I cannot begin to grasp what it must have been this experience for this poor man, but I can very vaguely imagine. A recent book and film used the metaphor of a diving bell. You are inside your body as if you are inside a diving bell. It's alright when you can control your diving bell. You swim around and interact with all other beings in diving bells you encounter. Suddenly something happens and you loose control of the diving bell. Your life as such is not threatened; but you can't communicate any more, you can't interact. You are trapped inside.