I was also shown that the inner breathing of the people in the earliest church, which had flowed from the navel toward the deeper areas of the chest, had altered as time passed—that is, had altered in their descendants. It had withdrawn more toward the back and the belly, or more toward the surface and downward, until finally in the last generation of that church (the generation right before the Flood), hardly any internal breathing remained. In the end, when the breathing inside the chest disappeared, they spontaneously suffocated.
In some people, though, external breathing then took hold, as did articulated sounds, or verbal speech.
As I was shown, these are the ways people living before the Flood breathed, depending on the state of their love and faith. In the end, when there was no longer love or faith but only a convinced belief in falsity, internal breathing stopped, as did direct communication with angels and perceptive knowledge.
from Secrets of Heaven, Volume 2, Section 1120