Take it, Wikipedia:
YMMV, grain of salt (heh), consider the source, citations needed, etc., but references are found outside Wikipedia. Assuming that it is accurate, would the amount of pain added by salting a wound really matter at that point? Or was there some other purpose?
To add in salt to injury.
Oh, snap!
I’m sure they would be unconscious in seconds and dead in minutes, because as soon as the thoracic cavity is breached the diaphragm wouldn’t be able to pull air into the lungs. You would asphyxiate.
The lungs fill by negative pressure; put a hole in the sealed chest cavity and your lungs won’t inflate.
I can’t see how salt would matter, you would never know. Of course, you wouldn’t scream as no air would be able to get past your vocal chords to make a sound.
see: sucking chest wound
A few years ago I toured a museum of torture in France where we saw some of the most horrific ways of inflicting pain that anyone could devize.
It was explained that there was no wish to extract confessions or information as anyone would admit to anything and the mere threat would be enough to elicit any information they might have. The main purpose of torture was as a threat to others to keep them in line, so the louder and more prolonged the screams, the better.
I forget which episode, but The History Channel’s show, The Vikings, showed this once. IIRC, they showed it from the front, but it was very difficult to watch (at least for me).
Also featured in 1001 Ways To Die on SPIKE tv.
I can’t be arsed to learn dead languages and read everything from back then, but none of the quotes Wikipedia include mention the salt thing.
My WAG - someone has conflated salting smaller injuries as punishment with the blood eagle, either in modern times or in one or a small minority of “period” mentions.
I’ll give a hint: the title involves a bodily fluid and some sort of raptor.
My WAG - its a vandal, trying to be funny - absurd humour, black humour, or they like the idea of trying to create the fact… hoping someone will copy it… like in a tv show when they do research only from wikipedia…
Ahhh, the memorable Spit Falcon episode.
I thought that this thread title looked familiar! 
Probably useful to remember that there was an audience that a point was being made to. Salt or no salt it’s a gruesome and horrible way to be executed. To literally add salt to the wounds may have been theater of going even further at making the point to those not being executed. Like the Spinal Tap amp that “goes to 11” where do you go when you are already chopping open their rib cage and pulling out their lungs? You add salt. This execution goes to 11.
AFAIK (and I haven’t read the Wikipedia entry) the purpose of the blood eagle and similar tortures was actually benevolent. For a very long time, the Vikings believed that the only ways to reach a pleasant afterlife were to drown during a sea voyage or to die in glorious battle. Torturing a captive to death gave them a chance at Valhalla. They didn’t want to intimidate or punish anybody. They wanted to reward the brave captive with a wonderful afterlife.
I imagine that exsanguination would occur long before any symbolic sprinkling of salt or indeed before suffocation. Regardless, if the victim somehow remained not just alive but also conscious, they would be dealing with huge lacerations, many broken bones, severed muscles, severed nerves, and hacked up connective tissue. I don’t imagine that a sprinkling of salt would even register.
Nitpick: sucking chest wounds generally aren’t big enough to have an effect on the ability to create negative pressure. They’re bad because air (and blood) get sucked into the space surrounding the lung, and as a result the lung, which is pretty much just a fleshy balloon, can’t inflate properly. The space between “puncture to chest wall” and “struggling to breathe” isn’t necessarily instantaneous.
From other events in the sagas it appears it was enough to die by the sword rather than sick in bed. Stabbing your prisoner through the heart with a sword would be sufficient to give them a trip to Valhalla. The available sources also speak of the blood eagle in terms of punishment, so your unsourced conjecture should be given little weight.
Perhaps the salt had a different use then intending to inflict additional pain, such as preserving the body so it can be displayed longer, or effecting the outflow of blood, or giving it a certain look?
The GQ answers to this question are:
There was no salting.
Salt would not matter at this point even if there had been any.
“Other purposes” have no meaning when there was no salting.
This couldn’t possibly be a GQ answer. There’s no citation to a reputable source, just bald unsupported assertions.
That never happens in GQ. Right?
See my first answer in the thread. There’s no way to cite a negative, but the wikipedia article the OP references has no site for the salting part and all the references it does have clearly leave out salting the wounds. No one has come by the thread to give a site for the salting either.
Speculating on why one might want to salt a wound that’s already killed the victim may be some people’s idea of fighting ignorance. It isn’t mine.