Stage 1. You’ve had debilitating symptoms for a few days, but now it is so hard to breathe that you come to the emergency room. Your oxygen saturation level tells us you need help, a supplemental flow of 1 to 4 liters of oxygen per minute. We admit you and start you on antivirals, steroids, anticoagulants or monoclonal antibodies. You’ll spend several days in the hospital feeling run-down, but if we can wean you off the oxygen, you’ll get discharged. You survive.

Stage 2. It becomes harder and harder for you to breathe. “Like drowning,” many patients describe the feeling. The bronchodilator treatments we give you provide little relief. Your oxygen requirements increase significantly, from 4 liters to 15 liters to 40 liters per minute. Little things, like relieving yourself or sitting up in bed, become too difficult for you to do on your own. Your oxygen saturation rapidly declines when you move about. We transfer you to the intensive care unit.

Stage 3. You’re exhausted from hyperventilating to satisfy your body’s demand for air. We put you on noninvasive, “positive pressure” ventilation — a big, bulky face mask that must be Velcro’d tightly around your face so the machine can efficiently push pressure into your lungs to pop them open so you get enough of the oxygen it delivers.