Ventilation Perfusion Scan

What is a Ventilation-Perfusion (VQ) Scan?

A ventilation-perfusion (VQ) scan measures airflow (ventilation) and tracks blood flow (perfusion) in the lungs. A VQ lung scan is considered a single procedure, but involves two separate scans.  Both use a very restricted amount of radioactive material to capture images of the lungs. To help capture an image that measures airflow, the radioactive material is inhaled through a nebulizer. To help capture an image that tracks blood flow, the radioactive material is injected through a vein in the arm.

When Would You Need a VQ Lung Scan?

A VQ scan test is used to detect a pulmonary embolism, which is a blood clot on the lung. The procedure may be scheduled if a patient is experiencing the following symptoms:

  • Chest pain
  • Difficulty breathing
  • Rapid heart rate
  • Decreased oxygen in the blood

Your doctor will look for risk factors before ordering a VQ Lung Scan for pulmonary embolism. Risk factors include lifestyle habits such as smoking, nutrition, and physical activity. Individuals who sit for long periods of time are at particular risk. Immobility might stem from travel, recovery after surgery, or a dormant lifestyle. These risk factors can result in a VQ test for blood clots.

How to Prepare for a Ventilation Perfusion Test

The Ventilation Perfusion Test takes approximately 45 minutes. You will lay on an examination table while the medical technician arranges the intravenous line (IV). The line will be inserted into a vein on your hand or your arm. You might experience slight discomfort from the IV line.

Using the IV line, the technician will inject radionuclide dye into your bloodstream. This dye might consist of low levels of radioactive technetium. After the dye is in your bloodstream, the technician will disconnect the IV line and move you to a special scanner.

The scanner observes how the dye travels through your bloodstream and into your lungs. Your technician may ask you to remain still or to change positions as the scanner captures multiple images. The technician will provide you with a mouthpiece for the next part of the VQ Scan Test.

As you breathe through the mouthpiece, which includes a special gas, the scanner will snap images of your lungs. Try to avoid inhaling the gas, as it might affect the images of your lungs. The technician may ask you to hold your breath for some of the pictures.

After completing the imaging phase of the VQ Scan, your technician will remove the mouthpiece. You can then exit the scanner. Your lungs will naturally expel the gas as your breath normally.

What Happens After the Test?

Once the VQ test is complete, medical staff will monitor you for potential allergic reactions. Medical personnel will also examine you for any soreness or swelling from the IV site or any dizziness from lying prone during the test.

Once you leave the hospital, you can return to your normal diet. However, your doctor will likely ask you to increase your fluid intake to cleanse your body of radioactive substances. You might want to avoid any other procedures that involve radioactive materials for one to two days.

You may notice pain or soreness from the IV site. If you do, contact your doctor. These symptoms can indicate a possible infection.

How to Read a VQ Scan and Interpret the Results

VQ scan results are reported as normal, low probability, indeterminate/intermediate probability or high probability. Here’s how to read a VQ scan:

  • Normal: The scan showed no issues with the lungs.
  • Low probability: The results indicate the likelihood of a clot is low; more tests may be needed.
  • Indeterminate/intermediate probability: The results show the possibility of a clot; more tests may be needed.
  • High probability: The scan shows a high likelihood of a clot, and medication or perhaps a procedure will be needed to treat it.

What are the Risks?

A VQ scan is a routine procedure with minimal risks, though risks are increased for pregnant women. While a radioactive substance is used for the scan, it’s administered in very restricted amounts, passes through the body within a day, and allergic reactions are rare.

VQ Scans at Baptist Health

Patients experiencing chest pain, difficulty breathing, rapid heart rate or decreased oxygen in the blood may need to talk with their doctor about a VQ scan, which can be conducted by the medical professionals at Baptist Health.