Flow meters for quality control of respiratory products

March 27, 2020 Johan van 't Leven

In 2018 I visited a company that is specialized in the development and design of reliable healthcare solutions.  At that time I talked to both Directors Ivar Donker and Henk van Middendorp about the activities of Relitech in the medical industry and their Metabolic Simulator. They showed me the purpose of flow meters in their process.

cardiopulmonary exercise test
Cardiopulmonary exercise test

Metabolic simulator: quality control for respiratory products

There are many respiratory products used in the world, for example spirometry and ergospirometry devices. To assure they are performing well and to meet the demands of customers and legal regulations, they need to be validated. Currently, the quality control is limited by calibration of each sensor (O2, CO2 and flow) separately, but the critical dynamic interaction between the sensors is not included. Therefore, Relitech developed for their customers in the field of respiratory products a new metabolic simulator. 

With theMetabolic Simulator, you can go to the device that needs to be tested. At the test site, the device mixes two pure gases, N2 and CO2 and generates real time breathing patterns. Because of the smart design, various human breath patterns can be precisely simulated, resulting in capnographs closely resembling the ones of test subjects. 

Thermal mass flow controller

The simulator mixes pure nitrogen and carbon dioxide by using two Bronkhorst thermal mass flow controllers. By mixing those two gases you can generate breathing gas exchange patterns, real-time and extremely close to authentic human breathing patterns. The results are so-called capnographs that resemble the ones of a patient. On the readout display of the Metabolic Simulator the capnograph values are visible. V’CO2 represents the exhaled amount of carbon dioxide and V’O2 is the amount of oxygen inhaled. BF is simply an abbreviation for breathing frequency.


Relitech metabolic simulator

“Using mass flow controllers is not new to me…” Van Middendorp explains, “…as I was already involved in designing lung function systems long before I joined Relitech in 2002.”

“As we started developing the metabolic simulator here at Relitech, we were looking for compact and highly accurate mass flow controllers and that’s where Bronkhorst and I crossed paths. So partly by using these compact thermal flow controllers we were able to develop an even more compact simulator design.”


Directors Relitech
Directors Ivar Donker and Henk van Middendorp from Relitech

Relitech, reliable technology

With dedication and passion Relitech develops reliable technology by focusing on electronics, software and embedded software. In combination with consultancy regarding measurement technology, their core competence lies within the medical sector, such as lung function measurement, anaesthesia and hyperthermia applications. For this, the company is ISO13485 certified. By working closely with various universities and academical institutes, multinationals and small businesses they have built an impressive and very diverse customer portfolio.

The role of Bronkhorst

With our own expertise in precise and reliable mass flow meters and controllers for liquids and gases, we work closely together with companies  in the high tech industry and with technical universities to develop solutions helping you to optimise your flow process.  
Feel free to contact us  if we can assist you. 

  • Check out the application story of quality control for respiratory products.
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