Response to hyperventilation in a group of patients with panic disorder

Twelve patients with DSM-III diagnoses of panic disorder and four normal volunteers were studied during hyperventilation of room air and increased ventilation stimulated by 5% CO₂. Patients also underwent sodium lactate infusion. Eight of the patients had a panic attack during sodium lactate infusion, seven during CO₂ inhalation, and three during room-air hyperventilation. Since CO₂ increases the firing of the locus ceruleus, and since sodium lactate infusion is known to increase cerebral CO₂, these findings are consistent with other evidence implicating the locus ceruleus in panic anxiety.