False positive results of Bowie and Dick type test used for hospital steam sterilizer with slower come-up ramps: A case study

Steam quality monitoring as a strategy to reduce wet packs and sterilization failure

BACKGROUND

Hospital articles processed by steam are widely used in the Central Sterile Supply Department (CSSD), responsible for due sterilization. Steam sterilization is discussed worldwide, aiming to protect patients. If steam is outside the specified requirements, the sterilization process may fail, resulting in the wet packs at the end of the sterilization cycle.

METHODS

The present study evaluated the steam quality at Santa Catarina Hospital (São Paulo, SP, Brazil) from 2016 to 2022. Saturated steam containing noncondensable gases, excess condensate, or even superheat was characterized using the methodology indicated in the European Standard EN 285:2015.

RESULTS

From 2016 to 2020, qualification tests showed that the saturated steam quality does not achieve standard limit parameters. Infrastructural maintenance actions were taken to adjust the saturated steam quality. In 2021, the steam quality followed technical standards, and its adequacy was confirmed in 2022.

CONCLUSIONS

The points developed by the hospital's maintenance department, the adoption of appropriate devices for this purpose, and the correct preventive maintenance in the autoclaves, together with the correct qualification of the equipment and proof of the steam quality, contributed to improve the safety of the hospital sterilization process and reduce the incidence of wet packages.

Performance evaluation of the sterilization process with Bowie & Dick test and biological indicator in the quality control of a blood bank in Peru

Managing contaminated waste in blood banks is a crucial process that must end with the safe disposal of blood products. In this sense, practical methods and indicators must be used to guarantee the operability of autoclave equipment and the sterility of treated waste to mitigate the risk of biological exposure and hospital biosafety. We designed a cross-sectional study to evaluate the performance the autoclaving process with Bowie & Dick test and biological indicator at the Hemotherapy and Blood Bank Unit of the Cayetano Heredia Hospital in Peru. Fifty autoclaving processes were carried out independently for the Bowie & Dick tests and biological indicators based on Geobacillus stearothermophilus spores. Autoclaving was programmed at 134°C for 3.5 minutes for the Bowie & Dick test, while, for the biological indicator, it was programmed at 121°C for 5 minutes. Both in the presence of contaminated waste. The autoclaving process evaluated by the Bowie & Dick test had a compliance rate of 80% (CI95: 66.3%-90.0%), while, by the biological indicator, 90% (CI95: 78.2%-96.7%). We did not find significant differences between the results of both tests (P = .689; Fisher exact test). The compliance rate in the autoclaving process within the blood bank of a Peruvian Hospital is acceptable; however, there are actions for continuous improvement, especially at the vacuum level in the autoclaving process.

Analysis of water quality over non-condensable gases concentration on steam used for sterilization

Background

Non-condensable gases (NCGs) are all gases that do not undergo liquefaction during the saturated steam sterilization process. During a sterilization cycle, the NCGs presence inside the chamber is one of the biggest threats to the sterilization process compromising process validation and product quality.

Methods

In this work, 170 testing of NCGs concentrations performed between September 2016 and August 2021 were carried out by Orionce Serviços de Metrologia Ltda (Barueri, SP, Brazil), according to EN285:2015 procedure. For steam generation, the types of water used were softened water (SW), one-step reverse osmosis (RO), purified water (PW), and water for injection (WFI). The data obtained were analyzed using Minitab^® software, version 18.1, to identify a relationship between the water quality used for steam generation and the concentration of non-condensable gases determined into equipment qualification.

Findings

From total tests performed, 109 tests passed, and 61 tests failed, representing 64.2% and 35.8%, respectively. A higher failure rate was observed in terms of concentration of non-condensable gases in systems that used purified water for steam generation (64.7%), followed by softened water (55.6%), one-step reverse osmosis (42.9%), and water for injection (7.6%).

Conclusion

System processes using WFI for steam generation showed better results for steam quality approvement, in terms of NCGs concentration, compared to softened, purified, or reverse osmosis water treatments in the concentration of non-condensable gases in steam used for sterilization processes of industrial utilities.

