Evaluating the effect of Novarerus NV800 air purifier units during orthopaedic surgery to reduce bioburden in the air.

BACKGROUND: A locally installed air purifier unit (Novaerus Protect 800) has been shown to reduce the air bioburden in an intensive care unit and the incidence of healthcare-associated infections. AIM: To explore whether this type of air purifying unit could reduce bacterial concentrations in the air of an operating room (OR) during orthopaedic surgery, thereby reducing the risk of surgical site infections. METHODS: In this prospective experimental study, undertaken in 2018, three air purifying units were installed in an OR in a Swedish hospital in 2018. The air was actively sampled during 11 operations by a slit-to-slit agar impactor with the air purifying units either switched on or switched off. Air movements were visualized with the aid of smoke in mock-up studies. FINDINGS: No significant difference in bacterial concentrations in air was found between the two conditions (air purifying units switched off or on) (P=0.54). Air movements around and above the surgical wound were disordered and resembled those of dilution mixing air. CONCLUSION: The three air purifying units installed in the OR did not reduce the airborne bacterial levels in the critical zone during orthopaedic surgery.

Source strength as a measurement to define the ability of clean air suits to reduce airborne contamination in operating rooms.

BACKGROUND: Surgical site infections after total hip and knee replacement are linked to the quality of the operating room (OR) air. Applying tight occlusive clothing, effective ventilation and correct working methods are key concepts to obtain low bacterial concentrations in the OR air. The dry penetration test referred to in European standard EN 13795-2:2019 is a screening method for materials used in surgical clothing. Source strength, defined as the dispersal of bacteria-carrying particles from persons during activity, is a functional test of clothing systems and has been calculated in a dispersal chamber and in ORs. Results from both tests can be used when comparing surgical clothing systems. AIM: This study relates results of dry penetration tests to source strength values for five surgical clothing systems available on the Swedish market. METHODS: Experimental data are reported on the function of these products, expressed as source strength calculated from results in a dispersal chamber and in ORs during orthopaedic operations. FINDINGS: All materials tested with dry penetration ≤50 colony-forming units (cfu) had source strength values <3 cfu/s for one person in the dispersal chamber, whereas the material of one product when laundered >50 times had source strength in the dispersal chamber of up to 8 cfu/s. CONCLUSION: The dry penetration test could predict the performance of clean air suits of the same design, but more studies are needed to obtain a more valid correlation. Requirements of source strength should be included in standards.

Ventilation design conditions associated with airborne bacteria levels within the wound area during surgical procedures: a systematic review.

BACKGROUND: Without confirmation of the ventilation design conditions (typology and airflow rate), the common practice of identifying unidirectional airflow (UDAF) systems as equivalent to ultra-clean air ventilation systems may be misleading, but also any claims about the ineffectiveness of UDAF systems should be doubted. The aim of this review was to assess and compare ventilation system design conditions for which ultra-clean air (mean <10 cfu/m3) within 50 cm from the wound has been reported. Six medical databases were systematically searched to identify and select studies reporting intraoperative airborne levels expressed as cfu/m3 close to the wound site, and ventilation system design conditions. Available data on confounding factors such as the number of persons present in the operating room, number of door openings, and clothing material were also included. Predictors for achieving mean airborne bacteria levels within <10 cfu/m3 were identified using a penalized multivariate logistic regression model. Twelve studies met the eligibility criteria and were included for analysis. UDAF systems considered had significantly higher air volume flows compared with turbulent ventilation (TV) systems considered. Ultra-clean environments were reported in all UDAF-ventilated (N = 7) rooms compared with four of 11 operating rooms equipped with TV. On multivariate analysis, the total number of air exchange rates (P=0.019; odds ratio (OR) 95% confidence interval (CI): 0.66-0.96) and type of clothing material (P=0.031; OR 95% CI: 0.01-0.71) were significantly associated with achieving mean levels of airborne bacteria <10 cfu/m3. High-volume UDAF systems complying with DIN 1946-4:2008 standards for the airflow rate and ceiling diffuser size unconditionally achieve ultra-clean air close to the wound site. In conclusion, the studied articles demonstrate that high-volume UDAF systems perform as ultra-clean air systems and are superior to TV systems in reducing airborne bacteria levels close to the wound site.

Airborne viable particles and total number of airborne particles: comparative studies of active air sampling.

This paper presents results from a comparative study of different impaction air samplers under simulated operational conditions in a controlled environment. Furthermore measurements have been performed in a body-box during evaluation of clean-room clothing and in a day care center. Microbial monitoring of controlled environments can be performed in several ways, and with the aid of different sampling instruments. Knowing the limitations of the chosen system is of vital importance for the correct evaluation and interpretation of the results. The number of Colony Forming Units (CFU) detected by one method cannot be directly compared with results from another method. The obtained results seem to indicate that in a controlled environment the exposure situation with a human contamination source gives an approximate relationship between the total number of airborne particles and the number of aerobic airborne viable particles detectable with standard methods.

