I had a practical demonstration of the way the internal breathing of the earliest people entered silently into a type of external breathing they had and so into soundless speech. Listeners heard this speech in their inner self.
They said this kind of respiration varied in them, depending on the state of their love for the Lord and faith in him. They told the reason, too, which was that since they were communicating with heaven, they were necessarily breathing in rhythm with the angels who kept them company. Angels do have respiration, and any inner breathing keeps pace with it.
They undergo similar changes in their breathing, because when anything arises to oppose love for the Lord or faith in him, they have difficulty breathing, but when they enjoy the good cheer of love and faith, their breathing is free and full. Everyone on earth experiences something similar, but it occurs in connection with our bodily and worldly passions and our convictions. When anything opposes these, we choke, but when anything caters to them, we breathe freely and fully. These facts, however, relate to external breathing.
from Secrets of Heaven, Volume 2, Section 1119