In emergency medical services, hygiene measures take place in the area of conflict between well-planned routine transports and acute emergency measures under time pressure and in a changing environment. Preclinical information about the presence of transmissible diseases or pathogens is not reliably available in emergency operations, which means that consistent compliance with basic hygiene measures is generally required in all operations. This means that hygiene measures in emergency services must be primarily effective, appropriate, practicable and economical. For this reason, hygienic standards must be demanded that minimize the risk of nosocomial infections of the patient as well as the transmission of pathogens to the emergency personnel (Treffer, Hossfeld, Helm Weißleder, 2018; Finsterer, Kraus, Birkholz, 2021). Increased popularity was gained by fogging devices for disinfection in the context of the COVID-19 pandemic, although the procedure appeared unacceptable in routine rescue service due to a fogging time of 30 to 90 minutes. Similarly, it could be stated that fundamental prerequisites for handling highly infectious patients are not material resources alone, but in particular the safe mastery of the required procedures (Finsterer, Kraus, Birkholz, 2021; Pfaff, 2022). Karl et al. (2022) were able to show a discrepancy between the 10 most frequently touched surfaces in the ambulance and the 10 most frequently disinfected surfaces. As a result, following Vikke es al. (2015), the potential danger of smear disinfection for ambulance personnel and subsequently patients to be transported as well as the possibility of germ reduction in periods without disinfection, e.g., by antimicrobial coatings, were discussed (Karl, Huefner, Pemmerl, 2021).
PLASMOCAR® uses the physical cold plasma technology (Fricke, Koban et al., 2012; Hoffmann, Berganza et al., 2013; Lerouge, Wertheimer et al., 2001; Harder 2021). Only ambient air and electricity are required to produce the cold plasma. Specifically, oxidative reaction products are generated from atmospheric oxygen and water vapor, which eliminate microorganisms and preserve human cells (Liang, Wu et al. 2012; Bailey, Pemmaraju et al. 2014; Daeschlein, Scholz et al. 2012). The cell membrane of the microorganisms is perforated by the charged particles of the cold plasma (Daeschlein, Napp et al. 2014).
The use of the PLASMOCAR® can be described as harmless from three different perspectives:
1. Medical safety
PLASMOCAR® can eliminate microorganisms and preserve human cells (Fig. 2). Reason for this is the physical process, which requires only ambient air and electricity to produce the cold plasma. The cell membrane of the microorganisms is perforated by the charged particles of the cold plasma. This is impossible in human cells because proteins in the form of enzymes break down the cold plasma and protect the cells (Fricke, Tresp et al. 2012; Boxhammer, Li et. al. 2013).
The medical justification can be supported by toxicity tests. For instance, an Ames (EN ISO 10993-3) and a Cytotox test (EN ISO 10993-5) were performed for the cold plasma process on which PLASMOCAR® is based. In both tests, no mutagenic effect was found in human cells.
2. Toxicological safety
The medical justification can be supported by toxicity tests. For instance, an Ames (EN ISO 10993-3) and a Cytotox test (EN ISO 10993-5) were performed for the cold plasma process on which PLASMOCAR® is based. In both tests, no mutagenic effect was found in human cells.
3. Legal safety
PLASMOCAR® is based on a purely physical process (Ehlbeck, Schnabel et al. 2011; Hoffmann, Berganza et al. 2013). Against this background, the Low Voltage Directive for electrical equipment applies. The Low Voltage Directive specifies emission limits such as the emission of the substance ozone (IEC 60335-2-65). This directive is supported by a recommendation of the VDI (Association of German Engineers). The expert recommendation from VDI-EE 4300 Sheet 14 states that air purification devices may emit a maximum residual ozone concentration of 10 µg/m³.
The assessment of the company CeCert dated 21.12.2021 as well as the assessment of the TÜV NORD Umweltschutz GmbH & Co. KG) dated 22.06.2022 confirm compliance with the limit values.
"Disinfection" describes a microbiocidal process whose aim is to reduce an initial germ load to such an extent that there is no longer any risk of infection from the remaining, residual microorganisms. This distinguishes disinfection from sterilization, whose goal is "absolute sterility" (with a statistical certainty of 1:1,000,000 for a non-sterile product --> SAL = sterility assurance level). The germ reduction performance is expressed in log levels, which as an exponent to the base 10 describe by how many times the germ reduction has occurred (Mazzola, Penna et al. 2003, Kahrs 1995).
Log reduction factors of 3 to 5 are recommended for disinfection processes, whereby a log reduction factor of > 3 should be present for surface disinfection, which means a germ count reduction of at least 10− 3 times, which corresponds to a reduction of 1:1,000 = 1 germ in 1000 germs is still viable after application of the measure. The aim of disinfection is thus the elimination of infectivity, i.e. the state of "asepsis" is aimed for (Mazzola, Penna et al. 2003). Commercially available surface disinfectants generally meet these requirements in full. However, correct application is a prerequisite, i.e. the effective concentration in the local environment, exposure time and, if necessary, mechanical manipulation of the surfaces to be disinfected must be correctly mapped in accordance with the manufacturer's instructions under which the product was validated. This is where the "human bias" comes into play, i.e. the success of the application depends to a large extent on the way in which it is used. Different people use surface disinfectants in different ways, and there is also the general problem of personnel and time constraints, especially in the area of acute care (emergency services and general patient transport) (Nobile, Pasquarella et a. 2018).
