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Pulmonology Coding Alert

Reader Questions:

Aerosol and Gaseous Tests Set Apart

Published on Fri Jan 28, 2011

Question: What's the difference between aerosol and gaseous ventilation?

Answer: Both aerosol (78586, 78587) and gaseous (78591, 78593, 78594) studies are part of the ventilation code series.

Aerosol tests involve the patient inhaling nebulized (reduced to a fine spray) aerosol agents with radioactive particles. The key term to look for indicating aerosol is "DTPA," the radioactive aerosol the provider has the patient inhale. Sometimes you would encounter other terms such as Technetium DTPA, particulate, and mist.

Physician's note for gaseous ventilation studies usually refer to the gas used, typically Xenon gas (such as Xenon-133 or Xe 133). Another possibility is Krypton gas (Krypton-81 or Kr 81), although you may not see this much in practice.

CPT further distinguishes gaseous ventilation studies by whether the patient takes only a single breath or the patient does rebreathing and washout with plain oxygen. "Rebreathing" is inhalation of the gas previously exhaled. "Washout" is the elimination of the radioisotope from the lungs. The xenon gas exams typically consist of three phases:

  • a single breath -- the patient takes a single deep inhalation
  • rebreathing -- the patient takes normal breaths while rebreathing a mix of oxygen and xenon
  • washout -- the patient breathes room air while exhaling the xenon, clearing the lungs of the radioactive gas.

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