Maybe anyone can't, but, uh.
A character with 5 hp out of 80 is exhausted. Not status-effect exhausted, exhausted if you want to pose his mood. He has been warding off or absorbing blows for some time and doesn't know if he's up for another burst of that effort. He has taken one bloody wound, maybe a medium-deep graze on his arm or maybe his chainmail got shoved into his chest and he'd rather leave it there for the time being. If something actually connects solidly he's going to crumple, unless it couldn't back off a puppy to begin with or fate is feeling very kind.
But he is not "slowed", he is not "weakened", he is not "dazed". (At least not inherently. He may have been tagged with one of these effects until the end of the encounter.) He can still move around the battlefield and deliver full-force swings, maybe pausing briefly to muster up the effort but either adrenaline or will or both is keeping him going. Just as long as he doesn't have to stop.
If he can catch his breath for a moment (has his second wind available and a healing surge to burn) he'll feel a little less put through the wringer, maybe able to stave off a couple more shots, but not up to worrying about the wound (the healing surge won't get him above bloodied). If he's been holding back any desperation moves (only usable when bloodied) then now is the time. And everyone can see or sense that he's wounded, so anything that affects bloodied characters differently affects him.
If he receives another healing effect that takes him up above bloodied then he tends to his wound - bandages his graze or closes it through sheer force of flex, or finally essays to pull the chainmail out and winces for a moment, but it's not biting into his skin anymore. This also happens if he has time to take a short rest and has healing surges to spend.
If he's still at 5/80 after his short rest, then he just doesn't have anything left in reserve today. He doesn't get any worse while he rests, but he doesn't get any better either.
I suppose you could house-rule that anybody who was bloodied could clear that condition during a short rest but it would return as soon as they took damage.