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. The
healthcare professional may order a pulmonary ventilation scan
in the following circumstances: the person has chest pain or
shortness of breathresults of the person's pulmonary function
tests are abnormala woman is on oral contraceptives and shows
signs of a pulmonary embolus, or a blood clot to the lungsin a
person with leg pain, to evaluate whether a clot from a leg vein
may have broken off and traveled to the lungan individual has
breathing problems after surgery 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 per