Respiratory/Pulmonary Diagnostic Testing
Pulmonary Function Testing
Lung function tests (also called pulmonary function tests, or PFTs) check how well your lungs work. The tests determine how much air your lungs can hold, how quickly you can move air in and out of your lungs, and how well your lungs put oxygen into and remove carbon dioxide from your blood. The tests can diagnose lung dieases, measure the severity of lung problems, and check to see how well treatment for a lung disease is working.
Other tests, such as residual volume, gas diffusion tests, body plethysmography, inhalation challenge tests, and exercise stress test may also be done to determine lung function.
Spirometry is the first and most commonly done lung function test. It measures how much and how quickly you can move air out of your lungs. For this test, you breathe into a mouthpiece attached to a recording device called a spirometer. The information collected by the spirometer may be printed out on a chart called a spirogram.
6 Minute Walking Test
The six minute walk is used to test exercise tolerance in chronic respiratory disease and heart failure. The six-minute walk test (6MWT) measures the distance an individual is able to walk over a total of six minutes on a hard, flat surface. The goal is for the individual to walk as far as possible in six minutes. The individual is allowed to self-pace and rest as needed as they traverse back and forth along a marked walkway.
Arterial Blood Gas (ABG) Test
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): 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): 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.