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Researchers: Pressure-Controlled Ventilation May Be Safest Way to Connect Multiple Patients to Single Ventilator

Researchers from the University of Iowa, Boston University, and the University of Cincinnati have provided experimental evidence of a safe and independent way to connect multiple patients to a single ventilator. The researchers were assisted by the team at ProtoStudios in Iowa City to provide a 3D printed modification of a standard respiratory product in order to achieve their design.

The researchers, who tested both volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) in computer simulations and on mechanical test lungs, found that PCV lowers the risk of catastrophic lung damage and provides more control over the gas flow and tidal volume each patient receives.

David W. Kaczka, MD, PhD, associate professor in the departments of Anesthesia, Biomedical Engineering, and Radiology at the University of Iowa, says the worldwide shortage of ventilation machines has forced some overwhelmed hospitals to consider treating multiple COVID-19 patients using a single ventilator.

“There was anecdotal evidence that this could be done after the mass shooting in Las Vegas in 2017,” Kaczka says. “But there was nothing in the literature about its safety or effectiveness.”

In the Vegas example, trauma patients had roughly similar profiles in terms of their lung mechanics and needs, and the use of one ventilator for multiple patients was limited to several hours.

In the current pandemic, patients who require ventilation often have widely varying lung mechanics, Kaczka says. Even patients who have closely matched needs when they are first connected to a ventilator are likely to develop different needs over time.

“Any substantial alteration of one patient’s respiratory system — for better or for worse — could be catastrophic for all connected patients if you don’t have a way to control individual pressure and tidal volumes,” Kaczka says.

That’s why several professional societies, including the Society for Critical Care Medicine, the American Society of Anesthesiologists, and the Anesthesia Patient Safety Foundation, among others, issued a joint statement against the practice, he says.

But the expected need for ventilator options during the COVID-19 crisis demanded investigation, Kaczka says.

“The first question always is whether it’s safe. In this case, it has to be safe for every patient you connect to the ventilator,” he says. “Then it has to be effective. The patient has to be better off than if you didn’t connect them to a ventilator.”

VCV poses both safety and efficacy challenges for multiple patients, the researchers found. Gas flow shunting — where patients get more or less flow than they need — and the difficulties of ensuring proper calibration were the most concerning results of their experiments.

PCV, however, avoided most of the problems the researchers encountered with VCV.Multipatient ventilator design

“With PCV, each patient is exposed to a constant inspiratory pressure, and will receive a tidal volume commensurate with their own respiratory compliance,” Kaczka says of the researchers’ results. “In our method, each patient receives an independent PEEP (positive end-expiratory pressure), so we are able to customize the treatment for each patient as if they each had their own ventilator.”

The paper, “Shared Ventilation in the Era of COVID-19: A Theoretical Consideration of the Dangers and Potential Solutions,” includes diagrams of the necessary modifications to the breathing circuit for each patient. 

Both Protostudios and UI Ventures are part of the University of Iowa but are not related to University of Iowa Research Foundation. None of the authors has a financial relationship with Protostudios. Licensing for Oscillavent was done through the University of Iowa and managed through University of Iowa Research Foundation. Kaczka and co-author Jacob Hermann (Boston University) are co-founders and shareholders of OscillaVent Inc., and co-author Monica Hawley is an employee of OscillaVent Inc.



Friday, May 1, 2020