Biofeedback can help with anxiety problems. It’s not the only way; if medication has been sufficient and side effects are minimal, then that approach may be sufficient.
Psychotherapy involves changing your thinking (reinterpreting, self-talk, insight and understanding). That process is often valuable for overcoming chronic anxiety. But physical changes are usually present in panic attacks, phobias, and anxiety states. So learning to reduce things like rapid heart rate, sweating, excessive breathing, dizziness, and muscle tension, builds a sense of control over both the physiology and the associated fearful thoughts and feelings.
You can observe these responses easily with biofeedback instruments, and can also learn to control them as they happen. Moment-to-moment feedback lets you experiment with provoking and reducing various components of your fight-or-flight response.
For example, below is a sample trace of a skin conductance (GSR) response to a man recalling an embarrassing social moment. Sweat glands on his hand became more active, causing the line to jump. 
By watching such a display while focusing on a disturbing thought and then practicing relaxation, you learn to diminish the surge of anxiety that consists of both uneasy sensations and distorted thinking. Heart rate, breathing, muscle tension, and hand temperature can also be used for this purpose.
With practice, the skill becomes internalized so
that the biofeedback is no longer needed.
PANIC AND BREATHING
Panic attacks are very often associated with hyperventilation. Excessive breathing disrupts the blood’s acid-base balance, causes blood vessels to constrict, and interferes with clear thinking by reducing blood flow to the brain. Being able to keep your breathing within normal limits restores normal blood chemistry and brain circulation, and the panic usually subsides.
The breathing trace above shows lower peaks during a brief interval of hyperventilation (the CO2 number should generally stay above 35). If you haven’t found a good solution yet to panic attacks, this biofeedback method is worth trying.
The site freespira.com describes one way to change your breathing pattern using a special-purpose breathing biofeedback device. Assuming that hyperventilation contributes to your panic attacks, the Freespira program helps you change your habitual breathing pattern. This can be done usually in a few weeks of systematic daily practice combined with cognitive changes. The website contains authoritative information about this approach to panic attacks.
In my office I can use a capnometer to test your breathing for evidence of a low-CO2 pattern, and help you decide whether to proceed with the Freespira device or some other way. The capnometer can be used for biofeedback also.
Chris Gilbert, PhD, psychologist 