A ventilator is a machine that supplies oxygen to the lungs of a patient with severe respiratory problems when oxygen levels in the patient's bloodstream drop below a certain point. So that the ventilator can deliver oxygen to the patient, a tube is placed down the patient's throat, or intubation, to open up the patient's airways. Many hospitals in the U.S. face possible ventilator shortages as the number of COVID-19 cases continues to spike.