Ultraclean air systems and the claim that laminar airflow systems fail to prevent deep infections after total joint arthroplasty

Effect of unidirectional airflow ventilation on surgical site infection in cardiac surgery: environmental impact as a factor in the choice for turbulent mixed air flow

BACKGROUND

Surgical site infection (SSI) in the form of postoperative deep sternal wound infection (DSWI) after cardiac surgery is a rare, but potentially fatal, complication. In addressing this, the focus is on preventive measures, as most risk factors for SSI are not controllable. Therefore, operating rooms are equipped with heating, ventilation and air conditioning (HVAC) systems to prevent airborne contamination of the wound, either through turbulent mixed air flow (TMA) or unidirectional air flow (UDAF).

AIM

To investigate if the risk for SSI after cardiac surgery was decreased after changing from TMA to UDAF.

METHODS

This observational retrospective single-centre cohort study collected data from 1288 patients who underwent open heart surgery over 2 years. During the two study periods, institutional SSI preventive measures remained the same, with the exception of the type of HVAC system that was used.

FINDINGS

Using multi-variable logistic regression analysis that considered confounding factors (diabetes, obesity, duration of surgery, and re-operation), the hypothesis that TMA is an independent risk factor for SSI was rejected (odds ratio 0.9, 95% confidence interval 0.4-1.8; P>0.05). It was not possible to demonstrate the preventive effect of UDAF on the incidence of SSI in patients undergoing open heart surgery when compared with TMA.

CONCLUSION

Based on these results, the use of UDAF in open heart surgery should be weighed against its low cost-effectiveness and negative environmental impact due to high electricity consumption. Reducing energy overuse by utilizing TMA for cardiac surgery can diminish the carbon footprint of operating rooms, and their contribution to climate-related health hazards.

Clinical Issues - July 2023

Use of clean versus sterile pneumatic tourniquet cuffs Key words: clean, sterile, pneumatic tourniquet, incision site, cuff placement. Active shooter crisis preparedness Key words: active shooter preparedness, emergency response, active shooter event, evacuate, barricade. Heating, ventilation, and air-conditioning parameters Key words: laminar airflow (LAF); unidirectional ultraclean air-delivery system; unidirectional downward airflow; turbulent; heating, ventilation, and air-conditioning (HVAC) system. Modifying directional air pressure settings Key words: directional air pressure, negative-pressure room, positive-pressure room, bronchoscopy, parameters.

Infection prevention and control considerations regarding ventilation in acute hospitals

Infection prevention and control team members (IPCTM) are often intimidated by aspects of ventilation as they relate to healthcare, because they consider them technical and outside their area of comfort and expertise. However, engineers, estates departments and planners need IPCTM input to ensure appropriate design and use. The main areas of importance centre on the operating theatre, the provision of air-controlled ventilated isolation rooms, and how to respond to major outbreaks/pandemics. Concentrating on basic principles of infection prevention and control, developing relationships with key departments and individuals, and applying best practice to these and other areas as they arise, are of great value. Some background, information and suggestions are provided for IPCTM with a view to providing simple practical advice in these areas.

Influence of surgical team activity on airborne bacterial distribution in the operating room with a mixing ventilation system: a case study at St. Olavs Hospital

BACKGROUND

Operating rooms (ORs) have strict requirements regarding cleanliness. While existing standards concerning the ventilation and staff guidelines are theoretically sufficient to subvert the threats posed by micro-organisms within the room, there exist potential sources of contamination due to human activity around the area. Studies exploring this influence of human activity on distribution of micro-organism contamination in ORs have relied on manual observations, or indirect methods such as number of door openings.

AIM

To utilize depth registration sensing technology to identify the activities of surgical staff and investigate their effect on the distribution of airborne micro-organism contamination in ORs.

METHODS

A mock surgical experiment was performed using a depth registration technique for the dynamic capturing of human presence and activity levels. Field measurements were carried out in one real OR to analyse its influence on the bacterial distribution in ORs with mixing ventilation system.

FINDINGS

Bacterial contamination levels tended to correlate with higher activity levels, albeit with some inconsistencies. The highest activity levels were around the surgical bed when the patient was placed, and around the instrument table during the surgical procedure. Locations with obstructions had the highest cfu densities, indicating that airflow patterns are important in such spaces.

CONCLUSION

Our activity monitoring methods demonstrate a novel means of studying the influences of human activities in hospital rooms.