Design of HEPA-filters above autoclaves and freeze-dryers.

In pharmaceutical manufacturing some processes and process equipment cause temperature differences relative to the surrounding air, e.g. sterilisation and freeze-drying processes. Generally there is a temperature difference when a door to such equipment is opened. This can cause a flow of room air through the opening, creating a contamination risk, especially when manual handling of material is performed in this area. To minimize this risk, a HEPA-filter unit should be installed above the opening to provide clean air and protect the opening. The airflow needed through the HEPA-filters depends mainly on the temperature difference between the chamber and the room and the size of the opening. The flow of clean air should be greater than that of the theoretically calculated flow in order to minimize contamination hazards. In this paper the theoretical relations are discussed and design criteria are presented in a simplified form with graphical representations. Results from a case study are described and the experimentally estimated air-flow values are compared with the theoretically calculated values.

Qualification of weighing station for pharmaceutical substances.

Work at weighing stations in pharmaceutical industries can cause risk situations to the operators as well as to the product. When working at a station, the operators' movements and the interaction between air movements and dispersion of contaminants play a vital role. A newly designed ventilated weighing station with HEPA-filters and how it can be evaluated with tracer gas will be discussed.

Hazard analyses of airborne contamination in clean rooms--application of a method for limitation of risks.

Hazard Analyses and establishing of Critical Control Points (HACCP) using a method with Limitation of Risks, known as the LR Method are described. This method has a concept involving visualization of air movements, particle challenge testing and calculation of a risk factor. The calculated risk factor and the estimated exposure time form the basis for the HACCP. The LR Method can also be used as an engineering tool to achieve microbiologically safe processes with regard to airborne contamination. As an alternative to the increasing extent of microbiological monitoring sampling, a system is discussed that combines continuous monitoring of particle levels with particle counters and a limited monitoring of viable particles with air samplers.

Single-use surgical clothing system for reduction of airborne bacteria in the operating room.

It is desirable to maintain a low bacterial count in the operating room air to prevent surgical site infection. This can be achieved by ventilation or by all staff in the operating room wearing clothes made from low-permeable material (i.e. clean air suits). We investigated whether there was a difference in protective efficacy between a single-use clothing system made of polypropylene and a reusable clothing system made of a mixed material (cotton/polyester) by testing both in a dispersal chamber and during surgical procedures. Counts of colony-forming units (cfu)/m(3) air were significantly lower when using the single-use clothing system in both settings.

The biotest RCS air samplers in unidirectional flow.

When monitoring the microbiological quality of air in unidirectional air flow units the Biotest air sampler Reuter Centrifugal Sampler (RCS) is often used. In this unidirectional air flow the dispersion region of contaminants (disturbance region caused by turbulence) around the RCS sampler is much larger than that of undisturbed parallel air flow. The recently developed air sampler from Biotest, the RCS+, has a smaller and a different type of dispersion region (disturbance region) than that of the common RCS sampler. The differences must be taken into consideration when the two types of RCS air sampler are used within unidirectional air flow units, especially during aseptic operations in pharmaceutical production.

Interaction between air movements and the dispersion of contaminants: clean zones with unidirectional air flow.

The purpose of this presentation is to describe the theoretical relations for the dispersal of airborne contaminants and to illustrate the validity of these equations occurring during factual situations, where a number of observations on air movements in open unidirectional air flow units supplied with HEPA-filters are described. In factual situations the aerodynamic system which governs the dispersion of contaminants in reality is always very complicated that risk situations must be mapped and assessed empirically. The presence of a person can give risk to wakes that may be stable or unstable. The unstable situations are in most cases caused by the influence of arms and hands. As part of the microbiological assessment of aseptic processes carried out in clean zones, it is important to investigate that such vortices do not occur in the clean working areas. As the level of airborne contaminants in the operational environment may have an effect on the level of product contamination, the microbiological assessment of aseptic processes is important. A system is described for microbiological assessment in unidirectional air flow units by using visual illustrative methods and particle challenge tests (measured by particle counter) for the dispersion and/or induction of particles.

Some aspects on the use of the Biotest RCS Air Sampler in unidirectional air flow testing.

The Biotest Air Sampler RCS is often used for monitoring microbiological quality of air. Unidirectional air flow tests show that the dispersion region of contaminants around the RCS sampler is much larger than that of undisturbed parallel air flow. This must be taken into consideration when the RCS air sampler is used within pharmaceutical production, especially during aseptic operations.