Lung function decline in COPD

Abstract

The landmark study of Fletcher and Peto on the natural history of tobacco smoke-related chronic airflow obstruction suggested that decline in the forced expiratory volume in the first second (FEV(1)) in chronic obstructive pulmonary disease (COPD) is slow at the beginning, becoming faster with more advanced disease. The present authors reviewed spirometric data of COPD patients included in the placebo arms of recent clinical trials to assess the lung function decline of each stage, defined according to the severity of airflow obstruction as proposed by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines. In large COPD populations the mean rate of FEV(1) decline in GOLD stages II and III is between 47 and 79 mL/year and 56 and 59 mL/year, respectively, and lower than 35 mL/year in GOLD stage IV. Few data on FEV(1) decline are available for GOLD stage I. Hence, the loss of lung function, assessed as expiratory airflow reduction, seems more accelerated and therefore more relevant in the initial phases of COPD. To have an impact on the natural history of COPD, it is logical to look at the effects of treatment in the earlier stages.

Keywords: FEV1; chronic obstructive pulmonary disease; decline; forced expiratory volume in 1 second.

Figure 1

Modified version of Fletcher and Peto’s graph showing the decline in the forced expiratory volume in the first second (FEV₁).

Figure 2

Range of average rate of decline in the forced expiratory volume in the first second (FEV₁) of chronic obstructive pulmonary disease patients according to initial severity of airflow reduction. Notes: The dashed segment of the line highlights any stage or part of it where consistent information is still lacking; control data from the UPLIFT (understanding Potential Long-term Impacts on Function with Tiotropium) study were not considered in the analysis. Abbreviation: yr, year.