Study on hand disinfection in inpatient geriatric care on the superiority of cold plasma aerosol versus alcohol-based disinfection methods in a parallel group design

In the nineteenth century, the healthcare sector witnessed a revolution in hygiene practices, marked by the introduction of basic cleanliness, disinfecting handwashing, and sterilization of surgical instruments, which brought about a significant reduction in mortality rates. These methods are in line with the germ theory of infection causation^1,2. Further advancements introduced chemical and thermal sterilization, proper cleaning of textiles, and the utilization of disposable gloves. Leading institutes in the United States and Germany acknowledge hand hygiene as highly effective in preventing nosocomial infections³. The advent of alcohol-based disinfectants enhanced compliance with hand hygiene, thereby reducing healthcare-associated infections and antibiotic-resistant pathogens.

Hand hygiene is a fundamental measure for infection prevention, eliminating transient germs acquired through contact with patients and surfaces. Alcohol serves as the active ingredient, with concentrations of 60–80% alcohol sufficing for routine use, while 99% alcohol is necessary for specific viruses such as Noroviruses. However, acceptance of hand disinfection in nursing homes remains low, often attributed to factors such as convenience, lack of training, time constraints, skin problems, and lack of awareness^4,5.

Research by Smith et al. and Cordeiro et al.^6,7 revealed that hand hygiene compliance among staff in long-term care facilities averages around 14%, with variations observed before and after patient contact. Using real data on Norovirus transmission, Assab and Temime demonstrated that raising this compliance rate to 60% could result in a 75% reduction in gastrointestinal diseases among residents within 100 days⁸. A Cochrane Review by Gould et al. reported mixed results concerning the effectiveness of interventions designed to improve hand hygiene, with most increases being modest yet significant. Despite the inability to isolate the most effective intervention, all measures appear to contribute to some degree in enhancing hand hygiene compliance, with the potential drawback of resource misallocation⁹.

A more nuanced perspective highlights unique challenges in infection control within long-term care facilities, with hygiene officers encountering difficulties in applying various recommendations (e.g. DGKH (German Society for Hospital Hygiene (Deutsche Gesellschaft für Krankenhaushygiene e.V.)), KRINKO (Commission for Hospital Hygiene and Infection Prevention at the Robert Koch Institute), DQNP (German Network for Quality Development in Nursing)) to their respective work areas. There is an urgent need for evidence-based hygiene guidelines tailored to these specific facilities and their legal relationships with residents. Standardization and monitoring by authorities and institutions such as KRINKO are also warranted. The revised Infection Protection Act (IfSG) now entrusts health authorities with oversight of outpatient nursing services and home-like service providers¹⁰.

Emerging studies reveal the potential of cold plasma hand disinfection in clinical and healthcare settings, positioning it as an alternative to conventional alcohol-based hand disinfection^11,12,13. The use of cold plasma not only minimizes skin exposure but also preserves skin integrity even after repeated applications, contributing to improved skin health¹³. Findings suggest that incorporating cold plasma disinfection could become a cornerstone in hospital and nursing home hygiene, particularly in care and treatment areas^11,12. Moreover, the technology presents substantial economic benefits and the potential for antimicrobial treatment of contaminated wounds and skin^12,13.

In cold plasma aerosol reactions (atmospheric low-temperature plasma), hydroxyl radicals are formed, which can alter the electrophysiological potential of microorganisms’ plasma membranes, disrupting transport processes and causing lethal damage^14,15. Secondary oxidation effects can also induce plasma membrane leakage, further compromising microorganism function¹³. These electrophysical effects underpin cold plasma’s antimicrobial properties (see Fig. 1). The aerosol’s liquid phase, enriched with plasma reaction products, ensures maximum dispersion in the gaseous phase¹⁴.

Cold plasma eliminates microorganisms by a short circuit of the membrane potential (own illustration based on¹⁵).

Notably, cold plasma poses no acute or chronic toxicity to eukaryotic tissues (plants, animals, and humans). This is attributed to the fact that antioxidant enzymes in these tissues neutralize plasma reaction products before they can cause harm to eukaryotic cells^12,13. The medical safety of cold plasma is supported by toxicity assessments, such as the Ames test (EN ISO 10993-3) and a Cytotoxicity test (EN ISO 10993-5), which the examined cold plasma process (in the form of PLASMOHAND) passed, showing no mutagenic effects in human cells. Furthermore, the ozone emissions from the examined device comply with regulatory standards, with a time-weighted average of 39 µg per cubic meter over eight hours, well below the 120 µg per cubic meter limit, thereby confirming its environmental compatibility¹⁶.

Atmospheric low-temperature plasma generates hydroxyl radicals from ambient air, which contains all essential reactants (oxygen and water vapor). The plasma reaction is an electrophysical process in which an ignition pulse renders the gas mixture conductive. A subsequent low current flow at a defined voltage and frequency induces the desired reaction of the atmospheric low-temperature plasma, producing effective hydroxyl radicals as reaction byproducts^17,18. This discovery has led to the development of a device that harnesses these principles for hand disinfection, encompassing the entire process within a single system¹⁸.

The aerosol application in the design of the device eliminates the problematic wetting gaps associated with alcoholic hand disinfectants, enabling more complete and homogeneous hand exposure. Residual moisture on hands does not interfere with the process, as studies indicate no adverse effects on plasma disinfection efficacy.

The current investigation aims to comparatively assess the disinfectant efficacy of the cold plasma aerosol under practical application conditions, in comparison to an alcoholic hand disinfectant listed in the VAH (Association for Applied Hygiene) list. The difference in efficacy between alcohol-based hand disinfection and cold plasma-based hand disinfection will be measured in terms of reduction in log colony-forming units. Additionally, the spontaneous occurrence of fecal indicators (Enterococcus spp.) and the presence of potentially infectiologically problematic bacteria (Staphylococcus aureus) on the hands will be examined.