A loud hiss and grunt come from a green bag pressing air through a tube, as Senegalese researchers work to develop a prototype ventilator that could cost $160 each instead of tens of thousands of dollars.

The team is using 3-D printed parts as it works to find a homegrown solution to a medical shortfall that has struck even the richest countries: how to have enough breathing machines to handle an avalanche of COVID-19 patients who need the devices to help increase their blood oxygen levels.