Changes in Lung Volumes with Spirometric Disease Progression in COPD.
Academic Article
Overview
abstract
BACKGROUND: Abnormal lung volumes representing air trapping identify the subset of smokers with preserved spirometry who develop spirometric COPD and adverse outcomes. However, how lung volumes evolve in early COPD as airflow obstruction develops remains unclear. METHODS: To establish how lung volumes change with development of spirometric COPD, we examined lung volumes from the pulmonary function data (seated posture) available in the U.S. Department of Veterans Affairs electronic health records (n=71,356) and lung volumes measured by computed tomography (supine posture) available from COPDGene (n=7,969) and SPIROMICS (n=2,552) cohorts, and studied their cross-sectional distributions and longitudinal changes across airflow obstruction spectrum. Patients with preserved ratio impaired spirometry (PRISm) were excluded from this analysis. RESULTS: Lung volumes from all three cohorts showed similar patterns of distributions and longitudinal changes with worsening airflow obstruction. The distributions for total lung capacity (TLC), vital capacity (VC), and inspiratory capacity (IC) and their patterns of change were nonlinear and included different phases. When stratified by airflow obstruction using GOLD stages, patients with GOLD-1 (mild) COPD had larger lung volumes (TLC, VC, IC) compared to patients with GOLD-0 (smokers with preserved spirometry) or GOLD-2 (moderate) disease. In longitudinal follow-up of baseline GOLD-0 patients who progressed to spirometric COPD, those with initially higher TLC and VC developed mild obstruction (GOLD-1) while those with initially lower TLC and VC developed moderate obstruction (GOLD-2). CONCLUSIONS: In COPD, TLC and VC have biphasic distributions, change in nonlinear fashions as obstruction worsens, and could differentiate those GOLD-0 patients at risk for more rapid spirometric disease progression.
