Which diagnostic exam is very invasive but extremely accurate for diagnosis of a P.E.

The diagnostic exam that is very invasive but extremely accurate for the diagnosis of a Pulmonary Embolism (P.E.) is a Pulmonary Angiography.

Here are the steps of how it is performed:

1. The patient is positioned on the examination table.

2. A local anesthetic is applied to the area where the catheter will be inserted.

3. A small incision is made at the site.

4. A catheter (a long, thin, flexible tube) is inserted through the incision into a large blood vessel and guided to the pulmonary artery.

5. A contrast dye is then injected through the catheter and X-ray images are taken.

6. The images will show if there's a blockage in the blood vessels in the lungs, indicating a pulmonary embolism.

7. After the procedure, the catheter is removed and pressure is applied to stop any bleeding. The opening in the skin is then covered with a dressing.

8. The patient's vital signs are monitored during recovery.

This procedure is considered invasive due to the need for a catheter insertion and it carries risks such as damage to the blood vessels, reaction to the dye, and infection. However, it provides very detailed images of the blood vessels in the lungs, making it extremely accurate for diagnosing a P.E.