How to read pulmonary function tests?

May 10, 2010

A pulmonary function test is one that is conducted to test the functioning of the breathing systems in your body. Humans inhale and exhale through the nose and mouth and this air is passed through to the lungs in the chest cavity. In the lungs, an air exchange takes place where oxygen from the air is absorbed into the blood and carbon dioxide from the blood is passed into the air. This contaminated air is then breathed out. There are several parameters that one can assess to judge the effectiveness of the breathing process in an individual. These parameters include the quantity of air exhaled, the components of the air, the speed at which a person absorbs gasses that are breathed in, and so on. These varied tests are performed by using a technique known as Spirometry. The results of such a test are plotted on a graph and then compared with the normal levels that are known to occur in healthy individuals. The test is conducted using the patient’s mouth and therefore the nose may be sealed using a nose clip.

There are several aspects to a pulmonary function test. Forced Vital Capacity is the total amount of air that is exhaled under force after the person has completed a full inhalation. The first second of this test is also measured. A ratio of the two is then calculated. A healthy individual will expel more than 75% of the total air in the first second whereas any blockage in the respiratory tract caused by inflammation or asthma will show a ratio less than 75%. The flow is also judged during the middle of the exhalation process to judge the speed of air flow. Again, this speed is dependent on whether the upper respiratory tract is blocked by inflammation or not. During this test, the Peak Expiration Volume is also measured which is the highest speed of airflow detected during the entire expiration process. Another test is conducted under normal breathing and this is called the Tidal Volume which measures the person’s air flow when the patient is idle, i.e. not panting or breathing heavily.

Finally, the Total Lung Capacity is measured. In patients who have conditions that fill their lungs with fluid, the TLC will be reduced. A final test may involve breathing in a gas that is harmful in large quantities. Carbon Monoxide is measured as it is breathed in and then breathed out to detect how much gas is being absorbed in the lungs.

Submitted by N on May 10, 2010 at 01:51

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