Virginia Tech engineers and Carilion Clinic physician upgrade breathing support device into makeshift ventilator
April 17, 2020
As more Americans contract COVID-19, medical resources nationwide are stretched thin. Though hospitals must adhere to strict regulations concerning medical devices, in a dire situation, the innovation of engineers and clinician scientists could provide the kind of lifesaving devices needed to help patients.
To address potential ventilator shortages, mechanical engineers at Virginia Tech have partnered with a Carilion Clinic physician to upgrade bilevel positive airway pressure (BiPAP) machines, commonly used for treating sleep apnea, into makeshift ventilators.
“Carilion Clinic has gone to great lengths to prepare for a surge of Coronavirus patients. Right now, ventilators are well in hand, but we know that proactively preparing for the worst-case scenario, while hoping for the best, is the smartest move we can make,” said Edmundo Rubio, Carilion’s chief of pulmonology and critical care medicine, and a professor of medicine at the Virginia Tech Carilion School of Medicine. “If at some point we run out of ventilators, we now have a back-up option, thanks to our collaboration with Virginia Tech.”
Used to help patients with sleep apnea, BiPAPs maintain positive airway pressure to improve lung ventilation and oxygenation during sleep. One concern when using them to treat patients with contagious viral diseases, however, is that the machine could disperse virus-laden aerosols with each breathing cycle. Many of these systems also lack a back-up breathing rate, which could be necessary for sedated patients or those taking medications that reduce their ability to generate spontaneous breaths.
But Rubio thought that with a few upgrades to curb contamination and monitor air flow, a specific model of BiPAP that provides a back-up breathing rate, called a BiPAP S/T, could come in handy if ventilators become scarce.
As positive test results began rising in Virginia, Rubio pitched the concept to Michael Friedlander, Virginia Tech’s vice president for health sciences and technology, who connected him with Christopher Williams, a professor in the College of Engineering and interim director of the Macromolecules Innovation Institute.
Rubio gathered the tubing and filtration materials needed to prevent viral spread. But to make the machine perform more ventilator functions, he needed a way to monitor inflation and exhalation pressure and volume levels in real-time.
“Unlike normal ventilators, these machines don’t have sophisticated controls and monitoring capabilities,” Williams said. “We needed to find a way to help doctors measure air flow so they can calibrate safe settings based on individual patient scenarios.”
Williams brought in Joseph Meadows, an assistant professor of mechanical engineering, to lead project design and create a device to measure flow rates.
Meadows, an expert in fluid-thermal sciences, specializes in combustion for propulsion and energy production. Before he started this project, he was developing a facility to investigate supersonic jet noise. With his expertise, industrial experience, and familiarity with flow meters, Meadows was the right engineer for the job.
Within two weeks of meeting with Rubio, his team had evaluated four sensor designs, including two commercially available devices and two developed in-house. During the design phase, the engineers needed to consider multiple variables. Standard BiPAPs regulate air pressure, cycling between higher pressure during inhalation and lower pressure during exhalation to support the patient’s natural breathing rhythm. To calculate air volume, the engineers calibrated the sensor to track air flow in both directions, measuring each breath in and out. Before developing a prototype, the engineers compared each sensor’s pressure loss, accuracy, and material cost.
The measurements needed to be just right.
Patients with respiratory issues benefit from the BiPAP’s constant flow of positive pressure. On a microscopic scale, this pressure inflates the lungs’ air sacs called alveoli and prevents collapse. But if too much pressure is delivered, these alveoli can rupture, causing acute lung injury. The thin, fragile layer of cells lining fluid-logged or deflated alveoli lose their ability to exchange oxygen to the bloodstream. The inability to accurately monitor the BiPAP’s flow rates could worsen mortality, so the engineers are also integrating an alarm system to alert medical staff.
Working with his undergraduate industrial electronics students, Al Wicks, an associate professor of mechanical engineering, is programming a microcontroller to interpret flow meter data. This is an added safety check to give doctors peace of mind. If something happens to the machine and the patient receives too much or not enough air volume, an alarm will sound.
Altogether the measurement and alarm upgrade materials should cost less than $200. Williams’ Design, Research, and Education for Additive Manufacturing Systems laboratory is preparing to ramp up production in parts using industrial-scale 3D printing systems.
Once you have the filtration materials and sensor, the BiPAP upgrades take just five minutes to assemble according to Rubio.
“We want to make this system as cost-effective and scalable as possible so other universities and hospital systems can replicate our process,” Meadows said. “Once the programs are written, others would be able to upload our code to the microcontroller, and use a wiring diagram to connect the 3D printed flow meter to the microcontroller.”
With Meadows’ flow meter, Wicks’ alarm system, Williams’ 3D printed parts, and Rubio’s exhaust filter modifications, physicians at Carilion Clinic and potentially other hospitals can deploy a safe alternative to traditional ventilators in a dire situation. In the short-term, the doctors can use one sensor to calibrate multiple BiPAPs one at a time. As the engineers manufacture more monitoring systems, potentially ramping up to 20 units per day, they plan to install the devices in-line.
“In a perfect world, ventilators would be readily available wherever they are needed. In this unprecedented scenario that may not be possible in some hospitals. While this makeshift ventilator is not a perfect system for every patient, it could give people recovering from COVID-19 or those with less severe symptoms the breathing support they need,” Rubio said.
All devices used in patient care – even those used to address critical shortages in an emergency – require significant evaluation and approval at the hospital level.
This is just one of many research projects that Virginia Tech engineering and biology faculty are working on to help address medical equipment and COVID-19 testing kit shortages nationwide.