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Nov 19, 2020

Executive Summary – Regina Guttenberger

Regina Guttenberg, Masterstudent at OTH Amberg-Weiden

Infections are a serious matter that can quickly affects all of us and can have significant, protracted consequences. Well-known studies have long since proven that there are several correlating factors for wound infections. With the increasing risk of antibiotic resistance causing prophylactic treatments to become increasingly ineffective, an ever-increasing global problem arises. Therefore, alternative measures must be strengthened and, for example, ventilation systems as part of infection prevention must be as effective as possible. Currently, there are many differences in test methods internationally and no uniform standards that are used for the qualification of ventilation systems in hospitals. A basic distinction is made between particles and microbiological test methodologies. However, it can be said that there is currently no internationally valid standard that recommends clearly formulated test methods for testing the microbial contamination of the air to validate ventilation systems in operating theatres as part of the performance qualification. 

The aim of the thesis was to be able to experimentally draw a conclusion about the relevance of the test procedures and the effectiveness of OR ventilation systems by means of suitable data analysis. In addition, the effectiveness of several surgical ventilation systems has been assessed, by means of an assessment matrix. 

Four different test methods by means of experimental investigations have been evaluated and to conclude a statement about their relevance regarding the effectiveness of three different technologies of operating room ventilation systems. During the execution of the test methods, the particle concentration and the cfu (colony-forming unit) concentration were determined simultaneously at the same measuring positions as specified in the respective test method. The experiments were performed with the conventional ventilation systems of laminar airflow (LAF), turbulent-mixed ventilation (TMV) and the new developed temperature-controlled airflow (TcAF) technology. The assessment of the test methods was made with the help of a data analysis and an assessment matrix of defined criterions. 

The results of the experiments showed no correlations between the cfu concentrations and the particle concentrations. Findings of the data analysis revealed a great disparity between test methods that create ideal conditions, performed in an empty operating room without people and test methods that are performed intra-operative. 

There are currently international many different test methods regarding particle measurements. Thus, there are several possibilities to test the validation process of hospital ventilation systems using particle measurements for the Operation Qualification (OQ) of empty rooms. They all use particles with the size 0.5 μm. However, the size distribution of microbiological pathogens is much larger, and this difference is seemingly neglected. From a technical point of view, measuring particle concentration is sufficient to assess how effectively a ventilation system works under ideal conditions, without considering real factors such as surgical staff, their behaviour or equipment used. 

It is therefore advisable to make a clear distinction between the test methods within the technical release and the Operation Qualification and to make an assessment under real conditions in regular intervals within the in Performance Qualification. The test methods that are performed under ideal conditions are solely assessing the efficacy of a ventilation system, should thus be separately from test methods that are performed intraoperatively and assessing the effectiveness of ventilation systems. In contrast to this, there are currently only a few microbiological test methods that can be carried out as part of a Performance Qualification during actual surgery. The effectiveness of surgical ventilation systems is more accurately assessed with intraoperatively applied microbiological test methods than any values recorded under ideal conditions in empty rooms. The awareness of airborne pathogen reduction as a form of infection prevention – and the increasing role of the effectiveness for OR ventilation systems to keep it low – should be raised to create united viewpoints and internationally aligned test methods. 

Furthermore, it should be noticed that the size distribution of microbiological pathogens is much larger, than the size of particles, which is investigated within particle measurements. It would also be useful to apply internationally uniform standards to be able to make better comparisons and to establish a worldwide basic standard

As antibiotic resistance increases, the effectiveness of prophylactic measures decreases. Preventive procedures, such as hospital ventilation systems, are therefore playing an increasingly important role. If the effectiveness of an OR ventilation system is to be evaluated, this study shows that the focus should be on reducing pathogens in the air. 

Remember that it is always a viable particle like a bacterium, carried by a particle, that will cause the infection.


This article is awarded with IKMH Förderpreis 2020