Quick-build emergency ventilators
The GlobalVent emergency ventilator is designed to be assembled quickly and easily from cheap, widely-available parts. You can see the prototype in action in our video.
This is how it works:
- At the heart of the machine is a main pumping tube. We use a section of rainwater downpipe but any tube of similar width and a suitable grade of plastic would work. The tube is raised and lowered repeatedly into a tall bucket of water using a car windscreen wiper motor and gearbox, powered by mains supply or a car battery.
- As the tube is lowered into the bucket, water rises up inside it and pushes air out through a one-way valve, costing just a few pence, at the top. The amount of pressure is controlled precisely by the level the water is pushed up the tube. This is an important part of the design: it means safe pressure is never exceeded and there is no risk of trauma to the patient. There are also no seals to wear out.
- Air leaves the tube via the valve and is pushed along a narrower flexible pipe such as a washing machine hose. A standard diverter valve then lets air out under pressure into a third tube that takes it to the patient via a mask or directly via the windpipe. The diverter valve means the patient can’t blow air back along the same route.
- Oxygen can be added from a tank, a hospital supply or a concentrator before or after the air is pumped.
- The air exhaled by the patient can be directed through a diverter valve via another tube into a second bucket of water. This level can be set to ensure a small amount of pressure remains in the lungs to stop them deflating fully before air is pumped in again.
- The ventilator mechanism is attached to a control panel to measure air flow. The GlobalVent team is designing a module which will be compatible with a range of ventilator designs. In an emergency, the ventilator can be used without the control panel.
The parts for the GlobalVent emergency ventilator can cost less than £100. Here’s what we used:
- A windscreen wiper motor is ideal because it is a safety-critical part in a car and so is already proven. Even a poor quality motor will last for 1.5m revolutions, and about 400,000 revs are needed per patient over two weeks.
- The one-way valves in our design are standard, proven medical instrument components made by Clement Clarke and available worldwide. They cost around 5p each.
- The pump tube is made from a section of low-cost plastic downpipe used in guttering.
- The flexitube is a piece of washing machine tubing.
- We made the pump stand from extruded aluminium, but it could be made of sheet steel or anything else suitable of the right dimensions.
- The tall container for the pump could be a plasterer’s bucket or a fermentation bucket. It must have enough depth to allow the pump to rise and fall sufficiently.
- We use Milton’s sterilising tablets to keep the water clean. There is also a lid on the bucket and a lightweight plastic seal around the tube.
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