GlobalVent breathing life into ventilator design to address global pandemic
A windscreen wiper motor, some water pipes and a 12volt battery sound more like a list of things to take to the recycling centre than the vital components for a potential lifesaving ventilator in the frontline fight again Covid-19.
But GlobalVent, an international collaboration of scientists, engineers and healthcare professionals in Cambridge and beyond, is taking just such low-cost and universally available parts to create freely-available, open-source designs for emergency ventilators to help save thousands of lives worldwide.
The goal is to enable reliable ventilators to be built quickly and at scale according to the materials and manufacturing options available in different locations, with a particular focus on countries with weaker and less well-funded health systems than the UK.
There are three strands to the project: ventilator designs, a generic control panel and oxygen concentrators to produce a stream of air enriched with oxygen. The ventilator concept uses pipes oscillating in a water tank to move air - the use of water allows for intrinsic safety from over-pressurising the patient’s lungs. The control panel provides critical information from any ventilator to an anaesthetist and it could become a more advanced user interface to control the ventilator’s pumping action.
One of the first to join the GlobalVent team was physicist David Harris, who has more than 25 years experience in respiratory drug delivery and is co-founder of Cambridge Healthcare Innovations, where as chief technical officer his work focuses on developing new products including inhaler technology.
From a standing start at GlobalVent about four weeks ago, he says: “Our original design values were that there are lots of people designing top-class ventilators in the UK, we are relatively wealthy and we are not going to suffer as badly as countries with limited or no health care systems, with not much money or access to technology.
“We went right back to fundamental principles. A pair of lungs acts like a balloon with a degree of elasticity and resistance, and a ventilator has to take the place of the diaphragm to get air into the lungs, and if the lung function is reduced you need to enrich the oxygen.”
GlobalVent’s ventilator design is based on standard components that can be found in most homes and cars and it would cost less than £100 to build. The basics include a water-filled 25litre bucket with a lid, one or two standard waste pipes, depending on their diameter, and two one-way valves that are the airflow inlet and outlet. Driven by a windscreen wiper motor that is powered from the mains or a 12volt battery, a crank arm with click pegs to regulate the airflow connects to a low-friction guide - similar to the bearing found on the side of a kitchen drawer - on a stand from which a piston rod pushes the tubes down into the water. This compresses air which is oxygenated and delivered to a patient’s lungs via a tracheal tube or face mask.
David says: “One of the biggest risks is that you could overpressure the lungs and cause barotrauma. Our maximum pressure is the differential height of the water inside and outside of the cylinder so it is intrinsically safe and gets rid of the need for a manometer or expensive software.”
Resilience of the system to wear and tear due to prolonged use was another guiding design principle. David says: “We have a relatively frictionless 100 per cent sealed water pump, which is good.The windscreen wiper motor is a safety-critical part of a car that’s guaranteed for 1.5million cycles, or better quality ones for 3million cycles. They are relatively cheap, maybe £20 or £30, and available around the world. They have a built-in gearbox and run off a 12volt supply.”
A further refinement of the design could be the use of a standard oil drum as the water container with a stand made of 4x2in timber secured to the side by rope, serving up to four pumps per drum.
“Our real aim is to develop and share the design with anyone who can make use of it. In many parts of the world, it is horrendous how many people die because of the lack of ventilators,” says David. “We want to say ‘take an oil drum, a piece of timber, cut it to this length, drill holes here and here’. It’s that level of simplicity.”
Everyone on the project is working for free. GlobalVent is looking for help from anyone who feels they have specific expertise required - mechanical engineers to help develop the ventilators; engineers with experience in medical device regulations, software developers and roboticists for the generic user interface; and a full engineering team to develop the oxygen concentrators. Funding or support in kind is also welcome.
Progress has been rapid and a prototype ventilator has been safety tested on an NHS training lung.
David says: “I think the biggest virtue is that it can be put together very quickly, probably in under an hour, anywhere around the world using commonly available parts. With that in mind, you can manufacture and assemble as many as you need to save as many lives as possible.”
For more information, or to get involved, visit globalvent.org.
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