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Univ. Engineers Convert CPAP into Ventilator

CPAP-ventilator system

Michael Zabala, left, and Tom Burch with their prototype CPAP-ventilator system (Auburn University)

8 Apr. 2020. An engineering group found a way to adapt a CPAP machine into a mechanical ventilator, a device for people needing breathing help from Covid-19 infections. Researchers from the engineering and veterinary medicine schools at Auburn University in Alabama say they completed tests of a prototype device with a large animal, to prove the concept and advance the technology.

People with advanced forms of Covid-19 infections often develop a condition known as acute respiratory distress syndrome, or ARDS, a life-threatening complication where fluid leaks into the lungs, The fluid build-up makes breathing difficult and adequate oxygen does not get to the body. ARDS is often triggered by injury to the lungs, and in the case of Covid-19 infections, from inflammation reacting to the SARS-CoV-2 virus responsible for the infections.

Mechanical ventilators help people in intensive care with ARDS breath. A tube is inserted in the patient’s mouth or nose, through the windpipe to the lungs, with the ventilator sending oxygen from an external source into the lungs. For people with Covid-19 infections, ventilators provide breathing help to allow lungs to heal and the infection to pass. Hospitals in states and communities hard hit by Covid-19 are warning health authorities that their supplies of mechanical ventilators, which can cost tens of thousands of dollars each, are rapidly becoming depleted.

Auburn mechanical engineering professors Michael Zabala and Thomas Burch looked into the prospect of quickly and inexpensively adapting a CPAP machine, which helps people breath with obstructive sleep apnea, into a mechanical ventilator. In obstructive sleep apnea, upper passages of the airways close up during sleep, interrupting one’s sleep and breathing, and preventing oxygen from getting into the lungs. CPAP stands for continuous positive airway pressure, and the machine, worn at night with a face mask, increases air pressure in the throat to prevent the airways from collapsing.

The Auburn engineering faculty, with undergraduate engineering student Hayden Burch, hypothesized a CPAP machine could perform many of the same functions as a mechanical ventilator, and started a project they call Re-InVent to build a prototype. Their device would need to start with a common CPAP machine, be built quickly and inexpensively with readily available parts, yet still operate for several hours at a time.

By 2 April, the Auburn team completed bench testing of its prototype, based on a commercially available CPAP device. The researchers say their system adds parts that can be purchased today for about $700 to a CPAP machine, and assembled into a working mechanical ventilator in about four hours.

The engineers turned their device over to colleagues at Auburn’s veterinary medicine school for testing on a 200-pound Boer goat, an animal with lungs similar in capacity to humans. Stuart Clark-Price, professor of anesthesiology at the school, supervised testing the Re-InVent device with the goat. “In our test,” says Clark-Price in a university statement, “we were able to ventilate the goat and safely maintain appropriate oxygen content [in] his blood. Then he was brought out from under anesthesia and fully recovered to return to normal activity.”

The team is now upgrading the prototype allowing for two CPAP machines working in tandem to double the pressurization capacity. “Essentially, we are using a CPAP machine to pressurize the air inside an air-tight compartment, and then another CPAP machine to pressurize that pressurized air,” notes Zabala.

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