As a preparation for the final tests in Congo, several full-scale pilot tests were carried out in September 2024 at Kungälv’s hospital north of Gothenburg, Sweden.
To imitate an operating room in a simple environment, a staff room in a section for surgical emergency care was used. The section was newly built and not yet in use.
Particle meters with the possibility of studying time courses in real-time and over longer periods were used. Similarly, bacterial levels in the air were studied with traditional agar plates (soy-based growth medium) and microbiological sampling during continuous real-time measurements.
The tests were carried out under surgery-like forms regarding the number of people, movements (activity), clothing, room size and furniture. Three cases of clothing sets were tested:
- Cotton clothes + simple hood + mouth guard + sandals
- Disposable clothing + full hood + mouth guard + sandals
- As 2) but covering plastic bags over the sandals. The bags were taped to the shins.
By alternately having the air cleaner and supply air fan in the OFF and ON positions, respectively, their impact on the air quality (particles and bacteria) was tested.
Results
The results from the tests in Kungälv’s hospital were promising. The air cleaners reduced the particle content by approx. 10 – 70 times, depending on the particle diameter, the bacteria content dropped by approx. 10 – 15 times (se diagram below). The results also clearly showed the importance of surgical clothing for the level of airborne bacteria in the room. Logically, further improvement was demonstrated when the feet were covered with plastic bags (Case 3 above).
The Room
Dimensions: 5.75 x 7.1 x 2.6 m. Area = 41 m2. Volume = 106 m3
The room was prepared as follows:
- 4 active air cleaners. Total clean air flow (CADR): approx. 3,500 m3/h. A further 4 air cleaners were installed to investigate the sound levels and air drafts in case of larger installations. But during the operation tests, their filtering was OFF. The air cleaners were hung on wooden stands (to avoid damage to the new wall surface) in the connection between wall/ceiling.
- 1 dehumidifier was placed on the floor
- 1 supply air fan was mounted outside the room, behind a sealing wooden board in the doorway. The air was supplied through a hole in the wooden board.
- 1 operating table (dining table with a cotton cloth)
- 1 horizontal ventilation duct with circular cross-section, heated to body temperature was placed on the operating table to simulate a patient
- 3 small tables were placed next to the operating table
Smoke Visualization
Before the surgical tests, smoke visualization was done to characterize the air movements in the room. We were able to establish that the location of the air cleaners only has a minor impact. Since operating lights are normally ceiling-mounted, movable and take up a lot of space above the patient table, it is difficult to retrofit laminar flow ventilation (UDF) above patient tables. Therefore, the option of hanging the air cleaners from the ceiling was not tested, but technically, it would work just as well.
Clothes
Operating room clothing has a major impact on the level of airborne bacteria. In low-income countries, cotton textile clothing is often used, worn by long use, many washings and sterilizations, which gives a high permeability of bacteria. Disposable clothing used by surgical personnel in Sweden is often too expensive to use routinely in low-income countries. “Boots” can complement well-functioning clothing to capture bacterial fallout from the staff and prevent further spread of airborne microorganisms from the staff to the room.
Continuation
In late autumn 2024, installation, introduction and testing of the concept is planned in the two hospitals in Bukavu (DR Congo). Then, the air cleaner capacity will be roughly doubled compared to the tests in Kungälv. In actual operating theatres with ongoing operations of various kinds, particle and bacteria levels will be measured, with registration of the number of people and events such as door
More information to come…!