3. Spirometric Patterns of Abnormal Lung Function Flashcards
What are three examples of obstructive pulmonary disease?
Three examples of obstructive disease are asthma, chronic bronchitis, and
emphysema.
In general, how does obstructive pulmonary disease affect lung function?
In general, obstructive diseases affect lung function by inhibiting airflow, especially on exhalation. In other words, people suffering from an obstructive disease can inhale a normal amount of air, but when they try to exhale forcefully, airflow is reduced due to decreased elastic recoil and, or, increased airway resistance.
How is the degree of airway obstruction measured in spirometry?
During a forced vital capacity (FVC) maneuver, the worker inhales maximally and then forcefully exhales the air over a period of time. However, the amount of air that can be exhaled in one second (FEV1) is reduced. The FEV1 is one indication of the degree of airway obstruction.
What is the FEV1/FVC ratio?
The FEV1 can be expressed as a percentage of the FVC. That is, the amount of air expired in one second is compared to the total amount of air expired after a 6–12 second period. This is expressed as a percentage.
Describe the characteristics of the FEV1/FVC% in obstructive disease.
In obstructive lung disease, the FEV1/FVC% is reduced. In general, a percentage of less than 70 is considered abnormal. A reduced FEV1/FVC ratio indicates that the individual has difficulty exhaling air quickly due to obstructive problems.
For example, an individual suffering from obstructive disease could exhibit the following:
Example:
FEV1 = 2.5 L of air
FVC = 4.2Lofair
FEV1%/FVC = 2.5 L/4.2 x 100
= 59.5%
This is less than 70% of the FVC and would need further investigation.
What are two examples of restrictive lung disease?
Two examples of restrictive disease are asbestosis and silicosis. Patterns of restrictive disease can also result from skeletal disorders such as kyphoscoliosis. Hypersensitivity pneumonitis and granulomatous disease also show restrictive patterns on spirometric tests.
In general, how do restrictive lung diseases affect lung function?
With restrictive lung diseases, the presence of fibrotic tissue causes decreased compliance and increased recoil.
How is the degree of restrictive disease measured in spirometry?
In restrictive lung diseases, the lungs cannot expand as fully as they should. Therefore, the FVC is reduced. In fact, if the restriction is severe enough, the FEV1 will be reduced as well.
Describe the characteristics of the FEV1/FVC% in restrictive disease.
In classical cases of restrictive disease, there is no airway obstruction. Therefore, the FEV1/FVC% remains normal. In other words, although the individual is only able to inhale and exhale a reduced amount of air, he or she is able to expel at least 70% of that air in one second.
What does a mixed pattern of disorder mean?
Mixed pattern disorders show elements of both obstructive and restrictive disease. For example, workers who suffer from asbestosis may also smoke, which can result in chronic bronchitis.
How might a severe obstructive condition influence the spirometric test interpretation?
With severe airway obstruction, there is often air trapping and hyperinflation. As a result, the FVC can be reduced. This decreased FVC may or may not indicate associated restrictive disease. Further in-depth tests are required.
The vital capacity (VC) is the maximal volume of air exhaled from the point of maximal inspiration. In spirometry, this can be tested without measuring the flow of air over time. Individuals with severe obstructive disease, given enough time, can exhale all the air from a maximal inspiration; however, when the FVC maneuver is completed within 6–12 seconds, the FVC may be lower than the VC because air has been trapped.
