@article {Vaz Fragosorespcare.05515, author = {Carlos A Vaz Fragoso and Hilary C Cain and Richard Casaburi and Patty J Lee and Lynne Iannone and Linda S Leo-Summers and Peter H Van Ness}, title = {Spirometry, Static Lung Volumes, and Diffusing Capacity}, elocation-id = {respcare.05515}, year = {2017}, doi = {10.4187/respcare.05515}, publisher = {Respiratory Care}, abstract = {BACKGROUND: Spirometric Z-scores from the Global Lung Initiative (GLI) rigorously account for age-related changes in lung function and are thus age-appropriate when establishing spirometric impairments, including a restrictive pattern and air-flow obstruction. However, GLI-defined spirometric impairments have not yet been evaluated regarding associations with static lung volumes (total lung capacity [TLC], functional residual capacity [FRC], and residual volume [RV]) and gas exchange (diffusing capacity).METHODS: We performed a retrospective review of pulmonary function tests in subjects >=40 y old (mean age 64.6 y), including pre-bronchodilator measures for: spirometry (n = 2,586), static lung volumes by helium dilution with inspiratory capacity maneuver (n = 2,586), and hemoglobin-adjusted single-breath diffusing capacity (n = 2,508). Using multivariable linear regression, adjusted least-squares means (adjLSMeans) were calculated for TLC, FRC, RV, and hemoglobin-adjusted single-breath diffusing capacity. The adjLSMeans were expressed with and without height-cubed standardization and stratified by GLI-defined spirometry, including normal (n = 1,251), restrictive pattern (n = 663), and air-flow obstruction (mild, [n = 128]; moderate, [n = 150]; and severe, [n = 394]).RESULTS: Relative to normal spirometry, restrictive-pattern had lower adjLSMeans for TLC, FRC, RV, and hemoglobin-adjusted single-breath diffusing capacity (P <= .001). Conversely, relative to normal spirometry, mild, moderate, and severe air-flow obstruction had higher adjLSMeans for FRC and RV (P \< .001). However, only mild and moderate air-flow obstruction had higher adjLSMeans for TLC (P \< .001), while only moderate and severe air-flow obstruction had higher adjLSMeans for RV/TLC (P \< .001) and lower adjLSMeans for hemoglobin-adjusted single-breath diffusing capacity (P \< .001). Notably, TLC (calculated as FRC + inspiratory capacity) was not increased in severe air-flow obstruction (P >= .11) because inspiratory capacity decreased with increasing air-flow obstruction (P \< .001), thus opposing the increased FRC (P \< .001). Finally, P values were similar whether adjLSMeans were height-cubed standardized.CONCLUSIONS: A GLI-defined spirometric restrictive pattern is strongly associated with a restrictive ventilatory defect (decreased TLC, FRC, and RV), while GLI-defined spirometric air-flow obstruction is strongly associated with hyperinflation (increased FRC) and air trapping (increased RV and RV/TLC). Both spirometric impairments were strongly associated with impaired gas exchange (decreased hemoglobin-adjusted single-breath diffusing capacity).}, issn = {0020-1324}, URL = {https://rc.rcjournal.com/content/early/2017/07/11/respcare.05515}, eprint = {https://rc.rcjournal.com/content/early/2017/07/11/respcare.05515.full.pdf}, journal = {Respiratory Care} }