The team from Oxford University and King's College London took less than a week to take the device from the drawing board to working prototype, so that it can soon help in the fight against COVID-19.
Sky News witnessed the first test on a medical dummy. It worked - the simulator's chest rose and fell.
The Oxvent is made using a standard resuscitation bag and valves widely used in the NHS, eliminating the need for 3D printing of complex parts.
Compressed air squeezes the bag, blowing oxygen into the lungs, with the frequency of 'breaths' controlled by simple electronics costing less than £100.
Andrew Orr, an engineer at Oxford University, said Sony confirmed that it could turn what is currently a jumble of wires into a printed circuit board - and produce 5000 of them in a week.
"If this is something that we can knock together in a weekend, then mass producing it will be dead simple, he told Sky News.
"You could go from this rats nest to a circuit board in a couple of days."
Covid-19 has overwhelmed well-resourced hospitals in northern Italy, alarming doctors in Britain.
The NHS has just over 8,000 ventilators, but the government says 30,000 will be needed.
Professor Andrew Farmery of Oxford's Nuffield Department of Clinical Neurosciences said the Oxvent's design lacks the "bells and whistles" of modern ventilators, but is safe and reliable.
"The beauty of it is its simplicity," he said.
"We have gone back to the state of ventilators 10-15 years ago. We have used components that we already have on the shelf, which is important when the supply chain is stressed. We have repurposed them."
"The design can't break, there are no motors to burn out and there are no parts to snap. It can be assembled in a less than two hours from the plans we will make freely available to any manufacturer."
The Oxvent team pitched their design to the Cabinet Office on Monday and two hospitals have said they are ready to test it on patients.
Professor Sir Mark Walport, chief executive of UK Research and Innovation, said the team was "working very hard with the business community who are really pulling their fingers out and working very hard on a variety of fronts to build new ventilators and make sure as many as possible are available".
"But to be honest, there isn't a country in the world that has the stocks of ventilators that are needed when you have a pandemic like this."
More than 60 companies have responded to the Prime Minister's call for help in producing ventilators.
Manufacturers such as Vauxhall and Airbus have said they could 3D-print parts and assemble devices.