Mechanisms of dyspnea during lung hyperinflation in chronic obstructive pulmonary disease

During exercise and exacerbations in COPD, acute increases in end-expiratory lung volume (EELV) with reciprocal decreases in inspiratory capacity (IC) give rise to dyspnea. We hypothesized that acute increases in EELV above the respiratory system's relaxation volume would induce dyspnea only if they were associated with mechanical restriction, i.e., an increased end-inspiratory lung volume (EILV) or reduced inspiratory reserve volume (IRV).; Stable patients with COPD (n = 13; FEV_1.0 = 42 ± 3% predicted; mean ± SEM) completed pulmonary function tests, a symptom-limited cycle exercise test and then breathed on a circuit that induced mechanical hyperinflation (HI) to correspond with IC levels attained during exercise.; The sensory responses to incremental mechanical HI were compared between normal subjects and patients with COPD at a similar ΔIC (isoΔIC).; Within the COPD group, measurements during mechanical HI were compared with exercise induced dynamic hyperinflation measurements at isoΔIC. (Abstract shortened by UMI.)...