber-optic disposable or reusable blade that is available in different sizes, may be curved or straight and connects to the laryngoscopes handle.
Classification of Medical Instruments
Before it can be determined whether selection of a quaternary ammonium product is appropriate for cleaning and disinfecting rigid and flexible laryngoscopes, it is first necessary to evaluate the risk of nosocomial infection associated with the use of these instruments. Application of a widely accepted three-tiered classification scheme for medical instruments aids in the evaluation of this risk. According to this scheme, medical instruments that penetrate sterile tissue, enter the vasculature, or contact the patients blood are classified as critical instruments, because the risk of nosocomial infection associated with their use is high.1-4 (See Table 1.)
Semi-critical instruments, on the other hand, contact mucous membranes or non-intact skin, but do not typically penetrate sterile tissue (see Table 1). The risk of nosocomial infection associated with instruments in this second category, while still potentially significant, is markedly less than the risk associated with critical instruments. Rhinolaryngoscopes, naso-pharyngo-laryngoscopes, and the blades and handles of rigid laryngoscopes are classified in this second category.1-4 Medical instruments that either do not directly contact the patient or only contact a patients intact skin pose a low risk of nosocomial infection and therefore are classified as non-critical instruments (see Table 1).1,2 Most environmental surfaces, including walls, floors and sink tops, are included in this third and low-risk category.
Sterilization and the Three Levels of Disinfection
Once the risk of nosocomial infection associated with the use of rigid and flexible laryngoscopes has been evaluated and their classification as semi-critical instruments understood, a review of: published endoscope reprocessing and infection control guidelines; the definitions of sterilization and disinfection; and the labels of quaternary ammonium products is necessary to determine whether they are sufficiently effective to satisfy the minimum reprocessing standards required to prevent rigid and flexible laryngoscopes (and other semi-critical instruments) from transmitting disease.
Whereas sterilization is an absolute term and refers to a process that destroys all types of microorganisms including high numbers of resistant bacterial endospores, disinfection is a relative term and refers to different types of processes that vary in effectiveness. As displayed in Table 2 in decreasing order of biocidal effectiveness, disinfection processes can be classified into one of three categories, or levels: high-level disinfection (HLD), intermediate-level disinfection (ILD), and low-level disinfection (LLD).1-4 Each of these three levels of disinfection is, in effect, defined and differentiated from one another by specific indicator microorganisms that each respective level can and cannot reliably destroy. The relative resistance of microorganisms to sterilization and the three levels of disinfection is displayed in Table 3.1. The more resistant the microorganism, the higher the level of disinfection (or sterilization) required to destroy it.
Defined as the highest and most effective level of disinfection, HLD destroys mycobacteria (i.e., is tuberculocidal), viruses, fungal spores and vegetative bacteria.1 HLD also destroys some, but not all, bacterial endospores. It is the limited sporicidal activity of HLD that distinguishes it from sterilization (which destroys all microorganisms, including high numbers of bacterial endospores) and the other two levels of disinfection (neither of which is sporicidal) (see Tables 2 and 3). Most importantly, HLD destroys all pathogenic microorganisms encountered in the endoscopic setting, including Clostridium difficile, a spore-forming bacterium. (Almost all spore-forming bacteria are non-pathogenic. Those few that do produce disease such as Bacillus anthracis and some species of the Clostridium genuseither are destroyed by HLD or have not been associated with infection following endoscopy.5
It is for this reason that differences in the infection rates of rigid and flexible endoscopes subjected to sterilization or HLD have not been documented.5 Liquid chemical sterilants (LCSs) are frequently used to achieve HLD of endoscopes (see Table 2). LCSs that achieve HLD during short immersion times typically are sporicidal and destroy high numbers of bacterial endospores during long exposure times. One level below HLD is a less effective process known as ILD (see Table 2).1 Whereas processes that achieve sterilization and HLD are regulated by the Food and Drug Administration (FDA), ILDs (and LLDs) are regulated instead by the Environmental Protection Agency (EPA). In general, ILD destroys lipid or medium-sized viruses, most non-lipid or small viruses, fungal spores, and vegetative bacteria. Like HLD, ILD is tuberculocidal. But what differentiates ILD from HLD (and sterilization) is its inability to destroy bacterial endospores, even during long exposure times. Examples of ILDs include iodophor and phenolic compounds. Concentrated quaternary ammonium cleaner/disinfectants may also be classified as ILDs. The third and lowest level of disinfection, LLD, destroys fungal spores, vegetative bacteria, and lipid or medium-sized viruses.1 But unlike ILD, LLD is not tuberculocidal (see Tables 2 and 3). Examples include diluted quaternary ammonium cleaner/disinfectants.
