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Engineer creates open-source ventilator for COVID-19 patients

A University of Leicester-based engineer has created an innovative new ventilator designed to help COVID-19 patients.

Dr Paul Lefley’s solution uses 3D-printed mechanical parts and basic electronics to replicate the action of a medical professional using an ‘ambu bag’ – or artificial manual breathing unit – and can run for up to 24 hours on internal batteries.

The project is one of a number of collaborations under the ‘Nairobi Alliance’, a strategic partnership between the Universities of Leicester, Nairobi (Kenya), Malawi, Rwanda and Witwatersrand (South Africa).

For this project, Dr Lefley worked in close collaboration with Dr Stanley Mlatho from the University of Malawi, driven by a shared goal to improve vital health support in low-resource settings in the face of the coronavirus pandemic.

The new design uses a simple double cam system to squeeze the bag as a human doctor or nurse would. However, the reciprocating mechanism does not simply alternate between squeezing and releasing the bag. The time taken to compress the bag (inhale) is twice as long as the release time (exhale), thus maintaining a positive pressure in the lungs of the patient for longer to aid in the uptake of oxygen.

The ventilator is powered by an in-built rechargeable lithium battery, which means that the unit could be used in environments where mains power is not always guaranteed, and Dr Lefley hopes to release open-source plans for his solution.

Dr Lefley, lecturer in the School of Engineering, said:

“I’d come across one or two things online where other engineers around the world had done similar things in a more crude way, with a device to squeeze the ambu bag, but I thought we could do better than that.

“Inflating the lungs with a positive pressure helps with the uptake of oxygen into the bloodstream, and that’s designed into the mechanism. This gives the patient a longer, deeper, intake of breath followed by a shorter exhale.

“It has been shown that the most serious COVID-19 cases benefit from continuous positive airway pressure, which is akin to what a continuous positive air pressure (CPAP) ventilator can do, but without the forceable cyclic breathing action of a reciprocating ventilator.

“The mains power is purely there to recharge the batteries in order to give the device an uninterruptable power supply, which means it is suited to environments where the mains power might come and go throughout the day.”

Dr Mlatho, senior lecturer in physics and electronics at the University of Malawi, said:

“Malawi faces an acute shortage of medical equipment and the situation has worsened with the COVID-19 pandemic. A huge shortage of ventilators and CPAP machines in our hospitals has necessitated the need to innovate ventilators and other machines to cater for patients in need of breathing aid.

“The ventilator developed by the University of Malawi is based on a manual resuscitator that has been automated and operates with one mechanical arm and is able to measure air flow rate, air pressure and patient oximetry.

“This design has modes for pressure control and is able to synchronise with the breath in and out of the patient, and can send data to a central medical attendant to cater for medical personnel shortage.”

Dr Lefley will now work closely with Dr Mlatho and engineers from the University of Malawi, who have been developing a CPAP ventilator of their own, to discuss the possibilities of scale-up and rollout of the devices.

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