Scientists measure oxygen flows and concentrations that the equipment is able to provide to patients at different respiratory rates

The battle against Covid-19 involves a number of researchers, teams, and laboratories throughout the country, but not even the Coordinator of the Advanced Combustion Diagnostics Laboratory of the FAPESP Shell Research Centre for Gas Innovation (RCGI), Professor Guenther Carlos Krieger Filho, had imagined that the laboratory could also join this cause. Last Sunday, April 12, the laboratory that had been set up to analyze combustion reactions via laser techniques was used by one of his colleagues – Professor Raul González Lima, specialist in Biomedical Engineering at Poli – to test the Inspire, the name given to the emergency ventilator created by González and his team from the Polytechnic School of the University of São Paulo (Poli-USP), which has been a focus of attention of the media in recent weeks.

The team developed a ventilator that can be produced in up to two hours and is much cheaper than the devices now available on the market (which cost an average of R$15,000, while the Inspire model costs only R$ 1,000). “My colleague and also Poli Professor, Raul González, needed to test his prototype, in order to determine the oxygen flows and concentrations that the equipment is able to provide to patients, at the different rates that simulate the breathing process of the human lung. At the laboratory, we have a gas analyzer and a gas flow meter, so we offered to help, since the Professor needed to quickly perform these tests,” Krieger explained.

Therefore, the two Professors used the O2, N2, and CO2 gas lines, as well as the meters and gas analyzers of the laboratory to design a test that would be able to indicate the O2 content delivered by the ventilators. According to Krieger, since the laboratory’s meters are designed for analyzing the combustion processes in vehicle motors and industrial burners, it was necessary to make creative adaptations of the laboratory for testing the Inspire within the extremely short deadline demanded by the task.

“For example: our gas meter only measures the oxygen present in a gaseous mixture of up to 31%. But, in this case, we needed to know the maximum O2 that the ventilator would be able to deliver to the patient. We knew that it needed to be more than 31%, so we added CO2 or N2 in the place of O2. As we added these, we knew, proportionally, how much O2 was being delivered,” he revealed.

According to him, that procedure is not appropriate for an analysis certifying the equipment, but it was useful for the team in charge of developing the ventilator to make a laboratory estimate of the O2 content of the gas mixtures that go from the device to the patient. The team is looking for equipment that can deliver something close to 100% oxygen.

“The most important thing, at the end of the day, is that we were helpful in providing a measurement that proved to be very close to the theoretical estimates that Raul had made for the equipment. If we had a device that was able to measure the O2 content of up to 100%, it would be perfect. But we didn’t have that, and time was short. So, we did some creative improvisation.”

Respiratory rate – The tests included simulating a receptacle for connecting the outflow of the ventilator to the gas analyzer. Here, creativity also played a positive role. “We used a party balloon. The tip of the oxygen flow meter had about the diameter of a pencil, and it fit into the neck of the balloon. At the bottom of the balloon, we made another hole, where we increased the volume of the balloon, filling it with air. In this case, the objective was to measure the respiratory rate of the patient, in order to allow synchronizing the supply of O2 of the device with that respiratory rate. We tested various rates, because we had control of these variables: pressure, flow…”

According to the Professor, in the race against time during this pandemic, the most important thing is to be able to provide real and timely help. “Raul was in a hurry and we were there to help him. In this case, he would probably not have had the luxury of waiting for an ideal testing situation in another laboratory, ideal in the sense of being more adapted to his project. We were very happy to be able to help. This is a valuable contribution by the RCGI during the difficult times we are experiencing.”

The ventilator developed by the researchers, under the guidance of Raul González, was registered with an open source license, which allows anyone or any company to access the manufacturing protocol and build it, merely by obtaining the authorization of the National Sanitary Surveillance Agency (ANVISA). For more information regarding this license, click here.