Ventilatory Physiology of Patients With Panic Disorder

• Thirty-one patients with DSM-III panic disorder or agoraphobia with panic attacks, 13 normal controls, and 12 patients with other anxiety disorders were studied during ventilatory challenge with room air hyperventilation and 5% carbon dioxide inhalation. Patients also underwent sodium lactate infusion. Among the patients with panic disorder, 58% panicked with sodium lactate, 39% with 5% CO₂, and 23% with room air hyperventilation. Of the other patients, four panicked with sodium lactate, none with 5% CO₂, and one with room air hyperventilation. One normal control panicked with both sodium lactate and 5% CO₂. Panic with CO₂ was associated with an exaggerated ventilatory response and increases in plasma norepinephrine level and diastolic blood pressure. Patients with panic disorder may have hypersensitive CO₂ receptors that, when triggered, evoke a subjective panic associated with an exaggerated ventilatory response and consequent hypocapnic alkalosis.