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COPD is a progressive disease characterized by airflow obstruction or limitation. Emphysema is characterized by loss of elasticity of the lung tissue, destruction of structures supporting the alveoli and of capillaries feeding the alveoli. Both have symptoms that include shortness of breath, among other respiratory troubles. If you are a COPD or Emphysema sufferer, join...
Obstructive versus Restrictive Lung Diseases: Understanding the Differences
By Deborah Leader, RN,
When comparing the differences between obstructive and restrictive lung diseases, spirometry testing plays an important diagnostic role. Since each disease is characterized by a unique, physiologic pattern, careful interpretation of spirometry results helps doctors differentiate between the two conditions. Once the pattern is recognized, the right diagnosis should follow, but only after taking into consideration a patient's history, physical examination and additional diagnostic studies.
The following guide takes you on a journey through each disorder, then provides a wealth of information about what's really important when rendering and interpreting a spirometry test:
What Characterizes an Obstructive Lung Disease?
When a person has difficulty expelling all the air from her lungs, she's said to have an obstructive lung disease. An obstructive pattern exists when air moves out of the lungs at a slower rate than that of a healthy person. This occurs because inflammation and swelling (secondary to long-term, cumulative exposure to airway irritants) cause the airways to become narrow and blocked, making it difficult to completely rid the lungs of air. This leaves an abnormally high volume of air in the lungs after a full exhalation, which is referred to as "increased residual volume." In obstructive lung defects, increased residual volume leads to air getting trapped in, and hyperinflation of, the lungs two changes in the lungs that may contribute to worsening symptoms.
The following lung diseases are categorized as obstructive:
COPD (mainly a combination of emphysema and chronic bronchitis)
Chronic bronchitis
Asthma
Bronchiectasis
Bronchiolitis
What Characterizes a Restrictive Lung Disease?
Restrictive lung diseases are characterized by reduced total lung capacity (TLC). TLC represents the amount of air present in the lungs after taking the deepest breath possible. When a restrictive pattern is present, the lungs are "restricted" from fully expanding, making it difficult for a person to take a full breath. Measuring TLC is of critical importance to the diagnosis of restrictive lung disease because it confirms the presence of a true restriction, as well as quantifying the degree of that restriction. Restrictive lung diseases are categorized as intrinsic, extrinsic or neurological.
Intrinsic Restrictive Lung Disorders
Intrinsic, as it applies to lung disorders, refers to that which is inherent to the lungs themselves. Take a look at some common, intrinsic restrictive lung disorders:
Sarcoidosis
Pneumonia
Tuberculosis
Pneumonectomy
Extrinsic Restrictive Lung Diseases
Extrinsic, as it applies to lung disease, refers to that which originates from outside the anatomical boundaries of the lungs. The following lists several examples of extrinsic restrictive lung disorders:
Scoliosis
Kyphosis
Pleural effusion
Tumors
Ascites
Pleurisy
Rib fractures
Neurological Restrictive Lung Diseases
Restrictive lung diseases can also stem from neurological causes, including:
Paralysis of the diaphragm
Myasthenia gravis
Muscular dystrophy
Amyotrophic Lateral Sclerosis (ALS or Lou Gehrig's Disease)
Test Values Important to Spirometry Interpretation
Spirometry measures the rate of lung volume changes during forced breathing maneuvers. There are several values measured during spirometry that are critically important when diagnosing and distinguishing between obstructive and restrictive lung diseases. Following are the most critical:
Forced vital capacity (FVC) The FVC maneuver begins with the patient taking as deep a breath as possible, and then exhaling as forcibly, and for as long, as possible. Because lung capacity is reduced in both obstructive and restrictive diseases, the FVC measure alone does not diagnose either disorder.
Forced Expiratory Volume in One Second (FEV1) This value represents the total amount of air that can be forcibly exhaled in the first second of the FVC maneuver. Healthy individuals generally expel about 75% to 85% of their FVC in the first second of the test. The FEV1 is decreased in obstructive lung diseases and normal or decreased in restrictive lung diseases, although to a lesser degree than in obstructive disorders.
Ratio of FEV1 to FVC The ratio of FEV1 to FVC is referred to as FEV1/FVC, %FEV1 or FEV1%. It is indicative of the percentage of the total FVC expelled from the lungs during the first second of a forced exhalation. This ratio is decreased in obstructive lung disorders and normal or increased in restrictive lung disorders.
