In the 19th century, the foundations for understanding hygiene in healthcare were established. Measures such as basic cleanliness for wounded soldiers, disinfecting handwashing in maternity wards, and the sterilization of surgical instruments and patient environments led to a dramatic reduction in mortality rates. These practices align with the germ theory of infection causation [1]. Advances in various fields introduced chemical and thermal sterilization methods, cleaning textiles with appropriate temperatures and detergents, disinfecting handwashing, and the use of disposable gloves. Leading institutes in the USA and Germany, assessing hand hygiene a century after Semmelweis and Koch, consider it highly effective in preventing nosocomial infections and the most effective individual measure for interrupting infection chains [2; 3]. The shift to alcohol-based, skin-friendly disinfectants increased compliance with hand hygiene rules, leading to time savings and subsequently reducing healthcare-associated infections and antibiotic-resistant pathogens.
Hygienic hand disinfection is regarded as a central, cost-effective, and fundamental measure for infection prevention. Its proper implementation serves as a visible quality indicator for inpatient care facilities. The often-cited time loss during this measure is considered an unsubstantiated argument. Staff responsibility for the correct execution of all care measures ensures resident safety. Cross-infections occur in up to 80 percent of cases through hands. Hygienic hand disinfection aims to eliminate transient germs that reach the skin through contact with residents, visitors, surfaces, and objects (constantly changing germ spectrum). Alcohol is used as the active ingredient for hand disinfection, with "limited virucidal" agents (60–80% alcohol) being sufficient for routine use. For efficacy against specific viral agents such as Noroviruses, the use of a designated virucidal hand disinfectant (99% alcohol) is mandatory. The acceptance of hygienic hand disinfection in nursing homes remains low, often being inadequately performed. Hence, there is an urgent need to improve both the quality and frequency of hygienic hand disinfection. Major reasons for the low acceptance, identified by Manger-Kogler and Unterköfler, include convenience/forgetfulness (61%), lack of training/ignorance (42%), time pressure/lack of time (35%), skin problems (22%), and lack of awareness (17%) [4]. Studies by Hammerschmidt and Manser showed that the actual compliance of hand hygiene depends on the availability of disinfection devices during care in residents' rooms and bathrooms. Nurses hold different views on knowledge, perceived behavior, and perceived attitude toward hand hygiene. Organizational measures, such as the prohibition of using alcoholic disinfectants in residents' rooms, hinder hygiene, as the risk of poisoning a resident with disinfectants is perceived as more real than the possibility of nosocomial infection [5].
Smith et al. concluded that the average hand hygiene compliance rate of staff in long-term care facilities is only about 14.7% [6]. Similar results were found by Cordeiro et al., with an average hand hygiene compliance rate of 14.4%, varying with 4.8% before patient contact and 53.7% after patient contact, among other differentiation aspects [7]. Assuming these findings, Assab and Temime (2016) incorporated real data on the spread of the Norovirus into a mathematical model, demonstrating that an increase in hand hygiene compliance rate by 45 percentage points to 60% could reduce the expected cases of gastrointestinal diseases among residents by 75% within 100 days [8].
Gould et al., in their Cochrane Review, found significant differences in hand hygiene compliance, regardless of the type of intervention. Most increases in hand hygiene compliance in the intervention groups were small (less than 20% in observed compliance), though larger than increases in the control groups. Due to the variability of results, no conclusion could be drawn regarding which interventions or combinations of interventions lead to clinically significant improvements in hand hygiene compliance or a reduction in infection or colonization rates and under what circumstances. The role of hand hygiene could not be separated from the effects of other measures. However, it appears that all measures potentially contribute to some improvement in hand hygiene compliance, with the greatest harm lying in the use of resources that could have been utilized elsewhere [9].
A differentiated view highlights significant differences in the everyday challenges of infection control in long-term care facilities. Hygiene officers in these facilities struggle to assess the relevance of various recommendations (DGKH, KRINKO, and DQNP) and interpret them for their work areas. There is an urgent need for current hygiene recommendations that consider the specific situation in long-term care facilities and are based on existing evidence, considering the legal relationship between facilities and residents. Standardization of hygiene in facilities by authorities and monitoring institutions, such as KRINKO, is also necessary. The current amendment of the Infection Protection Act (IfSG) poses new challenges to health authorities, as they must now also oversee the infection control of outpatient nursing services and companies offering home-like services [10].
