I don't know if this fits into your research that you are conducting, but I wanted to share a personal experience which my sisters and I had just recently at the passing away from my father. My father was put on life support as a request from my sisters to the doctor as I had not arrived yet. It took me two days in travel to reach him. In the meantime, my sister kept talking to him saying to hold on as I was on my way. I arrived at the hospital at 4pm, and I got my share of time to talk to him and assure him I was well and happy. I had wished he would open his eyes, say something or show some movement. But we also knew that just happens very rarely. At the second session with him in the ICU, we prayed and meditated and told him to go. By 9 pm we got the call from the hospital, he has passed away in peace. I believe hearing is the last thing that goes, this is from my experience. He held on when they told him and he let go when we told him.