Total lung capacity and residual volume Lung volumes are critical to the diagnosis of restrictive lung disease. When a patient exhales as forcibly and for as long as he can, there will still be some air remaining in the lungs. The remaining amount represents the residual volume. When you add the residual volume plus the forced vital capacity together, their sum equals the total lung capacity (TLC). TLC is normal or increased in obstructive defects, and decreased in restrictive defects. TLC and residual volume are not measured by spirometry. Rather, their values are obtained through additional testing, including a test called body plethysmography.
Factors That Influence Spirometry
When patients undergo spirometry testing, especially if their results aren't favorable, they often ask if there was something they did or didn't do that may have influenced their test results. Indeed, there are certain factors that are associated with inaccurate spirometry results, the most common of which are listed below:
Inaccurate Demographic Data Individual spirometry test results are compared to results that are based on normal, predicted values. Predicted values are determined in population studies using subjects with normal lung function. Each patient will have her own set of predicted values based on demographic data from someone of the same age, height, weight and sex (and sometimes ethnicity). If for some reason a patient gives inaccurate demographic data, or demographic data is incorrectly entered by the technician, test results will be affected. A good doctor will review this information for accuracy before interpreting the test.
Acceptability After spirometry is performed, test results must be evaluated for acceptability and reproducibility (see below). Generally, the FVC maneuver is acceptable if the patient has made a good effort, a factor that's predetermined using specific criteria. If the patient is ill, or something else impairs his effort to forcibly inhale or exhale during the test, the results won't be accurate and will therefore be unacceptable.
Reproducibility The spirometry test should be repeated a minimum of three times. In order to meet reproducibility criteria, all three FEV1 measurements, and all three FVC measurements, must be within 200 milliliters (ml) of each other. The test with the greatest FEV1 and FVC represent the patient's test results for that particular test. If any one of these conditions isn't met, the test has failed to meet reproducibility criteria.
What Causes Results to be Inaccurate or Not Reproducible?
If test results aren't accurate or reproducible, the test won't reflect the patient's true, underlying lung impairment. The following includes a few of the most common reasons that this might occur:
Failing to provide sufficient effort (many times due to illness)
Not understanding test instructions due to either a language or cognitive barrier, or a hearing deficit.
Having pain that worsens with each maneuver, which ultimately affects effort
5-Step Approach to Spirometry Interpretation
Although your doctor is the best person to talk to about your spirometry results and the only one who can diagnose you with either an obstructive or a restrictive lung disease, there are several methods available that point clinicians in the right direction. The following is just one of many approaches
you can find the chart here: http://copd.about.com/od/copdbasics/a/Obstructive-Versus-Restrictive-Lung-Disease.htm
Step 1: Begin by looking at the forced vital capacity (FVC) to determine if it's within a normal range.
Step 2: Next, look at the forced expiratory volume in one second (FEV1) to see if it's within normal limits.
Step 3: If the FVC and the FEV1 are both normal, stop at this step the spirometry test is normal.
Step 4: If the FVC and/or the FEV1 are decreased, there is a strong possibility of lung disease.
Step 5: If Step 4 suggests the presence of lung disease, look closely at the %predicted for FEV1/FVC. If %predicted for FEV1/FVC is 69% or less (< 0.70 according to the Global Initiative for Obstructive Lung Disease), an obstructive lung disease is highly likely. A value of 85% or greater is suggestive of restrictive lung disease.
Meeting the Bronchodilator Challenge
Spirometry test results almost always include measurements obtained from both before and after administration of a bronchodilator. This is called a bronchodilator challenge. A bronchodilator challenge tells doctors the degree of broncho-constriction present and how well (or how poorly) a patient responds to a bronchodilator.
What constitutes as improvement varies from clinic to clinic, but the American Thoracic Society (ATS) defines it, in both COPD and asthma, as having an increase in post-bronchodilator FEV1 of at least 12% from baseline and of at least 200 milliliters. A significant bronchodilator response is favorable to both obstructive and restrictive lung diseases, indicating a positive response to treatment and in some cases, a better prognosis.
How is Disease Severity Determined?
There are several approaches to determining disease severity in both obstructive and restrictive lung diseases. Whichever method is used, FEV1 as a percentage of the predicted FEV1, quantifies the severity of obstruction in obstructive lung diseases. Similarly, forced vital capacity (FVC) or total lung capacity (TLC), as a percentage of the predicted FVC or TLC, quantifies the degree of restriction present in restrictive lung diseases.
