Final breath or at the last possible moment (4-4)
I believe the answer is:
last-gasp
(Other definitions for last-gasp that I've seen before include "Finalk expiration, moment of death" , "Done at the latest possible moment" , "Remnant of energy or final exhalation" , "Done in desperation (or at the point of death?)" , "Final exhalation before death" .)