Selection of a Sterilization, Disinfection Process
For many reasons, selection of an appropriate sterilization or disinfection process or technology for reprocessing a specific reusable medical instrument (or environmental surface in the healthcare setting) is not always straightforward. If every reusable medical instrument were constructed of stainless steel and other durable materials not damaged by heat, pressure and moisture, few reprocessing dilemmas would arise, and the simple and obvious, if only, choice for reprocessing instruments would be steam sterilization. Indeed, steam sterilization is the method of choice, because it is effective, fast acting, and inexpensive.6
But the demand to improve patient morbidity, minimize the invasiveness of surgery, and reduce healthcare costs, coupled with significant advances in fiber-optic technology and materials engineering, spurned the development of delicate instruments many of which are heat-sensitive and arguably designed more to simplify complicated medical procedures than to facilitate reprocessing. For these heat-sensitive instruments, several different types of low-temperature sterilization and disinfection processes were developed.
In addition to raising questions of materials compatibility, however, some low-temperature sterilization processes may be less effective and considerably more expensive per cycle than steam sterilization.6 Moreover, complicating selection of an appropriate reprocessing process for a specific heat-sensitive reusable instrument, some low-temperature sterilization processes have limited applications and are contraindicated for reprocessing instruments with long and narrow internal channels, such as flexible gastrointestinal endoscopes. Also, not every reusable instrument requires sterilization. In many instances, disinfection is adequate to prevent patient-to-patient disease transmission.
Although at times challenging, selection of an appropriate reprocessing technology for a specific instrument can be simplified by dovetailing the three-tiered classification scheme for medical instruments displayed in Table 1 with the definitions and relative effectiveness of sterilization and disinfection (see Tables 2 and 3). In general, critical instruments, such as reusable biopsy forceps, require steam sterilization (Table 2).1,7,8 For heatsensitive critical instruments, such as some models of arthroscopes and laparoscopes, a low-temperature sterilization process may be indicated.1 (Refer to the sterilizers labeling and the instruments reprocessing instructions regarding recommended processes, effectiveness and compatibility.) Alternatively, if sterilization is not feasible, HLD is recommended.1
HLD is also recommended for semi-critical instruments (although a low-temperature sterilization process may also be acceptable, as well as steam sterilization if the instrument is not damaged by heat).1,7,8 Published guidelines emphasize that subjecting an arthroscope, laparoscope (critical instruments) or a flexible endoscope (a semi-critical instrument) to HLD instead of sterilization is acceptable and does not pose an infection risk.1,5,7,8 In accordance with published guidelines, their classification as semi-critical instruments (see Table 1), and their manufacturers reprocessing instructions, HLD is recommended for rhino-laryngoscopes, naso-pharyngo-laryngoscopes, and the blades and handles of rigid laryngoscopes (see Table 1).1-12
Finally, products that achieve ILD and LLD specifically, general purpose cleaner/disinfectants approved for use in medical facilities (see Table 2) are recommended for and limited to cleaning and disinfecting non-critical instruments and environmental surfaces.1 (With very few exceptions, ILD may be acceptable for a limited number of semi-critical devices, such as hydrotherapy tanks, but not endoscopes. Refer to the specific instruments reprocessing instructions.)
Quaternary Ammonium Products
Quaternary ammonium products (or compounds) are broad-spectrum, EPA-registered, cleaner/disinfectants. Depending on their concentrations, quaternary ammonium products intended for use in medical facilities are labeled for ILD or LLD and therefore may be used to clean, deodorize and disinfect non-critical items and hard, non-porous environmental surfaces. In accordance with their labeling, quaternary ammonium products may also be used to pre-clean critical and semi-critical medical instruments prior to HLD or (sterilization). (Refer to the instruments reprocessing instructions to ensure materials compatibility with quaternary ammonium cleaner/disinfectants.)
