Environmental Monitoring in the OR to Reduce Surgical Site Infections

Surgical site infections (SSIs) are a significant cause of patient harm, prolonged hospital stays and increased healthcare costs. While SSI have multiple causes, environmental conditions within the operating room, including airborne particulates, room occupancy, door opening and temperature, may contribute to infection risk.

Environmental monitoring therefore offers an opportunity to improve understanding and management of operating-room conditions. Further clinical research is required to establish whether these interventions can directly reduce SSI rates.

Introduction

Surgical site infections (SSI) are among the most common healthcare-associated infections and can significantly affect patient recovery. In England, UKHSA surveillance data for 2024–2025 recorded 1,250 SSIs from 146,411 operations, with infection rates ranging from 0.4% for knee replacement to 8.3% for large bowel surgery [1].

SSI can have a devasting impact on patients, causing pain, prolonged hospital stays, additional surgery and, in severe cases, sepsis or death.

In addition to poor patient outcomes, SSIs increase healthcare costs through longer hospital admissions, antibiotics, wound care, diagnostic tests, readmissions and additional procedures. A study conducted in an English NHS hospital found that SSI resulted in 10 additional hospital days and an additional cost of £5,239 per patient [2]. Whereas a US study found that SSIs lead to a cost increase of $24,230 [3].

SSI are mainly caused by microorganisms entering the surgical wound. Common contributing factors include contamination during surgery, aseptic technique, poor skin preparation, inappropriate or delayed antibiotic prophylaxis and prolonged or complex surgery. Patient issues such as diabetes, obesity, smoking, poor nutrition, and weakened immunity are also known to be contributing factors.

This white paper focuses on how environmental factors in the operating room can influence rates of SSI.

Literature review

Airborne particulates

It has been demonstrated that airborne particulates are a transport mechanism for the microbes that can cause SSI. A landmark study [4] from 1983 surveyed operations for total joint replacement in 15 hospitals. The study found that 51 to as many as 539 bacteria-carrying particles per cubic metre were present in the operating rooms and there was a good correlation between the air contamination and the joint sepsis rate. There was also a correlation between the mean values of air contamination and the numbers of bacteria isolated from wound wash-out samples. The study concluded that by far the largest proportion of bacteria found in the wound after prosthesis insertion reached it by the airborne route.

Tan et al. [5] showed through experimental measurements that PM 5 and PM 10 show a noticeable correlation with microbial counts and suggested that particulate data can be used for general monitoring of microbial contamination in operating rooms.

A further study [6] in France was performed in 13 operating rooms performing cardiac and orthopaedic surgery in 10 health care facilities. For each surgical procedure, 3 microbiologic air counts, 3 particles counts of 0.3, 0.5, and 5 μm particles, and 1 bacteriologic sample of the wound before skin closure were performed. The study suggested that particle counting is a good surrogate of airborne microbiologic contamination in the operating room.

Door opening frequency

Operating rooms are typically at a positive pressure relative to surrounding areas to reduce the influx of contaminated air and the associated risk of surgical site infection. Sadrizadeh et al. [7] have shown through computational fluid dynamics that penetration of bacteria carrying particles from the corridors is reduced in positive-pressure operating rooms. However, frequent door opening would interfere with airflow ventilation systems, alter the pressure gradient and increase patient infection risk.

Room occupancy levels

A 2023 study [8] employed a retrospective review of 223 consecutive patients who underwent immediate implant-based reconstruction. Patient demographics, comorbidities, smoking status, laterality, number of personnel, use of drains and length of surgery were collected. The primary outcome assessed was surgical site infection with secondary outcomes of delayed wound healing, skin necrosis, hematoma, seroma and reoperation within 90 days. The study found that patients with SSI had undergone procedures with an average of 8.7 scrubbed individuals, whereas patients who did not suffer SSI had an average of 7.9 individuals scrubbed involved in their procedure. The authors concluded that an increased risk of SSI was associated with higher operating room occupancy.

A further study [9] in Sweden assessed the link between the number of people in the operating room and air contamination rate in the vicinity of surgical wounds during 30 orthopaedic procedures. The study found a weak, yet still positive correlation between the concentration of colony forming units (CFU/m3) and the number of people in the operating room.