Current studies on cold plasma hand disinfection indicate that this procedure offers promising prospects in the clinical and healthcare sector [11; 12; 13]. Various studies have intensively discussed the potential of plasma disinfection as a possible alternative to conventional alcohol-based hand disinfection. A major advantage is that the use of cold plasma not only leads to a reduction in skin exposure, but also does not alter the integrity of the skin even after multiple applications [13]. The findings suggest that the implementation of cold plasma disinfection could become a permanent fixture in the hygiene of hospitals and nursing homes [12]. Especially using plasma devices in care and treatment rooms, hand disinfection using cold plasma could make an important contribution to infection prevention [11; 12]. In addition to the benefits for skin health, other studies point to the enormous economic potential of cold plasma disinfection [12; 13]. One promising aspect that is attracting the interest of researchers and experts alike is the possibility of using cold plasma to antimicrobially rehabilitate skin and contaminated wounds.
Effect of Cold Plasma Aerosol
In antimicrobially effective products resulting from a cold plasma aerosol reaction (atmospheric low-temperature plasma), hydroxyl radicals emerge. These radicals are capable of altering the electrophysical potential at the plasma membrane of microorganisms, including viruses. As a result, there is a disruption of transmembrane transport processes, leading to a halt in the exchange between extracellular and intracellular environments, causing the microorganism to be lethally damaged and perish.
Furthermore, secondary oxidation effects lead to leakage in the plasma membrane (primarily through the oxidation of unsaturated fatty acids in membrane lipids), resulting in a collapse of the entire electrophysical gradient across the plasma membrane. The antimicrobial effect is therefore primarily based on electrophysical effects that disrupt the function of microorganisms (Fig. 1).
<<Figure 1. Cold plasma eliminates microorganisms by a short circuit of the membrane potential.>>
In addition to the byproducts of the plasma reaction, an aerosol containing sterile water is introduced. The aerosol is based on a liquid (sterile water). Plasma reaction products are dissolved within the aerosol droplets, characterized by a highly dispersed distribution. This process enriches the liquid phase with plasma reaction products, which concurrently exhibit maximal dispersion in the gaseous phase.
Medical Safety
It is pertinent to note that there is no discernible acute or chronic toxic impact on higher organisms (eukaryotic tissues: plants, animals, humans). This lack of effect can be attributed to the presence of antioxidant enzymes (catalase, superoxide dismutase, alpha-1 antitrypsin) within these tissues and organisms, which effectively neutralize plasma reaction products before any detriment to the plasma membrane of these cells is conceivable.
Toxicological Safety
To substantiate the medical rationale, toxicity assessments can provide support. As an example, toxicity tests such as an Ames test (conducted in accordance with EN ISO 10993-3) and a Cytotoxicity test (conducted following EN ISO 10993-5) were carried out for the cold plasma process underpinning PLASMO®HAND. Both assessments revealed the absence of any mutagenic effects in human cells.
In accordance with the 39th Regulation Implementing the Federal Immission Control Act (BlmSchV), the ozone emissions of PLASMOHAND were assessed. The maximum recorded ozone concentration, as a time-weighted average over eight hours, is 39 micrograms per cubic meter, thus well below the recommended limit of 120 micrograms per cubic meter. This finding underscore compliance with prescribed emission standards and confirms the environmental compatibility of PLASMOHAND in accordance with prevailing regulations.
Principle of Operation for Disinfection with PLASMOHAND
Hydroxyl radicals are generated from ambient air through an atmospheric low-temperature plasma. The ambient air contains all necessary reactants for the plasma reaction in the form of oxygen and water vapor. The plasma reaction is an electrophysical process: an ignition pulse renders the gas mixture conductive. A low current flow at a defined voltage and frequency subsequently induces the desired reaction of the atmospheric low-temperature plasma, resulting in the production of effective hydroxyl radicals as reaction byproducts.
The identification of the disinfectant properties of plasma reaction byproducts has led to the consideration that these products can also be utilized for hand disinfection. In this context, a system has been developed that integrates the aforementioned principles into a single device [14].
The device is configured in the form of a box into which hands are introduced under a "no-touch" principle, automatically activating the device. Over an eight-second duration, hands with spread fingers are exposed to the aerosol containing plasma reaction byproducts. Subsequently, the disinfection process is completed.
The application of the aerosol in the design of the device avoids the well-known and problematic wetting gaps associated with alcoholic hand disinfectants. Therefore, the device allows for a largely complete and homogeneous exposure of the hands.
Moreover, residual moisture on the hands following prior handwashing is not problematic here; internal investigations have indicated that the efficacy of the plasma disinfection process is not adversely affected.