Operating Theatre Ventilation Systems and Their Performance in Contamination Control: “At Rest” and “In Operation” Particle and Microbial Measurements Made in an Italian Large and Multi-Year Inspection Campaign

Abstract

In Operating Theatres (OT), the ventilation system plays an important role in controlling airborne contamination and reducing the risks of Surgical Site Infections (SSIs). The air cleanliness is really crucial in this field and different measurements are used in order to characterize the situation in terms of both airborne microbiological pollutants and particle size and concentration. Although the ventilation systems and airborne contamination are strictly linked, different air diffusion schemes (in particular, the Partial Unidirectional Airflow, P-UDAF, and the Mixing Airflow, MAF) and various design parameters are used, and there is still no consensus on real performance and optimum solutions. This study presents measurements procedures and results obtained during Inspection and Periodic Performance Testing (1228 observations) in a large sample of Italian OTs (175 OTs in 31 Italian hospitals) in their operative life (period from 2010 to 2018). The inspections were made after a cleaning procedure, both in “at-rest” conditions and “in operation” state. Inert and microbial contamination data (in air and on surfaces) are analyzed and commented according to four relevant air diffusion schemes and design classes. Related data on Recovery Time (RT) and personnel presence were picked up and are commented. The results confirm that the ventilation systems are able to maintain the targeted performance levels in the OT operative life. However, they attest that significant differences in real OT contamination control capabilities do exist and could be ascribed to various design choices and to different operation and maintenance practices. The study shows and confirms that the air diffusion scheme and the design airflow rate are critical factors. Beside large variations in measurements, the performance values, in terms of control of airborne particle and microbial contamination (in air and on surfaces), for P-UDAF systems are better than those that were assessed for the MAF air diffusion solution. The average performances do increase with increasing airflows, and the results offer a better insight on this relationship leading to some possible optimization.

Influence of the Built Environment on Airflow, Contamination, and Infection in the Operating Room: A Systematic Literature Review

“…22,70,110,99,100,102,103,[106][107][108][109] Eight articles included microbial contamination in the operating room as one of the recorded outcomes, although the specific ventilation systems under study varied between articles. 22,70,99,[106][107][108][109][110] Similar to the literature on LAF, there was a general consensus that microbial contamination is lower in operating rooms equipped with unidirectional airflow as opposed to turbulent and mixed airflow systems, regardless of how this was measured (i.e., active versus passive sampling methods). Those studies that compared mixed and turbulent airflow systems found that the microbial contamination is often very similar, and any differences tend not to be statistically significant.…”

“…Of the 46 studies on OR ventilation that were based on empirical data, 22 did not investigate LAF. 7,22,[98][99][100][101][102][103][105][106][107][108]46,109,110,53,66,70,[94][95][96][97] It is important to note that the conflicting way in which authors use the term "unidirectional airflow" may have led to an underestimate of the number of papers that investigated LAF. Some authors equate unidirectional airflow with LAF and use these terms interchangeably, while others do not; some studies explicitly differentiate between the two.…”

“…Of the 22 non-LAF empirical studies, eleven articles compared two or more ventilation systems, most of which involved a comparison between turbulent or mixed ventilation and a unidirectional airflow system. 22,70,110,99,100,102,103,[106][107][108][109] Eight articles included microbial contamination in the operating room as one of the recorded outcomes, although the specific ventilation systems under study varied between articles. 22,70,99,[106][107][108][109][110] Similar to the literature on LAF, there was a general consensus that microbial contamination is lower in operating rooms equipped with unidirectional airflow as opposed to turbulent and mixed airflow systems, regardless of how this was measured (i.e., active versus passive sampling methods).…”

EPOS trial: the effect of air filtration through a plasma chamber on the incidence of surgical site infection in orthopaedic surgery: a study protocol of a randomised, double-blind, placebo-controlled trial

“…Lidwell et al carried on their work, showing that ultra-clean air (ie, <10 colony-forming units (CFUs)/m 3 ) in combination with body-exhaust suits and prophylactic antibiotics further improved infection rates 8–10. Based on their work, in combination with several reports showing that laminar air flow (LAF) reduces bacterial contamination in the OR air,11–13 many ORs are today equipped with LAF ventilation. Unfortunately, though, when evaluated in large cohort studies, systematic reviews and meta-analyses, LAF systems in modern state-of-the-art ORs have so far failed to prove efficient in preventing infections, compared with conventional ventilation 14–19…”

Current Status and Factors Associated with Clean Operating Rooms: A Survey of Hospitals in China

“…Relatively few studies have investigated compliance with air quality standards and management of ORs [17][18][19], and none, to the best of our knowledge, have identified factors associated with the management of air quality in clean ORs in China. erefore, the aim of this study was to survey the usage, maintenance, and testing of ventilation systems in clean ORs among hospitals in China with the use of an online questionnaire.…”