The goal of this prospective controlled trial was to assess the efficacy of sterile disposable sheath usage to prevent cross-contamination during endoscopic procedures with a fi beroptic nasopharyngolaryngoscope (FNPL), as compared to immersion of the instrument in a germicidal liquid. Many otolaryngologists who use FNPLs to evaluate patients use a liquid germicide for disinfection; this requires multiple steps, including preparation, cleansing, immersion for specified length of time, and drying. In order for this disinfection method to be highly effective, clinical staff must strictly adhere to protocols. Elackattu et al note that not all medical assistants have extensive experience performing this disinfection procedure, and some may object to exposure to potentially toxic chemicals during the immersion process. As an alternative, disposable sterile sheaths were developed to fi t over the FNPL and are marketed as a means of preventing cross-contamination between patients. The investigators in this study evaluated microbial presence on endoscopes after use with a sterile sheath, and comparatively analyzed microbes cultured from endoscopes that were used in a procedure without a sheath, and were then disinfected with a liquid germicide. Patients were examined in an otolaryngology clinic and assigned to one of two groups: the liquid germicidal disinfection group, and the sterile sheath group. The endoscopes used in the sterile sheath procedures were cleaned between patients as per manufacturer recommendations; immersion in enzymatic detergent after sheath removal, friction rub with water rinse, intermediate level disinfection with 70% alcohol-soaked gauze, and air dry. The endoscopes in the liquid germicide group went through high-level disinfection as a required additional step beyond intermediate-level disinfection.
Culture samples were collected prior to use on the patient and after high-level disinfection on the immersion group of endoscopes; for the sterile sheath group, samples were taken three times: prior to use on the patient, after sheath removal, and after intermediate level disinfection.
The results of the microbial study revealed that the sterile sheath system is as effective as using a liquid germicidal system for preventing cross-contamination when using FNPL’s sequentially in a series of patients. The investigators noted that baseline contamination can be a concern: in this study, about 8% of the insertion tubes in either group and a small percentage of control handles in either group had organisms on them at baseline, after having undergone high-level disinfection (a requirement of the study design). This may have been the result of improper storage or other contamination during transport. Overall, the results of the study suggest that using an individually-packaged disposable sterile sheath on an FNPL does prevent microbes from adhering to the insertion tube of the scope, thus providing a method to avoid the transmission of infection from one patient to another.
The authors commented that while the immersion method is known to be effective for disinfecting endoscopes, it is not a perfect method, in that a sterilization process is required to destroy all living micro-organisms (bacterial spores and viruses) which may still be present after high level disinfection. The article also discusses the many adverse reactions which have been reported by clinical staff (e.g., asthma, skin disorders) after exposure to noxious liquid germicides; and points out that other methods of disinfection which involve dry heat, steam, hydrogen peroxide, or peracetic acid have not been widely adopted for a variety of reasons.
In their conclusion, Elackattu et al mentioned the issue of patient perception as a significant consideration. They found that typical patients derive a sense of security about sterility when they see a sterile sheath being removed from its one-time-use packaging and placed over the endoscope immediately prior to insertion of the scope into his/her nose.