title: Evaluation of single-breath helium dilution total lung capacity in obstructive lung disease.
abstract: We examined the effect of obstructive lung disease on the single-breath helium dilution method of measuring total lung capacity (TLC). In test results of 79 patients, we found this dilution method underestimated the TLC determined by a radiographic method by a mean of 2.3% in normal subjects, 10.4% in patients with mild, 21.8% in those with moderate, and 38.0% in those with severe obstruction. The ratio of forced expiratory volume in one second to forced vital capacity was used to group the patients; the differences in the degree of underestimation of TLC between groups were significant (p less than 0.05). In addition, we found a strong correlation between the degree of underestimation of TLC by the helium method and the severity of obstruction when patients were considered as a continuous population. Using a regression equation based on this correlation, we derived a method for correcting the helium dilution TLC. This allows use of this test in patients whose obstructive disease would otherwise render it inaccurate.
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005541:Forced Expiratory Volume; D006371:Helium; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D008433:Mathematics; D008722:Methods; D008875:Middle Aged; D011859:Radiography; D012119:Respiration; D014109:Total Lung Capacity; D014797:Vital Capacity
chemical_list: D006371:Helium