Final answer:
A short vest-type immobilization device is applied to immobilize the patient's torso during the rapid extrication process.
Step-by-step explanation:
The patient's torso is immobilized during the rapid extrication process by applying a short vest-type immobilization device. This device is specifically designed to stabilize the torso and prevent any unnecessary movement or potential injury. It provides support and ensures that the patient's spine remains aligned during the extrication.