March 2020. Whether you take Bergamo or Stras­bourg as an example, in Spring, news about the coro­n­avirus pandemic suddenly made it very clear what can happen when a virus gets out of control, hospi­tals are over­whelmed and there’s not enough life-saving medical equip­ment. Employees from Viess­mann were also trou­bled when they heard about the dramatic situ­a­tion and wanted to act. The company from Allen­dorf in Northern Hesse began producing face masks and disin­fec­tants in the early stages of the pandemic. Then the staff came up with another idea: why not also produce respi­ra­tors? After all, a heating system also moves air.

The goal: a respi­rator that can be deployed quickly

Jan Heiner was pleased to accept the chal­lenge. He is normally respon­sible for fuel cell heating systems at Viess­mann. Starting in March, he led the “respi­rator” project, which he and 20 other employees were approved to work on. “Of course, we very enthu­si­astic and we got stuck into the work right away. But we were a bit skep­tical about whether it would actu­ally be possible.”

The advan­tage of Viess­mann heating appli­ances is that they are modular in design. This makes it easy to configure the design. (Photo: Viess­mann)

The goal was to have a ready-to-use device as quickly as possible that could save lives. To start with, Heiner contacted anes­thetists and inten­sive care doctors at the Luisen hospital in Aachen, an acad­emic teaching hospital at Aachen Univer­sity Hospital, to discuss the require­ments for this type of device: “The breathing curve is similar to a sine curve. There is an upper and lower pres­sure level.” For arti­fi­cial breathing, the device must first build up pres­sure to allow air to enter the lungs and then reduce pres­sure so that it can be breathed out. The doctors also pointed out that the oxygen admix­ture is also an impor­tant require­ment. “Depending on the course of illness, it’s neces­sary to supply patients with a higher oxygen concen­tra­tion,” Heiner explains.

Once he had quickly learned about lung func­tion, he believed that the task was possible. “The advan­tage is that our heaters have a modular design, so we have the flex­i­bility of replacing compo­nents or recon­fig­uring the struc­ture.” The chal­lenge was then to fulfill the special require­ments with existing compo­nents. “After all, we didn’t want to inter­fere with the medical equip­ment manu­fac­turers’ supply chains, which already had bottle­necks.”

The braking func­tion is the deciding factor

That’s what those respon­sible at ebm-papst thought as well when Viess­mann put in a request for a suit­able blower on March 30 in Land­shut. Markus Wein­gart, Head of the Elec­tronics Depart­ment, explains: “In St. Georgen, we already produce blowers for these types of appli­ca­tions, but they have to be reserved for medical equip­ment manu­fac­turers. So we had to look for an alter­na­tive that was avail­able right away.” They quickly decided to use an elec­tronic gas blower system that was already produced in high volumes for Viessmann’s condensing boilers. “In prin­ciple, the blower doesn’t care whether we mix natural gas and air or oxygen with air, only the gas blower’s very long service life is reduced by the higher oxygen content,” Wein­gart explains.

In prin­ciple, the blower doesn’t care whether we mix natural gas and air or oxygen with air.

Markus Wein­gart, Head of Depart­ment Elec­tronics, ebm-papst

Since a single system solu­tion with an inte­grated gas valve doesn’t build up the neces­sary pres­sure within seconds, the Viess­mann engi­neers decided to connect two blowers in series and take full advan­tage of the system limits. “Here, it was a great advan­tage that we knew exactly what the system limits were and didn’t have to take new measure­ments. We had it all on file. We usually train our prod­ucts very hard, so we know what’s possible mechan­i­cally and elec­tri­cally, and what the blower can handle,” says Wein­gart. Never­the­less, a crucial soft­ware adap­ta­tion was still neces­sary: a braking func­tion.

This is super­fluous in a heater, where the fan impeller simply ends when it is switched off. However, with a respi­rator, this would be fatal because it would not be possible to breathe out if air continues to flow into the lungs. There­fore, the pres­sure has to be reduced abruptly. “So, we repro­grammed the brake func­tion. The trick was to make it so that the brake current remains limited. If it’s too high, it could damage compo­nents. However, the avail­able hard­ware doesn’t allow this brake current to be measured, so we had to approach the problem purely theo­ret­i­cally,” says Wein­gart, describing the chal­lenge they faced.

The tension mounted: Was the unit suit­able for use in prac­tice?

The proto­types are ready and Viess­mann is prepared for series produc­tion of the respi­rator.

Just two weeks later, the adapted blower from Viess­mann was ready for instal­la­tion. In the mean­time, Heiner and his team adapted the housing, designed the connec­tions for oxygen and respi­ra­tory hoses and devel­oped their own air flow sensors. The crucial factor was whether the dynamics fit with the breathing cycle. As it happened, one of the pilots of the Viess­mann company jet was also a doctor. When he got wind of the project, he offered his support and provided a breathing dummy for carrying out tests. So far so good, but they hadn’t yet received a deci­sion from special­ists in Aachen, who had already received an initial proto­type. Heiner and his team were very tense: they had spent many week­ends and evenings working. But then came the crucial news: the unit was funda­men­tally suit­able! “We were all really proud, espe­cially as we ourselves were unsure whether we could do it,” says Heiner.

Ready for produc­tion for the next wave

Only eight weeks after the project began, Viess­mann deliv­ered initial proto­type devices to other coun­tries. At the same time, we decided to work together to prepare for mass produc­tion of these special blowers so that they would be ready in larger quan­ti­ties from the summer onwards. “The devices could also be used for mobile use, for example in exhi­bi­tion halls that are converted into emer­gency hospi­tals.”

But things turned out differ­ently: the measures taken to prevent the virus were very effec­tive. Luckily, there were already enough respi­ra­tors avail­able. “A certi­fied medical device was never our goal. But in the event of a crisis, we would have hoped for a special approval.” Heiner is also glad that the worst-case scenario has not happened so far. Despite this, it has got him thinking: “I’ve seen images from coun­tries where patients have been helped manu­ally with breathing in an oper­a­tion. Using our devices in these scenarios would have been much better for the patients.”