Makes me wonder what would it take to 3D print other life saving devices? And are there designs online in the public domain ?
A few studies suggest it could be done: https://www.ncbi.nlm.nih.gov/pubmed/18164798 https://www.ncbi.nlm.nih.gov/pubmed/16885402
Could be faster than building new ventilators.
Too much volume (or pressure, depending on the control mode) can injure the lungs, too little and you're not addressing the underlying problem very well.