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May 05, 2021

Stress-testing Temperature-controlled Air Flow ventilation

In recent studies researchers have come to the conclusion that conventional operating room ventilation does not deliver on the promise to reduce infections. One of the chief limitations is the amount of airborne bacteria that remains in working operating rooms that utilize these systems. So, what are the options, besides ultra-tight clothing, limiting staff numbers and restricting movements and behavior?


Kathy WaryeCEO at Infection Prevention Partners took the opportunity to ask Remko NoorMSc. Chief Technology Officer at Maximuse B.V. about his experience with Temperature-controlled Air Flow (TcAF) technology inside operating theaters.

Please tell us about yourself and your background?

I am Remko Noor. I have studied applied physics and integrated design in a construction environment. I am a senior consultant and senior project manager in healthcare projects. I am responsible for the development and organization of projects in hospitals within an established framework of a project such as quality, safety, risk, investments, sustainability, time schedule and organization. Together with a team I support and guide the hospital in complex innovations and construction projects.

In my profession I am an expert on Contamination Control. I am involved in and an advocate for innovations and developments in operating theatres, isolation units, central sterilization departments, intensive care units and imaging departments. The aim of my method is to create an optimal result for the patient and medical staff with a minimum of risk and maximum of comfort. I don’t look only at proven technology. I’m always searching for new opportunities from different aspects and fields.

R.J.R Noor

My knowledge and expertise have taken me to different places around the world. I was involved in projects in countries such as The Netherlands, China, Mongolia, Belgium, Slovakia, Egypt, the Caribbean, Portugal and Turkey.

In addition to my profession, I am board member of the Dutch Society of Contamination Control in the Netherlands. The society participates in development of both national and international standards, such as the NEN(Dutch standard) and ISO. We also share knowledge, by organizing courses and symposia. I am head of the committee which is responsible for the symposia and I am member of the expert panel for cleanliness of Surgical and Central Sterile Services Departments.

You were involved in a large new hospital contruction project at the Medical Center Leeuwarden (MCL) involving several new ORs. Please tell us about it.

The MCL is a general hospital in the province of Friesland in the Netherlands.The hospital employees 2,410 people.The hospital has 647 beds and 29,000 in-patient and 151,000 outpatient visits per year. It is a general hospital with all kinds of treatments. In total, 230 specialists treat patients. 

The hospital has 14 ORs with one preparation room for every two ORs. In the future, the hospital will have 2 ORs with separate preparation rooms. In the new project two hybrid ORs and 10 standard ORs will be built. 

 For the MCL project I was involved as expert in the field of OR ventilation. Because of my experience with different OR ventilation systems the hospital asked me to participate. They wanted to know the differences between ventilation systems and the pros and cons of each. In the Netherlands there are a limited number of people who are experts in different types of OR ventilation. During the past decade most people specialized in LAF plenum techniques and didn’t look to the developments in the market. I was involved in the first installation of a Temperature-controlled Air Flow (TcAF) system on the Dutch market, so they knew I had experience with the TcAF system.

During the search for the most optimal system we decided to do measurements – including a chaotic stress test – in a real OR in Gothenburg, Sweden, that uses TcAF.

The Netherlands has a new standard for operating room air quality that limits airborne bioburden based on the type of surgery. This is measured as the number of Colony Forming Units per cubic meter of air (CFU/m3). This is different from the standard in the US which specifies certain engineering controls like ACH, but does not place limits on CFUs.  Please describe the Dutch standard and what it requires. Why is addressing the actual airborne bioburden in operating rooms important? 

 It is most important to provide a clean environment for surgery where surgical site infections (SSI) are minimized or eliminated. To create a clean environment several aspects are important, including cleaning, behavior, discipline, hygiene and of course air handling. Measuring CFUs during surgery is important since it shows that the ventilation system and all other parts of the surgical process work together when it matters the most, .i.e. when the wound is open.

Classification measurement at Sint Maartenskliniek, Nijmegen, The Netherlands

 In 2014, a new guideline for OR ventilation was published in the Netherlands. This guideline is for the most infection sensitive surgery. Basically the guideline lists requirements for the OR itself.  It is important to know that classification of ORs in the Netherlands is based on measurements with particles at rest. We have four different classifications of ORs. Class 1 is for the most infection sensitive surgery. Within class 1 ORs we have a level 1 and a level 2. In class 1, level 1 a UDF system is required for orthopedic surgery and other surgery where prosthesis are used. Class 1 level 2 and other classes can have mixed ventilation. The medical specialists decide which class OR is necessary for the surgery.