Shaw et al. [10] used active sampling methods to assess microbial colony counts in 28 working operating rooms to determine the factors affecting air contamination. The study concluded that the number of personnel and their activities critically influenced the microbe concentration in the air.

Noise

A study in the UK [11] assessed whether noise levels in the operating room were associated with levels of SSI. Data was collected from hernia repairs where the patients were considered fit and at low risk for SSI. The study found that noise levels were substantially greater in procedures resulting in SSI from a time point of 50 minutes onwards, which correlated to when wound closure was occurring.

Temperature

It can be expected that bacteria in the operating room are not generally multiplying freely in the air, however, temperature and humidity may influence airborne microbial viability. A study at the University of Leeds [12] found that the concentration of airborne microbial measured as aerobic colony count (ACC) did correlate with temperature.

This review found very little research on a direct correlation between temperatures and airborne microbes within operating rooms. The exception was the earlier referenced Shaw et al. study [10] that identified air temperature as an independent factor that influenced bacterial counts in operating rooms.

New technology opportunities

The ability of medical equipment suppliers to address the requirements of environmental monitoring in the operating room has historically been limited. Particulate detection equipment has been installed on a limited number of occasions and has generally been prohibitively expensive. Temperature and humidity sensors have been fixed to operating room walls, well away from the patient and produce data that is not representative of conditions in the surgical field.

The Brandon Medical Quasar Qi surgical light presents a new opportunity to monitor environmental conditions directly in the surgical field. Sensors embedded in the light mean that particulate levels, temperature and humidity may be monitored directly above the patient.

The Quasar Qi sensor suite also includes carbon dioxide sensors. Carbon dioxide is monitored as a proxy measurement for room occupancy; more people equates to higher C02. The sensors used are based on recent technology developments and provide accurate performance in a cost-effective package.

This white paper has demonstrated the links between environmental conditions and SSI, but measurement of the data must lead to practical and actionable responses. The data measured by Quasar Qi is actionable on three levels of implementation:

Implementation level 1 – local display

The sensor outputs may be displayed locally on either a dedicated Qi Surgical Light Control or a Theatre Control Panel (iTCP). The sensors can be configured with thresholds so that local alerts are communicated to the surgical team. These alerts may be accompanied by simple text-based guidance such as “increase ventilation” or “reduce room occupancy where possible”.

Implementation level 2 – automated response

Making the sensor data available to the theatre control panel presents a valuable opportunity for automated responses. The theatre control panel will typically have existing communication links with the operating room ventilation systems, including ultra clean laminar flow and turbulent systems. This connectivity may be exploited to establish automated control loops, so that a high particulate or carbon dioxide measurement can automatically lead to an increase in ventilation. This approach not only gives the surgical team confidence that the environmental factors are being monitored, but that appropriate responses are being taken that do not need their intervention.

Implementation level 3 – big data analysis

Once the sensor data is accessed by the theatre control panel it can be made available to the hospital network. This then presents the hospital with the opportunity to correlate the environmental conditions during surgery with patient SSI outcomes. Artificial intelligence systems can then be employed to look for trends that provide insights that can improve procedures and lead to reductions in SSI. For example, can the maximum numbers of students be established for each procedure type so that SSI risk is minimised? Or could the operation of the ventilation levels and run times be optimised to have maximum impact on SSI, whilst also having confidence about when it can go into set back and minimise energy use.

Conclusion

Surgical site infections remain a significant challenge for healthcare providers, with substantial consequences for patients and healthcare systems. While SSI have multiple causes, the evidence reviewed in this white paper demonstrates that environmental conditions within the operating room—including airborne particulates, door opening frequency, room occupancy, noise and temperature —can influence the risk of SSI.

The evidence presented therefore supports the development of environmental monitoring as an important component of a broader SSI prevention strategy. Quasar Qi provides a platform through which environmental conditions can be measured closer to the surgical field and, importantly, transformed from passive measurements into actionable information. Further clinical validation and outcome-based research will be required to determine the extent to which this approach can translate into measurable reductions in SSI, but the combination of real-time monitoring, automated response and data-driven analysis presents a promising opportunity for reducing the risk of surgical site infections.