title: Is Transducer Hygiene sufficient when Vaginal Probes are used in the Clinical Routine?
abstract: Vaginal ultrasound probes are semi-critical Group A medical products which must be disinfected following the manufacturer's instructions after every patient examination. According to the "Essential Requirements for Medical Devices (Directive 93/42/EEC, Annex I, paragraph 13)" the manufacturer's instructions for use for reusable products must contain suitable instructions for preparation processes. This presumes both an effective and material-compatible method. Evidence of effectiveness must be validated.In the Editorial in issue 1 Ultraschall in der Medizin/European Journal of Ultrasound 2005 we discussed the topic of transducer hygiene and stated that proper handling and cleaning as well as disinfection of probes in daily use are indispensable. This applies particularly to vaginal ultrasound probes routinely used in gynecological and obstetrical clinics, gynecological practices as well as IVF centers Normally the probe used in a transvaginal ultrasound examination is covered with a latex protective cover (with CE marking) which contains a certain amount of ultrasound gel. After the examination, the cover is removed and disposed of, and the gel is removed from the transducer. Since handling of the probe, ultrasound gel and cover can result in smear infections and cross-contamination with various pathogens (e. g. MRSA, HBV, HCV, HIV, herpes papilloma and cytomegalic viruses), after the protective cover is removed, the probe must be cleaned and subjected to disinfection with a bactericidal, fungicidal and virucidal effect. This is especially important in the event the cover ruptures during the vaginal examination, and the probe comes into direct contact with vaginal secretions or blood. The same likewise applies if the sterile protective cover is perforated during a follicular puncture. Usually special bactericidal, levurocidal and virucidal wipes or special submersion disinfection methods are available for disinfecting the vaginal ultrasound probes 11. Using special virucidal wipes on the probes is considered low-level disinfection. Primarily quaternary ammonia compounds are employed for this procedure. This method is easily applicable, has good cleaning characteristics, is effective against HPV and has high skin tolerance. However, it has the disadvantage of not removing all microorganisms during the disinfection process. Immersion procedures are high-level disinfection methods during which the transducer head is dipped in a special fluid for a certain amount of time. The disinfectants used for this include e. g. preparations based on glutaraldehyde or succinic aldehyde. However, in practice immersion disinfection has a number of disadvantages 13: 1. The procedure cannot be validated. 2. The probe permanently attached to the device must be placed in a separate holder and disinfected for at least 15 minutes. This is impracticable in routine operations in a clinic, outpatient facility or practice with a high number of examinations. 3. After this disinfection method, the probe has to be thoroughly rinsed with potable or higher-quality water in order to remove remnants of allergenic or locally toxic substances. 4. Frequently examinations take place in small interior areas with poor ventilation, thus under some circumstances posing an inhalant-related health hazard. 5. The required virucidal effect is frequently not achieved within 15 minutes 13. Furthermore, extended probe contact with liquid disinfecting agents in the long run results in increased wear of the transducer head membrane.Therefore it was interesting to note that in 2009 a fully-automatic disinfection system for ultrasound probes was introduced to the market (Trophon(EPR). This product, developed in Australia, promised relatively rapid high-level disinfection (HLD). During this software-controlled, mechanical disinfection procedure, the entire ultrasound probe (transducer head and handle) is placed in a sealed disinfection chamber, then hydrogen peroxide (H2O2) is discharged as an anti-microbial aerosol into the closed chamber.  The ultra-fine mist wets the entire surface of the probe with H2O2, thereby achieving high-level disinfection of the entire ultrasound probe. At the end of the process, a catalytic decomposition system breaks down the H2O2 into environmentally-friendly oxygen and water. When the chamber is opened, the probe is dry and ready for immediate use. The fully-automatic device was designed as a table unit to be placed directly next to the ultrasound equipment so that the probe does not need to be disconnected from the base unit. The entire disinfection process lasts 7 minutes: 2 minutes for the application and 5 minutes to remove the aerosol residue. In a validation study using carrier tests, Heeg and Gauer in 2014 showed that this procedure genuinely achieved HLD of ultrasound probes within 7 minutes, thus making it suitable for daily clinical routine. The procedure fulfills all requirements for HLD based on the medical device classification according to the legally-prescribed recommendation of the Commission for Hospital Hygiene and Prevention of Infection and the Federal Institute for Drugs and Medical Products (KRINKO/BfArM) in Germany. In the USA, this method was approved by the FDA as well as the leading probe manufacturers, and bears the testing certificate of the German Society for Hospital Hygiene (DGKH).All in all, it should be stated that the sole use of a latex protective cover when using a vaginal probe does not meet the necessary standard of care required for the provision of semi-critical medical products according to the joint recommendation of the German Federal Institute for Drugs and Medical Products (BfArM) and Commission for Hospital Hygiene and Prevention of Infection of the Robert Koch Institute, and constitutes a contravention of necessary patient and user protections. Use of the protective cover does not rule out smear infections and cross-contamination; therefore after each examination, the probe, after removal of the cover, must undergo disinfection measures providing bactericidal, fungicidal and virucidal effects. Since the transducer handle also poses a significant risk of transmission of germs, this component must likewise be sufficiently disinfected. In the event of perforation or rupture of the latex cover, thus resulting in the probe coming into contact with vaginal secretions or blood, the probe must be not only cleaned, but effectively disinfected with a virucide as well. It should also be noted that infection by bacteria and viruses can be caused not only by a contaminated probe, but by the ultrasound gel as well. According to studies by Heeg and Gauer 15, Buescher et al. as well as Ryndock et al., the fully automatic HLD system operated with hydrogen peroxide is currently the only validated system proven to provide HLD of ultrasound probes in a 7-minute cycle, thus suitable for application in the daily routine. Likewise it can also be presumed that this procedure also offers good material compatibility.
authors.forename: E
authors.initials: E
authors.lastname: Merz
mesh_terms: D004203:Disinfection / Q000295:instrumentation* / Q000592:standards*; D019160:Endosonography / Q000295:instrumentation* / Q000592:standards*; D004867:Equipment Design; D017743:Equipment Reuse / Q000592:standards*; D005260:Female; D006801:Humans; D014159:Transducers / Q000592:standards*; D016216:Ultrasonography, Prenatal / Q000295:instrumentation* / Q000592:standards*; D014621:Vagina / Q000000981:diagnostic imaging*