Coding corner

How to code nuclear medicine perfusion and ventilation studies

Proper coding of nuclear medicine perfusion and ventilation scans of the lungs can be confusing. Confusion among coders causes coding inconsistency, resulting in improper coding, putting a provider at compliance risk or at financial risk.

Clinical overview

How well a patient is getting oxygen into their blood (and carbon dioxide out) generally requires measurement of two things: how well the blood is getting down into the capillaries surrounding the tiny little alveoli in the lungs (perfusion), and how well the oxygen is getting down into those same little alveoli (ventilation). In order for the oxygen/carbon dioxide hand-off to occur, both the blood and the gases need to be able to get to where they belong to where they can interact and there can't be a plug in either system in the blood stream nor the lungs.

Often, patients will have a V-Q test, also called a VA/Q test. Here are the technical details:

Ventilation/perfusion ratio: the ratio between the amount of fresh air brought into the alveoli in the lungs and the amount of blood flow past the alveoli in the lungs.

VA (Ventilation of the alveoli) (normally about 4 liters per minute): amount of air going into and out of the alveoli for the whole lung.

Q (Cardiac output = Perfusion of the alveoli) (normally 5 liters per minute): amount of blood flowing to and perfusing the alveoli of the whole lung.

Normal VA/Q ratio = 0.8

VA = 4 liters per minute        =    4      =     0.8 ratio for the whole lung

 Q   = 5 liters per minute              5 

It is the ratio of ventilation to perfusion that is most important in gas exchange, not the individual values of ventilation and perfusion.

The VA/Q ratio in a patient can be higher than normal (indicating dead space) in a patient (for a number of clinical reasons) or, of course, it can be lower than normal (right to left shunt) in a patient for other clinical reasons. You can find more detailed explanations of what abnormal an VA/Q ratio might mean at:  http://www.nursing.uiowa.edu/sites/users/lmarshal/webphyspath/160pdf/respir.pdf

By using scintography, the exact location of any radioactivity can be identified and imaged. The patient can have radioactive material injected into his bloodstream intravenously and scintography imaging can show if there are any parts of the lungs where the radioactive blood just cannot get to (due to some kind of plug in the bloodstream). Similarly, the patient can inhale radioactivity and scintography imaging can show if there are any parts of the lungs where the radioactive gas just cant get to (due to some kind of plug in the lungs or bronchioles). Any non-perfused or non-ventilated areas will show up due to the lack of radioactivity in those areas.  

Note that if the patient had just a perfusion study, there is just one CPT code that would be assigned: 78580.  If a patient had just a Ventilation study, there are five different possible CPT codes that could describe the service and the coder will need to select the right code out of the five possible choices: 78586 78587, 78591, 78593, or 78594.  Lastly, if the patient had a combined perfusion and ventilation study, there are three different possible CPT codes that could describe the service and the coder will need to select the right code out of the three possible choices: 78584, 78585, or 78588. 

Proper coding

The simplest way to proceed is to determine if radioactive isotopes were provided to the patient via just a blood stream injection (a perfusion study) or via inhalation either of a radioactive gas such as Xenon, or of oxygen that has been aerosolized with particles of a radioactive substance (a ventilation study). Of course, if both the injection and the inhalation were done, then that means both a perfusion study and a ventilation study were done.

To determine if a perfusion was done, obviously look for perfusion language in the report. Also look for language that indicates the injection of radioactive isotopes into the bloodstream:

  • Tc-99m-MAA
  • Macroaggregated Albumin
  • Technetium MAA
  • Macrospheres
  • Perfusion

You will need to see language such as this in order to confirm that the perfusion service was provided.

Next, you will need to determine if the ventilation portion was performed. You may see clear documentation, such as the word ventilation. Further, in order to properly code these services, you will need to know if the patient inhaled a radioactive gas (generally Xenon), or if the patient actually inhaled oxygen that had been aerosolized with particles of a radioactive substance.

The language that relates to gaseous radioactivity might include:

  • Xenon
  • Xenon gas
  • Gaseous
  • Xenon-133
  • Xe 131
  • Krypton
  • Krypton gas
  • Krypton-81
  • Kr 81

 Language that relates to oxygen that has been aerosolized with radioactive particles might include:

  • DTPA
  • Tc-99m
  • Technetium DTPA
  • Particulate
  • Mist
  • Aerosol
  • Aerosolized

The last thing you will need to determine is if there was just a single breath taken of this radioactive gas/aerosolized oxygen to see how well the radioactivity can get to all parts of the lungs, or if there was also rebreathing/washout with plain non-radioactive oxygen, to determine how long and how many breaths it takes for the patient to clear the radioactive material out of the lungs.

It may be a bit trickier, but language that may indicate there was imaging to determine how long it took to wash the radioactivity out of the lungs or that even after breathing oxygen for a time, the patient couldn't clear out the radioactivity, might include:

  • Equilibrium
  • EQ
  • Wash-in
  • Washout
  • Rebreathing
  • Air trapping
  • Gas trapping
  • Clearance

Lastly, the images may be and generally are taken in just one plane (usually A/P). However, sometimes imaging in another plane, often lateral, is done, too. So images may be done in just one or in multiple planes.

Knowing if perfusion and/or ventilation were done, if radioactive gas or simply oxygen aerosolized with radioactive particles were used, and if the imaging attempted to determine if and how well the patient was able to rid his lungs of the radioactivity by multiple breaths (and, of course, how many planes were imaged) are all that you should need to know in order to select the proper CPT codes.

Perfusion only 78580

Gaseous ventilation only, single breath, single plane 78591

Gaseous ventilation only, with washout, single plane 78593

Gaseous ventilation only, with washout, multiple planes 78594

Aerosol ventilation only, either single breath or with washout, single plane 78586

Aerosol ventilation only, either single breath or with washout, multiple planes 78587

Perfusion with gaseous ventilation, single breath, single plane 78584

Perfusion with gaseous ventilation, with washout, single plane 78585

Perfusion with aerosol vent., either single breath or with washout, single or multiple planes 78588

Please note that while the official descriptions for codes 78584 and 78585 do not contain the term gaseous, the March 1999 issue of the AMAs official newsletter The CPT Assistant makes clear that these two codes are to be construed to mean gaseous ventilation. The March 1999 issue of The CPT Assistant is a valuable issue with regard to perfusion and ventilation studies.

Greg Schnitzer, CodeRyte, Inc.

Revised November 2, 2007