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(e) Rotheudt, H., Lichtner, E., Brockmann, G., Hofera, V., Askan, T. Hartmann, A., Zielke, B. & Kriegel, M. (2018)

Distribution of Microbial Contamination in Operating Theaters and Healthcare Environments. In: Proceedings 24th International Symposium on Contamination Control and Cleanroom Technology, The Hague, Netherlands, Sept 23-26.

Most investigations and the standard acceptance test cases consider particle contaminant of small particle size that is completely airborne without gravitational effects. Brownian diffusion has the greatest impact on small particles. Bacteria carrying particles are mainly in the range of medium sized particles that are affected by turbophorensis and interception, or in the range of large particles that are highly influenced by gravity. Microbial contaminants are thus affected by their gravitational settling and do not perfectly follow the airflow motion. Gravitational forces lead to significantly increase their deposition behavior. Therefore, investigations that consider the microbial particulates as completely airborne have limited validity to predict the surface contamination inside patients wound field or on medical instruments.

(d) Zielke, B., Hofer, V., Rotheudt, V., Rischmüller, S., Brockmann, G. & Kriegel, M. (2017)

Experimental Investigation of Airborne Particle Distribution in Operating Theatres under Realistic Load Configuration: A – Developing an Operating Personnel Dummy with Realistic Posture and Particle Emission. Presented on Healthy Buildings 2017 Europe, Lublin, Poland, July 2-5.

To evaluate different airflow patterns regarding their ability to protect the patient from airborne contamination, the use of realistic contamination sources, flow obstacles and heat loads is fundamentally important. Over- simplistic arrangements are often used to evaluate the effectiveness of OR ventilation. For example, according to the German standard on operating rooms (DIN 1946-4), it is assumed that the personnel stand upright beside the patient and that the particle sources are located on the floor. Thus, for the evaluation of an OR air flow concept, the use of a realistic personnel dummy is essential for two reasons: firstly, because the personnel are the main source of germs and those are distributed not only at floor level, and secondly because the personnel have a significant effect on the airflow by being an interruption into the path of air when bending over the patient.

(c) Sadrizadeh, S., Holmberg, S, (2015)

Impact of staff posture on airborne particle distribution in an operating theatre equipped with ultraclean-zoned ventilation. 36th AIVC Conference “Effective ventilation in high performance buildings”, Madrid, Spain, 23-24 September 2015.

Usually, operating room ventilation ventilation performance is determined without considering the influence of staff-member posture and movements. Results indicate that bending posture increases the overall number of suspended particles in the surgical area by disrupting the particle-free airflow.

(b) Cristina, M. L., Spagnolo, A. M., Sartini, M., Panatto, D., Gasparini, R., Orlando, P., Ottria, G. & Perdelli, F. (2012)

Can particulate air sampling predict microbial load in operating theatres for arthroplasty? PLOS One, 7(12)

Measuring airborne particle counts as an indirect indicator of the microbiological air quality in operating rooms is derived from cleanroom technology standards but has seldom been subjected to evaluation. In this study by Cristina et al. including 95 surgical arthroplasty procedures (59 hip replacements and 36 knee replacements), the aim was to determine whether particle counting could predict microbiological air contamination in an operating theatre. The results did not indicate any statistical correlation between microbial air contamination in terms of CFU/m3 and airborne particle counts for either of the particle diameters considered ( ≥ 0.5μm and 5μm) and the study concludes that microbiological air sampling remains the most suitable method for investigating the quality of air in operating theatres.

(a) Whyte, W., Lidwell, O. M., Lowbury, E. J. L., & Blowers, R. (1983)

Suggested bacteriological standards for air in ultraclean operating rooms. Journal of Hospital infection4(2), 133-139.

In this study from 1983, Whyte et al. states that bacteriological standards for the air in ultraclean operating rooms are needed since physical tests alone cannot guarantee satisfactory results. 10 cfu/m3 is suggested as the highest acceptable value for an ultraclean system since a substantial benefit can be obtained if the average concentration of airborne contamination do not is exceeded. Confirmation that the ultraclean air system has resulted in an acceptable low level of bacterial contamination of the air is therefore an essential precaution.

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