The use of helium-oxygen spirometry in occupational lung disease

One of the major problems in the study and management of occupational lung disease is to detect early impairment so that corrective measures can be taken before irreversible or more severe damage occurs. Unfortunately standard spirometric tests are not sensitive to functional impairment in small airways where the earliest abnormalities in many pulmonary diseases are thought to occur. A a result, several new tests have been devised in the last decade to study this so-called silent zone. Helium-oxygen spirometry, one such test, is safe, convenient, and can eaily be added to conventional air spirometry apparatus. Two studies using helium-oxygen and air spirometry done by the Appalachian Laboratory are presented. In the first, non-exposed controls were compared to flax workers with either low or high dust exposure. Both air and helium-oxygen flow volume curves showed decreased flow rates after a work-shift in the high exposure group but no change in controls. In the low-dust exposure group, only helium-oxygen spirometry detected decreased post-shift flow rates suggesting small airways disease. Coal miners were compared to controls in the second study. Subgroups of younger subjects, smokers, non-smokers, bronchitics, and non-bronchitics were also analyzed. In no case did helium-oxygen spirometry detect differences which were not present on routine air spirometry. It is concluded that further studies in this area are needed. At present, random screening with helium-oxygen spirometry for early occupational disease is not warranted, and this test remains an investigative tool.