Does being put on a ventilator mean you are going to die?

Maybe not. People are placed on ventilators for several reasons. Some patients are too sleepy to breathe (as in an overdose of medications), and are supported briefly on ventilators. However, they are also used for severe lung and heart diseases when breathing fails. Sometimes the underlying disease is treatable, and sometimes not. Really depends on why the person is on the machine. Talk to the doctor.