Quaternary ammonium cleaner/disinfectants used in medical facilities are labeled for ILD or LLD not HLD and therefore, while indicated for cleaning and disinfecting non-critical items and environmental surfaces, are contraindicated for flexible endoscopes. In particular, use of a quaternary ammonium disinfectant to clean and disinfect rhino-laryngoscopes, nasopharyngo- laryngoscopes, other types of flexible laryngoscopes, and the blades and handles of rigid laryngoscopes is not an accepted practice, potentially unsafe, and a violation of the standard of care. Cleaning using an appropriate detergent (e.g., enzymatic detergent) followed by HLD at a minimum is required for these semi-critical instruments as part of a complete and validated reprocessing protocol.1-4,10-12 Use of quaternary ammonium products to clean and disinfect surgical instruments has been linked to disease transmission.9
Further, although the handles of rigid laryngoscopes may not always directly contact the patient, reports have demonstrated their contamination with opportunistic pathogens.10 Published guidelines recommend that these handles (and blades) be cleaned and subjected to HLD (or sterilization)1-4,10,12. Steam sterilization of the laryngoscopes handle and blade may also be acceptable, although flash sterilization may be contraindicated. Review the laryngoscopes reprocessing instructions for a list of compatible processes.
Lawrence F Muscarella, PhD, is the director of research and development and chief, infection control for Custom Ultrasonics, Inc. He is also editor of The Q-Net Monthly (www.myendosite.com). He can be reached via email at [email protected].
Table 1: Classification Scheme for Medical Instruments
Penetrate sterile tissue, enter the vasculature, or contact the patients blood.
Examples: Cardiac catheters, biopsy forceps and implants.
Contact mucous membranes or non-intact skin.
Examples: Rhino-laryngoscopes, naso-pharyngo-laryngoscopes, and the blades and handles of rigid laryngoscopes.1-4
Do not directly contact the patient, or only contact the patients intact skin.
Examples: Blood pressure cuffs, stethoscopes and bedpans; and environmental surfaces, such as walls, floors and sink tops.
Table 2: The Definitions, Characteristics and Relative Effectiveness of Sterilization and Disinfection
(Sterilization or the level of disinfection appropriate for critical, semicritical and non-critical medical instruments is listed)
Sterilization Destroys all microorganisms, including bacterial
Sporicidal, tuberculocidal, virucidal, fungicidal and bactericidal.
Uses bacterial endospores as biological indicators.
Examples: Pressurized steam,
ethylene oxide gas, hydrogen peroxide plasma.
Primarily used for critical instruments.
High-level disinfection (HLD)
Destroys all pathogenic microorganisms, including some bacterial endospores during short exposure times.
Typically destroys high numbers of bacterial endospores during long exposures times.
Sporicidal (limited), tuberculocidal, virucidal, fungicidal and bactericidal.
Uses mycobacteria as indicators of effectiveness.
Examples: 2 percent glutaraldehyde,
7.5 percent hydrogen peroxide, 0.2 percent peracetic acid.
Primarily used for semicritical instruments.
Intermediate-level disinfection (ILD)
Destroys many types of microorganisms including mycobacteria.
Tuberculocidal, virucidal, fungicidal and bactericidal.
May use mycobacteria, viruses as indicators of effectiveness.
Examples: 70 percent isopropyl alcohol, iodophor and phenolic compounds, concentrated quaternary ammonium compounds (e.g., hospital cleaner/disinfectants with a tuberculocidal claim). Primarily used for non-critical instruments.
Low-level disinfection (LLD)
Destroys some types of microorganisms.
Neither sporicidal nor tuberculocidal.
Virucidal (limited), fungicidal and bactericidal.
May use the hepatitis B virus, HIV as indicators of effectiveness.
Examples: Diluted quaternary
ammonium compounds (e.g., hospital cleaner/disinfectants without a
Primarily used for non-critical instruments.
Table 3: The Relative Resistance of Different Types of
Microorganisms to Sterilization and Disinfection
(Listed in decreasing order of resistance of microorganisms to sterilization and disinfection. In general, bacterial endospores and prions are the hardest to destroy and lipid viruses are the easiest to destroy.)
Prions May require extended, multiple sterilization
May be responsible for transmissible spongiform encephalopathies.
Bacterial endospores Destroyed
Some bacterial endospores can also be destroyed by HLD.*
Example: Bacillus stearothermophilus
Mycobacteria Destroyed by sterilization, HLD and ILD.
Example: Mycobacterium tuberculosis
or small viruses
Destroyed by sterilization, HLD and ILD.
Example: the polio virus
(molds and yeasts)
Destroyed by sterilization, HLD and ILD.
Some fungi are also destroyed by LLD.
Example: Candida albicans
Destroyed by sterilization, HLD, ILD and LLD.
Example: Pseudomonas aeruginosa
or medium-sized viruses
Destroyed by sterilization, HLD, ILD and LLD.
Example: the hepatitis B virus, HIV *HLD = High-level disinfection; ILD = Intermediate-level disinfection; LLD = Low-level disinfection
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