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

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.

Specialists' opinion regarding factors related to wet loads after steam sterilization

BACKGROUND

Episodes of wet loads after steam sterilization are frequent, however, the factors related to these events are still unclear.

AIM

Evaluate the strength of relationship of factors related to wet loads after steam sterilization.

METHODS

By adapting the Delphi technique, steam sterilization specialists assigned a score for the relation strength of a list of 37 factors (f.01-37) related to wet load, grouped into: cycle parameters, sterilizer, steam, load and environment. 67 specialists distributed on 5 continents participated in all phases of this study.

FINDINGS

Certain factors related to wet loads are better established, such as vacuum depth in the drying phase, while others are still controversial, such as those related to the environment. The factor that obtained the highest average score was the vacuum depth in the drying phase (f.12), with a value of 4.28, while the lowest score of 2.66 was obtained in the delay time when the set reaches the value of vacuum or steam in the conditioning phase (f.05).

CONCLUSION

Specialists' opinions diverge in most of the factors related to the occurrence of wet loads. The results obtained will allow to direct new research and normative requirements.