Increasing the Resolution of Chronic Obstructive Pulmonary Disease Definition. Lessons from a Cohort with Remote but Extensive Exposure to Second-hand Tobacco Smoke

The Global Initiative for Chronic Obstructive Lung Disease criteria require a ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) (FEV1/FVC) of less than 0.70 for the diagnosis of chronic obstructive pulmonary disease, whereas other criteria emphasise a lower limit of normal approach. However, the use of Global Initiative for Chronic Obstructive Lung Disease (or lower limit of normal) criteria may result in classification of many smokers with respiratory morbidities as not having chronic obstructive pulmonary disease. Additional accuracy in defining chronic obstructive pulmonary disease could improve its management. To determine whether in a cohort with remote but long-standing exposure to second-hand tobacco smoke, air trapping as measured by ratio of residual volume to total lung capacity (RV/TLC) can identify a subgroup at risk for respiratory morbidity among those without chronic obstructive pulmonary disease defined by Global Initiative for Chronic Obstructive Lung Disease (or lower limit of normal) criteria. The authors performed an observational study of symptoms and lung function in a cohort of 256 subjects with a history of extensive occupational exposure to second-hand tobacco smoke but with preserved spirometry (FEV1/FVC and FEV1???lower limit of normal). Symptom prevalence were elicited by structured questionnaire and estimated the correlations between plethysmography-measured RV/TLC and spirometry-measured FEV1/FVC and FEV1. In subgroups of the cohort, the authors examined the association of maximum oxygen consumption ([Formula: see text]o2max) on exercise testing with RV/TLC (n?=?179), dynamic hyperinflation (exercise-induced changes in fraction of tidal breathing that is flow-limited on expiration [percentage of expiratory flow limitation, %EFL] and end-expiratory lung volume) (n?=?32), and radiographic gas trapping (percent low attenuation area in -860 to -950 Hounsfield units at end-expiration on computerized tomographic imaging of the lungs [%LAAexp-860to-950]) (n?=?23). The RV/TLC of the cohort was (median [interquartile range] {total range}) 91.6% [84.9-98.8%] {58.0-130.6%} of the predicted normal value and had wide variability over quintiles of FEV1/FVC and FEV1 (coefficients of variation, 13.6-27.8% and 11.1-32.9%, respectively). In age-, sex-, and height-adjusted models, respiratory symptoms were associated only with RV/TLC (P?=?0.011). Maximum oxygen consumption was inversely associated with RV/TLC (r2?=?0.47; P?=?0.017), rate of increase in %EFL (r2?=?0.44; P?=?0.008), and LAAexp-860to-950 (r2?=?0.27; P?=?0.037) even after adjustment for FEV1/FVC or FEV1. Receiver operating characteristic analysis for median of maximum oxygen consumption yielded an area under the curve of 0.63 for RV/TLC, compared with 0.53 for both FEV1/FVC and FEV1. Air trapping in those with exposure to second-hand tobacco smoke but without overt obstruction identifies a subgroup with increased risk for respiratory morbidity and may provide an additional dimension for definition of chronic obstructive pulmonary disease not captured by spirometry.

Authors: Arjomandi M, Zeng S, Blanc PD, Gold WM. ; Full Source: Annals of the American Thoracic Society. 2018 Apr;15(Supplement_2):S122-S123. doi: 10.1513/AnnalsATS.201707-518MG.

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