While we live in these earthly bodies,
we groan and sigh,
but it's not that we want to die and
get rid of these bodies that clothe us.
Rather, we want to put on our new bodies
so that these dying bodies will be
swallowed up by life.
II Corinthians 5:4 (NLT)
Kim talks about SIGHING
The physiological factors behind a sigh are well described HERE in a Discovery Health article.