Laminar airflow decreases microbial air contamination compared with turbulent ventilated operating theatres during live total joint arthroplasty: a nationwide survey

BACKGROUND

Preventing surgical site infections and prosthetic joint infections is crucial for patient safety after total joint arthroplasty. Microbial air contamination has been suggested as a risk factor. Therefore, the ventilation system that will reduce air contamination most effectively in operating theatres (OTs) has been discussed.

AIM

To determine whether laminar airflow (LAF) ventilation is superior to turbulent airflow (TAF) ventilation by looking at the colony forming units (cfu) count during live total hip and knee arthroplasties. Furthermore, to explore whether the number of OT personnel, door and cabinet lock openings and technical parameters of the ventilation systems have an impact on the number of cfu.

METHODS

Active air sampling and passive sedimented bacterial load were performed in 17 OTs, equipped with either LAF or TAF ventilation, during 51 live surgeries while observations were noted.

FINDINGS

LAF OTs reduced cfu counts compared with TAF OTs during live surgery (P<0.001). All LAF OTs provided ultraclean air whereas TAF had nine procedures exceeding the threshold of 10 cfu/m³. Door and cabinet lock openings and number of personnel did not influence the cfu count, while it decreased with increasing volume and total air change per hour (P<0.05).

CONCLUSION

All LAF OTs had cfu counts within recommendations and provided lower cfu counts compared with TAF OTs. The number of OT personnel and total openings did not have an influence on cfu counts. Increased volume of the OT and total air change per hour showed a decrease in active cfu counts.

Ventilation design conditions associated with airborne bacteria levels within the wound area during surgical procedures: a systematic review

BACKGROUND

Without confirmation of the ventilation design conditions (typology and airflow rate), the common practice of identifying unidirectional airflow (UDAF) systems as equivalent to ultra-clean air ventilation systems may be misleading, but also any claims about the ineffectiveness of UDAF systems should be doubted. The aim of this review was to assess and compare ventilation system design conditions for which ultra-clean air (mean <10 cfu/m³) within 50 cm from the wound has been reported. Six medical databases were systematically searched to identify and select studies reporting intraoperative airborne levels expressed as cfu/m³ close to the wound site, and ventilation system design conditions. Available data on confounding factors such as the number of persons present in the operating room, number of door openings, and clothing material were also included. Predictors for achieving mean airborne bacteria levels within <10 cfu/m³ were identified using a penalized multivariate logistic regression model. Twelve studies met the eligibility criteria and were included for analysis. UDAF systems considered had significantly higher air volume flows compared with turbulent ventilation (TV) systems considered. Ultra-clean environments were reported in all UDAF-ventilated (N = 7) rooms compared with four of 11 operating rooms equipped with TV. On multivariate analysis, the total number of air exchange rates (P=0.019; odds ratio (OR) 95% confidence interval (CI): 0.66-0.96) and type of clothing material (P=0.031; OR 95% CI: 0.01-0.71) were significantly associated with achieving mean levels of airborne bacteria <10 cfu/m³. High-volume UDAF systems complying with DIN 1946-4:2008 standards for the airflow rate and ceiling diffuser size unconditionally achieve ultra-clean air close to the wound site. In conclusion, the studied articles demonstrate that high-volume UDAF systems perform as ultra-clean air systems and are superior to TV systems in reducing airborne bacteria levels close to the wound site.

The Influence of Surgical Staff Behavior on Air Quality in a Conventionally Ventilated Operating Theatre during a Simulated Arthroplasty: A Case Study at the University Hospital of Parma

Surgical staff behavior in operating theatres is one of the factors associated with indoor air quality and surgical site infection risk. The aim of this study was to apply an approach including microbiological, particle, and microclimate parameters during two simulated surgical hip arthroplasties to evaluate the influence of staff behavior on indoor air quality. During the first hip arthroplasty, the surgical team behaved correctly, but in the second operation, behavioral recommendations were not respected. Microbiological contamination was evaluated by active and passive methods. The air velocity, humidity, temperature, and CO2 concentration were also monitored. The highest levels of microbial and particle contamination, as well as the highest variation in the microclimate parameter, were recorded during the surgical operation where the surgical team behaved "incorrectly". Turbulent air flow ventilation systems appeared more efficient than in the past and very low air microbial contamination was reached when behavior was correct. Therefore, adherence to behavioral recommendations in operating theatres is essential to not undermine the effectiveness of the heating, ventilation, and air conditioning systems and employed resources.