Obstructive Lung Disease

Obstructive lung disease is any condition that narrows the airways so air cannot be breathed out quickly, such as COPD, emphysema, chronic bronchitis or asthma. On breathing tests it shows up as a low ratio of FEV1 to FVC. It is the main contrast to restrictive lung disease, the pattern typical of asbestosis.

Origin

The distinction between obstructive and restrictive patterns grew out of spirometry, which measures how much and how fast a person can exhale. It became standard in pulmonary function testing in the mid-twentieth century and remains the basic way breathing tests are read.

Significance in Asbestos Context

Asbestosis stiffens the lungs and shrinks lung volumes, which is a restrictive pattern: total lung capacity and FVC fall, but the FEV1/FVC ratio stays normal or high. Obstructive disease does the opposite, and in asbestos cases it is most often caused by smoking. Many exposed workers were also smokers, so their tests can show a mixed pattern. This is why defense experts often argue that breathlessness comes from smoking-related obstruction rather than asbestos. Trust pulmonary function criteria for asbestosis look for a restrictive pattern, and some trusts also require that the FEV1/FVC ratio not be too low, so that the reduced lung volumes are not explained by obstruction. A full test with lung volumes and diffusing capacity, not just spirometry, gives the clearest picture. Some studies suggest asbestos exposure can also contribute to airflow obstruction, but that link is less settled than its link to restriction.

Example Sentence

Her spirometry showed an FEV1/FVC ratio of 58 percent, an obstructive pattern from emphysema, while her lung volumes were also mildly reduced.

Related Terms

Restrictive Lung Disease, COPD, Emphysema, Spirometry, FEV1/FVC Ratio, Pulmonary Function Test (PFT), Total Lung Capacity (TLC), Smoking Defense

Notes

• Ask for a full pulmonary function test, including lung volumes and DLCO, not only spirometry.
• Keep every breathing test report; changes over time matter.
• Give your doctors and lawyer an honest smoking history; it is needed to read the tests correctly.