Pulmonary Ventilation Scan
A pulmonary ventilation scan shows the distribution of the air a person breathes into the lung. It is used most often to diagnose a blood clot in the lung, known as a pulmonary embolus.
Who is a candidate for the test?
The healthcare professional may order a pulmonary ventilation scan in the following circumstances:
the person has chest pain or shortness of breath
results of the person's pulmonary function tests are abnormal
a woman is on oral contraceptives and shows signs of a pulmonary embolus, or a blood clot to the lungs
in a person with leg pain, to evaluate whether a clot from a leg vein may have broken off and traveled to the lung
an individual has breathing problems after surgery
How is the test performed?
For the pulmonary ventilation scan, the person is usually asked to sit upright. If the person is unable to sit, he or she can lie flat on his or her back on a table. Before the scan begins, the technologist will rehearse special breathing maneuvers with the individual. The person is asked to breathe in a radioactive gas, such as xenon-133 or krypton-81. The person will breathe the gas in and out through either a tight-fitting mask or a mouthpiece with a nose clamp. The gas gives off gamma rays, which can be detected by a "gamma camera" that is positioned over the chest. A computer then generates pictures that can be interpreted by a radiologist.
A pulmonary ventilation scan is performed on a person who is suspected of having blood clots in the lungs or other breathing difficulties. This test is normally done together with a pulmonary perfusion scan.
What is involved in preparation for the test?
The individual will undress from the waist up and put on an exam gown. All jewelry and metal objects will be removed.
What do the test results mean?
A normal ventilation scan indicates that all sections of both lungs are receiving adequate airflow. If the ventilation scan shows normal airflow to a section of a lung, but the perfusion scan shows no blood flow to that section, the person probably has a pulmonary embolus (blood clot).
If, on the other hand, the test shows that a section of the lung is not getting airflow, the person may have a pneumonia in that section. If a section is getting too much airflow, it could be an indication of pulmonary emphysema.