Which diagnostic measurements are relevant in the workup of panic disorder?

Updated: Mar 21, 2018
  • Author: Mohammed A Memon, MD; Chief Editor: Randon S Welton, MD  more...
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Room air pulse oximetry values are usually within the reference range or at the upper limit of the reference range. End-tidal capnography values are typically less than 30 torr during hyperventilation.

Arterial blood gas analysis is useful in confirming hyperventilation (respiratory alkalosis) and excluding hypoxemia or metabolic acidosis. The presence of hypoxemia with hypocapnia or a widened alveolar-arterial (A-a) gradient should increase the suspicion of pulmonary embolus.

Electrolyte analysis is unnecessary, although several abnormalities may be present in the setting of hyperventilation. Serum phosphorus and ionized calcium may be diminished in patients with hyperventilation and carpopedal spasm, Chvostek sign, or Trousseau sign. The serum calcium level may be within the reference range.

Human subjects with panic anxiety have elevated levels of orexin in the cerebrospinal fluid. Orexin, also known as hypocretin, is thought to play an important role in the pathogenesis of panic in rat models [31] ; it is also a potential gene of risk for panic disorder.

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