The ventilation-perfusion scan is a nuclear scan so named because it studies both airflow (ventilation) and blood flow (perfusion) in the lungs. The initials V-Q are used in mathematical equations that calculate airflow and blood flow. The test is used primarily to help diagnose a blood clot in the lungs, called a pulmonary embolus.
Today, ventilation-perfusion scans are rarely performed because a chest CT scan is a much more accurate diagnostic test for detecting a pulmonary embolus.
How do I prepare for the test?
About one hour before the test, a technician places an IV in your arm. A slightly radioactive version of the mineral technetium mixed with liquid protein is injected through the IV to identify areas of the lung that have reduced blood flow.
What happens when the test is performed?
The test is performed in the radiology department of a hospital or in an outpatient facility. You are asked to put on a hospital gown. Once you are ready, multiple pictures of your chest are taken from different angles, using a special camera that detects the radionuclide. For half of these pictures, you are asked to breathe from a tube that has a mixture of air, oxygen, and a slightly radioactive version of a gas called xenon, which can be detected by the camera, and which measures airflow in different parts of the lung. For the other half of the pictures, the camera tracks the injected radionuclide to determine blood flow in different parts of the lung. A blood clot is suspected in areas of the lung that have good airflow but poor blood flow. Except for the minor discomfort of having the IV placed, the test is painless. It usually takes less than one hour.
What risks are there from the test?
Many people worry when they hear that the liquid and gas used in this test are slightly radioactive. In truth, the radioactivity you are exposed to in this test is so small that there are no side effects or complications, unless you are pregnant.
Must I do anything special after the test is over?
No.
How long is it before the result of the test is known?
The results are usually available within a few hours, because the test is done primarily when you are suspected of having a potentially life-threatening condition (pulmonary embolus). The Second test is An arterial blood gas (ABG) test measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood from an artery. This test is used to check how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.
As blood passes through your lungs, oxygen moves into the blood while carbon dioxide moves out of the blood into the lungs. An ABG test uses blood drawn from an artery, where the oxygen and carbon dioxide levels can be measured before they enter body tissues. An ABG measures:
• Partial pressure of oxygen (PaO2). This measures the pressure of oxygen dissolved in the blood and how well oxygen is able to move from the airspace of the lungs into the blood.
• Partial pressure of carbon dioxide (PaCO2). This measures how much carbon dioxide is dissolved in the blood and how well carbon dioxide is able to move out of the body.
• pH. The pH measures hydrogen ions (H+) in blood. The pH of blood is usually between 7.35 and 7.45. A pH of less than 7.0 is called acid and a pH greater than 7.0 is called basic (alkaline). So blood is slightly basic.
• Bicarbonate (HCO3). Bicarbonate is a chemical (buffer) that keeps the pH of blood from becoming too acidic or too basic.
• Oxygen content (O2CT) and oxygen saturation (O2Sat) values. O2 content measures the amount of oxygen in the blood. Oxygen saturation measures how much of the hemoglobin in the red blood cells is carrying oxygen (O2).
Blood for an ABG test is taken from an artery. Most other blood tests are done on a sample of blood taken from a vein, after the blood has already passed through the body's tissues where the oxygen is used up and carbon dioxide is produced.
Why It Is Done
An arterial blood gas (ABG) test is done to:
• Check for severe breathing problems and lung diseases, such as asthma, cystic fibrosis, or chronic obstructive pulmonary disease (COPD).
• See how well treatment for lung diseases is working.
• Find out if you need extra oxygen or help with breathing (mechanical ventilation).
• Find out if you are receiving the right amount of oxygen when you are using oxygen in the hospital.
• Measure the acid-base level in the blood of people who have heart failure, kidney failure, uncontrolled diabetes, sleep disorders, severe infections, or after a drug overdose.
How To Prepare
Tell your doctor if you:
• Have had bleeding problems or take blood thinners, such as aspirin or warfarin (Coumadin).
• Are taking any medicines.
• Are allergic to any medicines, such as those used to numb the skin (anesthetics).
If you are on oxygen therapy, the oxygen may be turned off for 20 minutes before the blood test. This is called a "room air" test. If you cannot breathe without the oxygen. The last test is What is cardiac catheterization? This is a procedure to examine blood flow to the heart and test how well the heart is pumping. A doctor inserts a thin plastic tube (catheter) (KATH'eh-ter) into an artery or vein in the arm or leg. From there it can be advanced into the chambers of the heart or into the coronary arteries.
This test can measure blood pressure within the heart and how much oxygen is in the blood. It's also used to get information about the pumping ability of the heart muscle. Catheters are also used to inject dye into the coronary arteries. This is called coronary angiography (an"je-OG'rah-fe) or coronary arteriography (ar-te"re-OG'rah-fe). Catheters with a balloon on the tip are used in the procedure called coronary angioplasty (commonly referred to as percutaneous coronary intervention [PCI]). Catheterization of the heart may also be done on infants and children to examine for congenital (kon-JEN'ih-tal) heart defects. And then on Sept 27,2010 I will be see Dr Lee at 1:30pm to see if i pass all the test.