The guideline doesn’t specify technical details for the ventilation system. We have no requirements for the amount of air or the minimum flow you need for the surgical area. We have a despcription of different ventilation principles which can be used and what functions they must fulfill. In this way new ventilation principles can be introduced in hospitals without being limited by the guideline. Unfortunally the guideline also includes a measurement method for classification which is based on a LAF system in an OR. This means that for other systems a new measurement method needed to be written. 

How did you learn about Temperature-controlled Air Flow?  Why were you interested in this technology?  

As an engineer and project manager I go to seminars, symposia and conventions. During those events I always look for new possibilities and perhaps other perspectives for existing products. At one event I found a supplier of TcAF systems and asked him for more information. After that I searched on the internet for more information and I got in contact with the manufacturer, Avidicare, which could tell me much more about the system because it was already common practice in Sweden. I was interested in this technology because it creates more free working space in an OR without extra risk for surgical site infections. And the system functions with less air which means a little less energy and a lower carbon footprint per OR.

Why did you feel it was important to stress test the system yourself? Please describe the test and measurement process.  

 At the time, the TcAF system was not known to many in the Netherlands while in Sweden a lot of TCAF systems were used and they were meeting the Swedish standard. The Swedish standard limits CFUs in working ORs based on the type of surgery. In the Netherlands we had no experience with TcAF, but wanted to open up for systems other than standard LAF and mixing ventilation. The hospital wanted to have the best system available on the market at the moment. To evaluate the system, it was necessary to do several tests with it in use. During those tests we did CFU measurements and particle measurements to see what happens during simulated surgery. 

 We did four different types of simulated surgeries. We started with surgery with a minimum number of people and equipment in the OR. During that procedure, doors stayed closed and the team did the procedure while we did the CFU measurement according to the Swedish standard. The final surgery was a trauma surgery where 13 people were running in and out of the OR to get equipment such as imaging equipment. During the surgery the door stayed open for several minutes and it was chaos inside the OR around the medical team who did the surgery. This was to really test an extreme situation and see how TcAF behaved.

We did two other surgeries, between the extremes, with an intermediate number of people and equipment. 

To get a total impression of the OR with the TcAF system we did 7 measurements during the day.

1.     We started with particle measurements At Rest to get an idea of the current situation inside the OR. 

2.     We simulated a knee procedure. During surgery 5 persons and the patient were present.

3.     We simulated an abdominal surgery. During surgery 7 persons and the patient were present.

4.     We simulated a cesarean section. During surgery 9 persons were present.

5.     We simulated a trauma at a leg. During surgery 13 persons were present, imaging equipment was added during surgery and the airlock function was ignored several times.

6.     We did the same particle measurements as we started with, At Rest.

We measured the recovery time of the OR according to the Dutch measurement method.

 During every surgery we did CFU measurements according to the Swedish standard and particle measurements at those positions as well. We added 3 extra particle counters in the periphery to see the effect of all movements inside the OR. 

How did the TcAF system perform overall?   

All results were very good. All CFU measurements met the Swedish standard of below 10 CFU/m3. The particles were always below 20,000 particles with a size 0.5 µm and 3,000 with a size of 5.0 µm. Even during the last chaotic surgery – the stress test – the level of particles was low compared to the activities we did in the OR and CFU levels were low as well. Since then we have seen many TcAF installations in the Netherlands.


Learn more about Temperature-controlled Air Flow technology

Avidicare developed the Opragon with the goal of creating a more effective, robust and energy efficient ventilation alternative for the modern operating room.  By combining HEPA filtered air with a temperature gradient, the Opragon maintains ultraclean conditions throughout the entire space. The technology more effectively reduces airborne contamination and, at the same time, creates a more comfortable and flexible working environment. 

About Maximuse

The Maximuse Integratio Operating Room, is a total concept designed to minimize risk of adverse events during and after surgery. The design guarantees patient safety and includes hygiene materials, the highest quality of air in the entire OR and a fully integrated IT platform. Careful consideration has been taken to both sound and lighting for maximum staff comfort. The innovative design is based on smart application of proven technology and produced after inputs from OR staff. Safety by design.

For commercial enquiries, please contact Avidicare.