NOTE: Remember, a variety of systems are used to interpret pulmonary function tests and determine the severity of disease. The information included in this article is just one approach. The article should only serve as a guide to help you better understand your test results. It is not meant to diagnose lung disease, nor should it replace sound medical advice from a health care professional. Please review your test results in detail with your primary care provider or your pulmunologist for further information.
http://copd.about.com/od/copdbasics/a/Obstructive-Versus-Restrictive-Lung-Disease.htm
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By Deborah Leader, RN,
When comparing the differences between obstructive and restrictive lung diseases, spirometry testing plays an important diagnostic role. Since each disease is characterized by a unique, physiologic pattern, careful interpretation of spirometry results helps doctors differentiate between the two conditions. Once the pattern is recognized, the right diagnosis should follow, but only after taking into consideration a patient's history, physical examination and additional diagnostic studies.
The following guide takes you on a journey through each disorder, then provides a wealth of information about what's really important when rendering and interpreting a spirometry test:
What Characterizes an Obstructive Lung Disease?
When a person has difficulty expelling all the air from her lungs, she's said to have an obstructive lung disease. An obstructive pattern exists when air moves out of the lungs at a slower rate than that of a healthy person. This occurs because inflammation and swelling (secondary to long-term, cumulative exposure to airway irritants) cause the airways to become narrow and blocked, making it difficult to completely rid the lungs of air. This leaves an abnormally high volume of air in the lungs after a full exhalation, which is referred to as "increased residual volume." In obstructive lung defects, increased residual volume leads to air getting trapped in, and hyperinflation of, the lungs two changes in the lungs that may contribute to worsening symptoms.
The following lung diseases are categorized as obstructive:
COPD (mainly a combination of emphysema and chronic bronchitis)
Chronic bronchitis
Asthma
Bronchiectasis
Bronchiolitis
What Characterizes a Restrictive Lung Disease?
Restrictive lung diseases are characterized by reduced total lung capacity (TLC). TLC represents the amount of air present in the lungs after taking the deepest breath possible. When a restrictive pattern is present, the lungs are "restricted" from fully expanding, making it difficult for a person to take a full breath. Measuring TLC is of critical importance to the diagnosis of restrictive lung disease because it confirms the presence of a true restriction, as well as quantifying the degree of that restriction. Restrictive lung diseases are categorized as intrinsic, extrinsic or neurological.
Intrinsic Restrictive Lung Disorders
Intrinsic, as it applies to lung disorders, refers to that which is inherent to the lungs themselves. Take a look at some common, intrinsic restrictive lung disorders:
Sarcoidosis
Pneumonia
Tuberculosis
Pneumonectomy
Extrinsic Restrictive Lung Diseases
Extrinsic, as it applies to lung disease, refers to that which originates from outside the anatomical boundaries of the lungs. The following lists several examples of extrinsic restrictive lung disorders:
Scoliosis
Kyphosis
Pleural effusion
Tumors
Ascites
Pleurisy
Rib fractures
Neurological Restrictive Lung Diseases
Restrictive lung diseases can also stem from neurological causes, including:
Paralysis of the diaphragm
Myasthenia gravis
Muscular dystrophy
Amyotrophic Lateral Sclerosis (ALS or Lou Gehrig's Disease)
Test Values Important to Spirometry Interpretation
Spirometry measures the rate of lung volume changes during forced breathing maneuvers. There are several values measured during spirometry that are critically important when diagnosing and distinguishing between obstructive and restrictive lung diseases. Following are the most critical:
Forced vital capacity (FVC) The FVC maneuver begins with the patient taking as deep a breath as possible, and then exhaling as forcibly, and for as long, as possible. Because lung capacity is reduced in both obstructive and restrictive diseases, the FVC measure alone does not diagnose either disorder.
Forced Expiratory Volume in One Second (FEV1) This value represents the total amount of air that can be forcibly exhaled in the first second of the FVC maneuver. Healthy individuals generally expel about 75% to 85% of their FVC in the first second of the test. The FEV1 is decreased in obstructive lung diseases and normal or decreased in restrictive lung diseases, although to a lesser degree than in obstructive disorders.
Ratio of FEV1 to FVC The ratio of FEV1 to FVC is referred to as FEV1/FVC, %FEV1 or FEV1%. It is indicative of the percentage of the total FVC expelled from the lungs during the first second of a forced exhalation. This ratio is decreased in obstructive lung disorders and normal or increased in restrictive lung disorders.
Total lung capacity and residual volume Lung volumes are critical to the diagnosis of restrictive lung disease. When a patient exhales as forcibly and for as long as he can, there will still be some air remaining in the lungs. The remaining amount represents the residual volume. When you add the residual volume plus the forced vital capacity together, their sum equals the total lung capacity (TLC). TLC is normal or increased in obstructive defects, and decreased in restrictive defects. TLC and residual volume are not measured by spirometry. Rather, their values are obtained through additional testing, including a test called body plethysmography.
