How is bronchiolitis obliterans diagnosed? There are several diagnostic tools available to diagnose bronchiolitis obliterans. Spirometry is a test that evaluates lung function. Patients with bronchiolitis obliterans often have spirometry findings of fixed airways obstruction. Some patients also show restriction on spirometry which means that the lungs have decreased ability to expand. Additional tests include chest x-rays which are often normal, but may show hyperinflation (too much air trapped in the lungs). Another imaging test, high resolution computerized tomography scans (CT or CAT scans) may also show airtrapping and thickening of the airway walls. If a biopsy or tissue sample of the lungs is performed, narrowing or complete obstruction of the small airways may be seen when the tissue is examined with a microscope.1,2,3 What causes bronchiolitis obliterans? Bronchiolitis obliterans has been diagnosed in employees with occupational exposures to certain flavorings or certain irritant gasses such as ammonia, chlorine or sulfur dioxide. People who have had organ transplants or who have connective tissue disorders such as rheumatoid arthritis and lupus can develop bronchiolitis obliterans. Some respiratory infections caused by viruses/bacteria and certain medications are also associated with the development of bronchiolitis obliterans. Although many diseases or occupational exposures are associated with bronchiolitis obliterans, it is actually a rare disease. Diacetyl: Diacetyl (also called 2,3-butanedione), is a chemical that has been used to impart a butter-like flavor to food products, including popcorn. This chemical has been used as a marker of exposure to flavoring vapors in investigations evaluating lung disease in microwave popcorn manufacturing facilities. Acetoin (also called acetyl methyl carbinol), 2,3-pentanedione, 2,3 hexanedione and 2,3 heptanedione are all structurally related to diacetyl and have been suggested as possible substitutes for diacetyl. https://www.osha.gov/SLTC/flavoringlung/index.html - ref1di. Animal studies of exposure to butter flavoring vapors, including diacetyl, have shown airway injury in rats after acute inhalation of these flavorings.1,2 These studies demonstrated that butter flavoring vapors are capable of causing severe airway injury in laboratory animals, but the causal relationship between diacetyl exposure and development of bronchiolitis obliterans has not been firmly established. Research continues on diacetyl and other flavoring chemicals to evaluate the relationship of exposure to butter flavorings and adverse health effects, including lung disease. See more from topic source: https://www.osha.gov/html/a-z-index.html