The instrument sends sound waves into the heart, which then are reflected back to form a moving image of the beating heart's structure on a TV screen. A record is made on paper or videotape. The moving pictures show how well the heart is functioning. In these procedures, the patient, with a nose clip in place, breathes in and out through a mouthpiece. The patient's breathing displaces the air held in a container suspended in water.
Some devices measure air flow electronically.
This restriction is thought to be due, in part, to the increased stiffness of the lungs resulting from both the changes in the structure and the high blood pressure in the pulmonary arteries. In the perfusion scan, the doctor injects a radioactive substance into a vein. Immediately after the injection, the chest is scanned for radioactivity. Areas in the lung where blood clots are blocking the flow of blood will show up as blank or clear areas. A major reason for doing a perfusion scan is to distinguish patients with PPH from those whose pulmonary hypertension is due to blood clots in the lungs.