A 26-year-old woman presents with recurrent unexpected panic attacks over the past 4 months, accompanied by persistent fear of future attacks and avoidance of shopping malls and public transit. She meets DSM-5 criteria for panic disorder with agoraphobia. She is referred for cognitive-behavioral therapy. During session three, her therapist guides her through breathing exercises designed to intentionally provoke mild dizziness and chest tightness in a controlled setting.