Reusability of autoclaved 3D printed polypropylene compared to a glass filled polypropylene composite

Health care waste can be a costly expenditure for facilities as specific disposal methods must be used to prevent the spread of pathogens. If more multi-use medical devices were available, it could potentially relieve some of this burden; however, sterilization between uses is important in preventing disease transmission. 3D printing has the ability to easily create custom medical devices at a low cost, but the majority of filaments utilized cannot survive steam sterilization. Polypropylene (PP) can withstand autoclave temperatures, but is difficult to print as it warps and shrinks during printing; however, a composite PP filament reduces these effects. Commercially available PP and glass filled PP (GFPP) filaments were successfully 3D printed into 30 × 30 × 30 mm cubes with no shrinking or warping and were autoclaved. The 134 °C autoclave temperature was too high as several cubes melted after two to three rounds, but both PP and GFPP cubes displayed minimal changes in mass and volume after one, four, seven, and ten rounds of autoclaving at 121 °C. GFPP cubes autoclaved zero, four, seven, and ten times had significantly smaller average compressive stress values compared to all PP groups, but the GFPP cubes autoclaved once were only less than PP cubes autoclaved zero, seven and ten times. GFPP cubes autoclaved zero, one, four, and seven times also deformed less indicating that the embedded glass fibers provided additional strength. While a single method was found that successfully printed PP and GFPP cubes that were able to survive up to ten rounds of autoclaving, future work should include further investigation into the mechanical properties and increasing the number of autoclave rounds.

Sensors in the Autoclave-Modelling and Implementation of the IoT Steam Sterilization Procedure Counter

Surgical procedures involve major risks, as pathogens can enter the body unhindered. To prevent this, most surgical instruments and implants are sterilized. However, ensuring that this process is carried out safely and according to the normative requirements is not a trivial task. This study aims to develop a sensor system that can automatically detect successful steam sterilization on the basis of the measured temperature profiles. This can be achieved only when the relationship between the temperature on the surface of the tool and the temperature at the measurement point inside the tool is known. To find this relationship, the thermodynamic model of the system has been developed. Simulated results of thermal simulations were compared with the acquired temperature profiles to verify the correctness of the model. Simulated temperature profiles are in accordance with the measured temperature profiles, thus the developed model can be used in the process of further development of the system as well as for the development of algorithms for automated evaluation of the sterilization process. Although the developed sensor system proved that the detection of sterilization cycles can be automated, further studies that address the possibility of optimization of the system in terms of geometrical dimensions, used materials, and processing algorithms will be of significant importance for the potential commercialization of the presented solution.

Performance evaluation of chemical, biological and physical indicators in the process of sterilization under the effect of non-condensable gases

BACKGROUND

The risk concerning the presence of non-condensable gases (NCGs) has already been demonstrated, but routine monitoring still requires further research to be implemented in each sterilization cycle.

AIM

Performance evaluation of the physical, chemical and biological indicators used in monitoring in comparison with a sterilizer integrated detector for NCG in the Sterilization Process.

METHODS

Chemical indicators (type 2 Bowie-Dick test, type 5 and type 6 models), self-contained biological indicators and physical indicators (temperature, pressure, thermal qualification and a patented integrated air detector) were used to monitor the steam sterilization process in two situations of controlled failure: chamber leakage and door seal failure. This controlled failure was obtained by the presence of a known amount of air: 0-30 L/min for chamber leakage and 0-30% for the door seal failure. Evaluation tests were carried out with and without the use of process challenge devices (PCDs).

FINDINGS

In both studies, the Bowie-Dick Test showed different results, according to the manufacturer. The biological, physical or chemical indicators without a PCD were unable to detect small volumes of NCGs in both simulations.

CONCLUSION

The integrated air detector can be considered an option for the detection of NCGs in each cycle.

Low-cost biofuel-powered autoclaving machine for use in rural health care centres

Surgical site infections (SSIs) in developing countries have been linked to inadequate availability of sterilising equipment. Existing autoclaves are mostly unaffordable by rural healthcare practitioners, and when they managed to procure them, the electricity supply to power the autoclaves is epileptic. The solar-powered autoclave alternatives are too bulky with a very high initial cost. Hence, low-cost biofuel-powered autoclave becomes an attractive option, and this study sought to present the design, development and clinical evaluation of the device performance. With the global drive for the adoption of green energy, biofuel will not only reduce greenhouse gas emission but also provide revenue for local producers and reduce biomass associated health complications. The theoretical energy requirement for the sterilisation process was calculated. The standard pressure and temperature needed for sterilisation were tested to be 121 °C and 15 psi. The device was also clinically tested with Staphylococcus aureus bacteria obtained from the Department of Medical Microbiology and Parasitology, University of Ilorin Teaching Hospital using Brain heart Infusion Broth, MacConkey and Blood agar as cultured media. No bacteria growth was observed when the samples containing the bacteria colony were autoclaved by the designed autoclave and incubated at 37 °C for 2 d. Hence, the device met the mechanical and biological validation standards for effective sterilisation.