Figure 1

Lung volumes and capacities in normal subjects and in COPD patients. A) Lung volumes and capacities in healthy subject: EELV, end-expiratory lung volume, ERV, expiratory reserve volume; FRC, functional residual capacity; IC, inspiratory capacity; IRV, inspiratory reserve volume; RV, residual volume; TLC, total lung capacity; VC, vital capacity; VT, tidal volume. B) Progressive increasing in static lung hyperinflation in relation to severity of COPD; arrow 1 indicates the threshold of dyspnea onset; arrow 2 indicates the limit of dyspnea tolerance. Modified from [19].