Factors That Influence Spirometry
When patients undergo spirometry testing, especially if their results aren't favorable, they often ask if there was something they did or didn't do that may have influenced their test results. Indeed, there are certain factors that are associated with inaccurate spirometry results, the most common of which are listed below:
Inaccurate Demographic Data Individual spirometry test results are compared to results that are based on normal, predicted values. Predicted values are determined in population studies using subjects with normal lung function. Each patient will have her own set of predicted values based on demographic data from someone of the same age, height, weight and sex (and sometimes ethnicity). If for some reason a patient gives inaccurate demographic data, or demographic data is incorrectly entered by the technician, test results will be affected. A good doctor will review this information for accuracy before interpreting the test.
Acceptability After spirometry is performed, test results must be evaluated for acceptability and reproducibility (see below). Generally, the FVC maneuver is acceptable if the patient has made a good effort, a factor that's predetermined using specific criteria. If the patient is ill, or something else impairs his effort to forcibly inhale or exhale during the test, the results won't be accurate and will therefore be unacceptable.
Reproducibility The spirometry test should be repeated a minimum of three times. In order to meet reproducibility criteria, all three FEV1 measurements, and all three FVC measurements, must be within 200 milliliters (ml) of each other. The test with the greatest FEV1 and FVC represent the patient's test results for that particular test. If any one of these conditions isn't met, the test has failed to meet reproducibility criteria.
What Causes Results to be Inaccurate or Not Reproducible?
If test results aren't accurate or reproducible, the test won't reflect the patient's true, underlying lung impairment. The following includes a few of the most common reasons that this might occur:
Failing to provide sufficient effort (many times due to illness)
Not understanding test instructions due to either a language or cognitive barrier, or a hearing deficit.
Having pain that worsens with each maneuver, which ultimately affects effort
5-Step Approach to Spirometry Interpretation
Although your doctor is the best person to talk to about your spirometry results and the only one who can diagnose you with either an obstructive or a restrictive lung disease, there are several methods available that point clinicians in the right direction. The following is just one of many approaches
you can find the chart here: http://copd.about.com/od/copdbasics/a/Obstructive-Versus-Restrictive-Lung-Disease.htm
Step 1: Begin by looking at the forced vital capacity (FVC) to determine if it's within a normal range.
Step 2: Next, look at the forced expiratory volume in one second (FEV1) to see if it's within normal limits.
Step 3: If the FVC and the FEV1 are both normal, stop at this step the spirometry test is normal.
Step 4: If the FVC and/or the FEV1 are decreased, there is a strong possibility of lung disease.
Step 5: If Step 4 suggests the presence of lung disease, look closely at the %predicted for FEV1/FVC. If %predicted for FEV1/FVC is 69% or less (< 0.70 according to the Global Initiative for Obstructive Lung Disease), an obstructive lung disease is highly likely. A value of 85% or greater is suggestive of restrictive lung disease.
Meeting the Bronchodilator Challenge
Spirometry test results almost always include measurements obtained from both before and after administration of a bronchodilator. This is called a bronchodilator challenge. A bronchodilator challenge tells doctors the degree of broncho-constriction present and how well (or how poorly) a patient responds to a bronchodilator.
What constitutes as improvement varies from clinic to clinic, but the American Thoracic Society (ATS) defines it, in both COPD and asthma, as having an increase in post-bronchodilator FEV1 of at least 12% from baseline and of at least 200 milliliters. A significant bronchodilator response is favorable to both obstructive and restrictive lung diseases, indicating a positive response to treatment and in some cases, a better prognosis.
How is Disease Severity Determined?
There are several approaches to determining disease severity in both obstructive and restrictive lung diseases. Whichever method is used, FEV1 as a percentage of the predicted FEV1, quantifies the severity of obstruction in obstructive lung diseases. Similarly, forced vital capacity (FVC) or total lung capacity (TLC), as a percentage of the predicted FVC or TLC, quantifies the degree of restriction present in restrictive lung diseases.
NOTE: Remember, a variety of systems are used to interpret pulmonary function tests and determine the severity of disease. The information included in this article is just one approach. The article should only serve as a guide to help you better understand your test results. It is not meant to diagnose lung disease, nor should it replace sound medical advice from a health care professional. Please review your test results in detail with your primary care provider or your pulmunologist for further information.
http://copd.about.com/od/copdbasics/a/Obstructive-Versus-Restrictive-Lung-Disease.htm
I thought this might be helpful so someone here.
Love
Holly
ty :)