Orthopaedic surgery
Monitoring air quality during joint replacement
Despite the well-documented relationship between microbiological air quality and deep infection rates in joint replacement surgery, routine monitoring of operating theatres during use is still not standard practice. Wan Li Low provides an insight into a pilot study and national audit on air quality in operating theatres, and considers the best approach to drive improvement.
Surgical site infections (SSIs), pose a significant challenge in healthcare, leading to substantial patient morbidity and increased healthcare costs. They account for approximately 16% of all hospital associated infections, and often result in extended hospital stays, pain, and prolonged or permanent disability.1,2
Specifically, SSIs can
double the length of postoperative hospital stays, and greatly elevate care costs,3,4 due to the association with additional surgical procedures, treatment in intensive care units, and higher mortality rates.5 In 2021, the National Joint Registry documented a significant number of revision procedures, arthrodesis and amputations due to infected hip and knee replacements.6
patients with these SSIs cannot be cured and require treatment with long-term antibiotics. Such infections not only incur a tremendous cost in human suffering, but also impose a substantial financial burden on the NHS.
The link between infection rates and the Some
microbiological quality of operating theatre air is well established, particularly in orthopaedic surgery. This relationship was first suggested by Charnley’s investigations in 1972 and later confirmed by the Medical Research Council trial of ultra clean air (UCA).7,8 Despite the well-documented relationship between microbiological air quality and deep infection rates in joint replacement surgery, routine monitoring of operating theatres during use is still not standard practice. Guidance for the design, performance and testing of operating theatres in the UK is provided by the Health Technical Memorandum (HTM) 03–01.9 These guidelines include annual engineering checks. However, they do not specify regular microbiological testing of theatres, either when empty or in use. This lack of air quality testing contrasts sharply with pharmaceutical production facilities, where microbiological
air sampling is conducted during the manufacturing of each batch of product. The pharmaceutical industry uses millions of settle plates annually to test production facilities, yet the NHS has not implemented their routine use during surgery, despite the severe consequences of deep infections in joint replacements.
Conventional air quality testing Ensuring optimal air quality during surgical procedures is crucial for minimising the risk of SSIs. Even when the engineering aspects of the facility meet regulations, the microbiological conditions can still be compromised due to various factors. These include the number of personnel in the surgical team, their attire and behaviours, the specific setup within the operating theatre, and the effectiveness of any ultraclean zones implemented. Historically, monitoring air quality in operating
theatres has relied on volumetric counting methods, primarily using slit samplers or membrane-based samplers. These methods are effective but have key drawbacks. Volumetric sampling requires trained microbiology staff to be present in the operating theatre for extended durations, rendering them impractical for routine audits due to labour intensity and logistical challenges. Alternatively, passive sampling using settle
Fig 1. Traditional slit samplers used to test air quality in an operating theatre
plates, also known as Petri dishes, has been proposed as a simpler and potentially more practical method for monitoring microbiological air quality in operating theatres. In this method, settle plates are exposed in the theatre environment for a specified duration, and then incubated, to promote potential microbial colony growth. Any resulting colonies are counted and used to measure the air microbiological contamination. The microbial deposition rate (MDR) is calculated from the plate area and the exposure time, reporting the number of
October 2024 I
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