“How do you breathe under anesthesia?”

You don't breathe; a machine breathes for you.

It depends on the type of surgery and anesthesia, but you breathe on your own, with assistance from a ventilator, or the ventilator breathes for you.

When your anesthesiologist gives you intravenous medication to put you to sleep, you become unconscious and stop breathing. Your anesthesiologist begins breathing for you using a mask or inserts a breathing tube into your windpipe and breathes for you. Your anesthesiologist monitors your oxygenation, ventilation, temperature, blood pressure, heart rate, and motor
strength throughout your operation, then restores consciousness when the surgery is completed and you begin breathing on your own again.