I tried to inhale,
but there was a confining tension
in my chest that
would not leave me
[shadows of death closed in].
But, from the dark depths,
a stranger appeared,
pressed hands against
chest congested with anxiety
[a shortage of hope].
He resuscitated me
though I was found
in the troughs of
an apparent demise
[self-inflicted and premature].
He filled forlorn lungs with oxygen
when I was dead inside.
I learned to exhale
on my own
[because of him].
I like the addition to your extended metaphor technique; the parentheticals at the end of each stanza really punctuate them and flesh out the rest of the piece. The piece also has a natural, if somewhat predictable, ending. It felt smooth all in all, and with the right imagery woven in (I expect no less from you these days).