Furthermore, the use of wipes containing active ingredients, which has been propagated since the 2000s, poses a problem from the point of view of hygiene. The active ingredients, which are usually alcoholic or cationic surfactant-based, are only effective where application and wetting take place. Because of possible "overspray," the previously well-established spray disinfectants are no longer recommended (Below, Partecke et al. 2012). This results in the problem of wetting gaps, since only the generally accessible surfaces are reached by application of the wipes. The wiping process does not reach certain, edges, beads, handles, blind holes, and folds. As a result, it is not possible to disinfect all functional surfaces in a reasonable time of approximately 30 minutes or less (since, for example, the RTWs are needed in missions or must be kept available for missions) in accordance with the aforementioned requirement (reduction performance > 3 log levels).
The disinfection of RTWs must first be subject to the requirement of periodic / recurring disinfection, which - depending on the respective hygiene plan of the facility - is carried out daily to weekly. This measure is - as described above - very time-consuming when using wipes and against the background of the requirement for largely complete disinfection of all contact surfaces. In the case of an RTW of the Strobel Aalen system commonly used in the FRG, about 2 hours are required for this. During this time, the medical specialist is not available for medical procedures - which are often immediately necessary - but carries out basic medical work for 2 hours. At most, in the case of direct contamination (e.g., leakage of blood from a pressure-loaded vein during the placement of a peripheral indwelling access), indicated disinfection of small surfaces is provided for, which can then be performed in the range of minutes and is in no way comparable to periodic disinfection.
While the indicated disinfection of small surfaces as secondary or tertiary prevention, precisely indicated after the occurrence of contamination, can be effectively carried out immediately in a short time, there are great uncertainties with regard to periodic disinfection in the sense of primary prevention, i.e. the general reduction of infection risks, without directly knowing the cause (this is the decisive difference to the indicated disinfection of small surfaces, which must specifically cover a small manageable area, which is usually precisely known) (Nobile, Pasquarella et al. 2018).
Therefore, from the point of view of systematic, technical hygiene, periodic disinfection, considering the time axis and the "man-power" performing it, is a non-validated quantity and therefore to be considered uncertain. In the absence of other methods, only periodic disinfection / basic disinfection has been possible to date, and this is time-consuming and never completely feasible due to the nature of the application (human bias / wetting gaps due to wipes). Therefore, this process cannot be validated and is unsafe (Farhadloo, Goodarzi et al., 2018).
This discrepancy had to be accepted until now, also taking into account that the lethality risk of the patient is usually higher when emergency treatment is used than the risk of infection spread. However, this quite viable interpretation does not include the risk of infection to which the personnel performing the necessary medical measures on the patient are exposed.
Even alternative procedures of periodic disinfection do not close the "disinfection gap" between the applications of the just periodic disinfection procedure. One such procedure is hydrogen peroxide aerosol disinfection (Farhadloo, Goodarzi Far, 2018; Andersen, Rasch et al. 2006). Although a much greater wetting depth is achieved here with largely mechanical application of an aerosol than with manual wipe disinfection, the procedure can only be carried out in the absence of staff and patients - i.e. periodically. Furthermore, these measures are more time-consuming than manual wipe disinfection, since contact time and airing time must be taken into account. Therefore, the downtime of the vehicle during the measure is larger (often such a disinfection requires 3 to 4 hours).
There is and remains an increased risk of infection, simply because indicative rapid disinfection and periodic wipe disinfection and also periodic disinfection by apparatus, e.g. with hydrogen peroxide aerosol, cannot close the "disinfection gap" described above.
The plasma disinfection process in the "PLASMOCAR®" device can close this "disinfection gap". The process emits disinfection-active components of an electrophysical reaction of atmospheric oxygen with water vapor in the air. Compared to filters, the air does not have to be conveyed through the device at a defined exchange rate. Rather, the disinfection-active components are emitted into the room air, which leads to germ activation in the air and the surfaces in contact with air. This breaks aerogenic infection chains and smear infections (primarily fecal-oral and hematogenic in this case) infection chains (Aboubakr, Williams et al. 2015; Ahlfeld, Boulaaba et al., 2015; Ehlbeck, Schnabel et al. 2011).
The process can be used permanently, so that simultaneous disinfection/continuous disinfection of air and surfaces is achieved. Wetting gaps are no longer relevant here, since the disinfection-active components are diffusely distributed in the room air of the ambulance and thus reach all surfaces, including those that cannot be reached in a reasonable time by wipe disinfection. The "human bias" is also eliminated, i.e. the procedure can be standardized and validated, analogous to disinfection of dishes or instruments using equipment.
The purpose of this study was to demonstrate possible applications and limitations of cold plasma for disinfection in emergency medical services. PLASMOCAR® from WK-Medtec GmbH was used for this purpose.