A healthy person not needing a respirator will suffer injury or death when put on a respirator.

Respirators are only meant for those who cant breathe. Literally cant breathe on their own.

Normal functioning lungs and respiration has a very specific amount of pressure in the lungs. If you greatly increase the pressure (which ventilators do) to lungs that dont need it leads to rupture in the vessels and alveoli. Once that happens, fluids begin to build up, leading to oxygen deprivation and "drowning". The person ends up going into cardiovascular distress and dies quite quickly.