wasn't there a crowd effort to make and mass 3d-print ventilators? I guess I've seen in couple of days ago on reddit
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.