Why (not) make ventilators?
Acute Respiratory Distress Syndrome (ARDS), in which breathing is impaired by fluid buildup in the lungs, is one of the most common severe complications of COVID-19. Patients with ARDS frequently require mechanical ventilation to survive. According to the American Hospital Association, it is possible that up to 900,000 people in the United States may need mechanical ventilation during the COVID-19 pandemic. The Society of Critical Care Medicine estimates that approximately 200,000 are currently available, though exact numbers are not known. If ventilator production could be quickly increased, this would make it possible to care for more critically ill patients.
Mechanical ventilation requires careful supervision by trained respiratory therapists in order to avoid complications, including permanent lung damage. Without sufficient medical professionals to use them, adding to the supply of ventilators will not improve the treatment of COVID-19 patients.
This does not mean that no one should be working to increase ventilator supply, but it does mean that other supplies (e.g. PPE) may be of more direct use to those who are treating patients. If you do not have knowledge or experience of mechanical ventilation and are not working with someone who does, you may be better off focusing on other projects.