Longitudinal change of FEV ₁ and inspiratory capacity: Clinical implication and relevance to exacerbation risk in patients with COPD

Background and objective: FEV ₁ is the gold standard for assessment of COPD. We compared efficacy of FEV ₁ , inspiratory capacity (IC), and IC to total lung capacity (TLC) ratio in the evaluation of COPD and their association with exacerbation. Methods: We analyzed the association of dyspnea severity, quality of life status, and lung function with lung function measurements and exacerbation risk in 982 patients enrolled in the Korea COPD Subgroup Registry and Subtype Research study. Exacerbation and longitudinal lung function change were evaluated in 3 years’ follow-up. Results: The FEV ₁ , IC, and IC to TLC ratio showed comparable negative correlations with dyspnea severity and quality of life status, and positive correlation with exercise capacity. In patients with >2 events/year, annual rate of change in FEV ₁ and IC tended to decline more rapidly in those with FEV ₁ <50% than in those with FEV ₁ >50% (-14.46±19.40 mL/year vs 12.29±9.24 mL/year, P=0.213;-4.75±17.28 mL/year vs-78.05±34.16 mL/year, P=0.056 for FEV ₁ and IC, respectively), without significance. Conclusion: Longitudinal changes in IC and FEV ₁ were not significantly associated with exacerbation risk.