Have you considered "diaphragmatic breathing" as a treatment for Panic Attacks?

[David]

Diaphragmatic breathing, abdominal breathing, belly breathing, seesaw
breathing, deep breathing is the act of breathing deep into your lungs
by flexing your diaphragm rather than breathing shallowly by flexing
your rib cage. This deep breathing is marked by expansion of the
stomach (abdomen) rather than the chest when breathing. It is
generally considered a healthier and fuller way to ingest oxygen, and
is often used as a therapy for hyperventilation and anxiety disorders.

Note that some yoga and meditation traditions draw a clear distinction
between diaphragmatic breathing and abdominal breathing or belly
breathing. The more specific technique of diaphragmatic breathing is
said to be more beneficial.

Though the diaphragm is the primary breathing muscle, it is believed
that many people have little sensory awareness of their diaphragm and
almost no idea of how to engage it more fully or even of how it works.
There are some breath therapists and breathing teachers who believe
that because of the increasing stress of modern life and the resulting
over-stimulation of the sympathetic nervous system, as well as of the
idealized hard, flat belly, that many people carry excessive tension
in the belly, chest, and back, and this tension makes it difficult for
the diaphragm to move freely through its full range of motion.

The idea behind diaphragmatic breathing is that this is one way to
control the autonomic system which is responsible for the "fight or
flight" reaction that precipitates a panic attack episode.

I have been advised to do this exercise twice a day, once in the
morning and once in the evening, preferably prior to eating. The
suggestion was to perform this exercise 20 minutes per occurrence
(twice a day) for three months for "real" results but already am
noticing results having only performed this exercise 18 times (a bit
more than one week).

I would love to hear feedback from others who may have approached
their panic symptoms with this technique and what results you may have
experienced (good or bad).

Thanks

David