In "An Occurrence at Owl Creek Bridge", how might one account for Farquhar's intense sensitivity of his surroundings during and after his escape?

The heightened sensitivity can be explained as commonly occuring during times of imminent harm.  For example, sometimes when you fall down, it seems as if you are moving in slow motion, aware of everything happening around you, preparing yourself for when you hit the ground! In the same way Farquar seems suspended from time, almost standing outside of the incident, objective enough to notice details. Though this sequence is all in his imagination, his sensitivity to his surroundings was intense leading up to the hanging as well. An example would be his focusing on the floating driftwood, the seemingly loud ticking of his watch in para. 5. He knew he was about to lose all sensations, so each one was on keen alert to take advantage of his last moments.