Several weeks ago it appeared like we were running out of ventilators. Though we seem to have averted that crisis using lockdowns, there is still a possibility of a second wave of infections. Moreover there is still a huge risk of this virus having a devastating impact in the developing world.
What it does
OpenVent-B1 is a ventilator design that allows mandatory and assisted breathing modes. Volume control is quite straight-forward because of the piston design, but with the right feedback loop in software pressure control is also be possible. That includes modes like PRVC and APRV. All settings are fully adjustable, including peak inspiratory pressure, tidal volume, respiratory rate, I:E ratio and PEEP. FiO2 is also selectable as long as a pressure-regulated O2 source is available, or an O2 blender can also be used.
How I built it
OpenVent-B1 is mostly built using a combination of off-the-shelf components, and 3D printed parts. The piston pump is built out of a piece of polycarbonate tubing, with many 3D printed parts including a flexible lip seal. Besides this the design calls for 4 solenoid valves, 1 stepper motor and driver, 230V->24VDC power brick, control electronics, microprocessor, some BMP388 pressure sensors and a VL53L0X laser distance sensor. All of these can be readily bought in retail stores, and are available in quite large supply. Many of these components have alternatives available also. The entire list of major components costs around 600 euros, including the cost for 3D printing. This is using the retail prices I paid for getting the parts, so that price will come down when scaling up.
Challenges I ran into
Fitting all of the components into a neat box is tricky, because you also have to keep in mind how the plumbing and the wiring will fit in there. The resulting design currently is quite spacious, but that also allows people to substitute alternative components if the specified ones aren't available.
Accomplishments that I'm proud of
Getting the first prototype working quite quickly after learning of this problem. I'm also quite happy now with the progress on prototype 2.
What I learned
Ventilators have a long list of must-have and desirable features. It's much trickier than many people have anticipated, both in terms of functionality and in terms of reliability.
What's next for OpenVent-B1
On the design and prototyping side I want to have a PCB laid out for the control electronics, a new CPU, there's lots of firmware programming still to be done, and having a good UI will be important too. Looking further ahead there will be a lot of reliability, safety and functionality testing, which will almost certainly raise a number of issues. Further into the future I hope that the airtoall foundation or someone else will manufacture this device to help the developing world with COVID-19 and other respiratory diseases, and to help the developed world stockpile ventilators for a potential second wave, or for another novel pandemic that may come in the future.