Respiratory care systems

Position: Research & Development Engineer at Medisize


For three years I was part of the R&D team of this manufacturer of medical products. We were specialised in anaesthesia and respiratory care solutions; in particular the filtration and humidification of breathing air for patients at operation theatres and intensive care.


The company had full cleanroom facilities to produce all sorts of plastic components and products in large numbers. We had a wide range of machinery, including injection moulding, thermoforming, ultrasonic welding and (semi to full automatic) assembly and packaging lines and a sterilisation chamber to our disposal.


Project organisation
Within our three-headed R&D team, each of us managed his own projects by leading multidisciplinary development teams, assembled from representatives of relevant departments, like quality & regulatory affairs, production, purchasing and marketing & sales. A project could include all design stages; from market research, problem analysis, financial forecasts and setting the goals and requirements, through idea generation, modelling and prototyping, process design, selection of materials and suppliers and ordering tools and equipment, to running trial batches, extensively testing and adapting until we got green light to start with production. 

Patient ventilated by machine

Conditioning and filtration
A patient under narcosis or in coma is not or insufficiently able to breath, and therefore has to be ventilated by a machine. The pressurised air that is used is too cold and dry and needs to be conditioned to avoid damage to the patients lungs. As the upper airways (naturally performing this function) are bypassed by an inserted tube, heat and moisture must be added to the inflowing air. 


This humidification can be done either actively, by means of an electronic boiler that provides steam, or passively, by 'catching' the patients heat and moisture from the exhaled air, and give it back to the inflowing stream. At Medisize we developed a range of products based on this latter principle, in the medical world known as HME's (Heat and Moisture Exchangers).


The breathing air must also be cleaned from bacteria and viruses. Therefore a microbiological filter is added to the system. The required levels of filtration efficiency are strictly prescribed by international regulation.


Filter-HME line for children
My first project was to extend a filter-HME line for babies and young children. I developed two alternatives of an existing product, which are still produced in large numbers.


High efficient mechanical filter
Additional to the existing microbiological filters, based on electrostatic filtration, I developed a mechanical filter that could reach a higher efficiency level. In close cooperation with a supplier we developed a package of pleated filtration paper with an optimal combination of high capacity, low air resistance and small volume ('dead space').


Parallel to the product design, we developed a production line to pleat and glue the paper in harmonica-shape and cut out the circular filters. For the housing a plastic injection moulded ring was designed, on which at both sides different ISO-connectors could be welded. To obtain an airtight connextion between filter package and plastic housing, we developed a spincast machine that could inject glue to the assembly while rotating it at high speed.


We also developed an inline efficiency test, consisting of a particle generator that blew aerosols with the size of the smallest microorganisms against the filter and a particle counter at the other side. The required efficiency for each product was 99,999%.


Other R&D tasks
Apart from these extensive projects I contributed to projects led by colleagues and examined new ideas. To stay close to practice and get new insights from the market, we maintained close contacts with anaesthetists and other hospital specialists, visited medical conferences, etc. We also gave technical support to the sales team. 



Breathing filter-HME for children

High-efficient microbiological filter