Israeli researchers have devised a sniff-test using shampoo and rotten fish, to determine if brain-injured patients have a chance of recovery. If the patient showed a predictable response, that person had a 100% chance of recovering consciousness and a 92% chance of surviving 3+ years.
https://www.israel21c.org/sniff-test-can-predict-if-brain-injured-patient-will-wake-up/