[Dyspnea and inspiratory effort capacity in COPD]

The aim of this work was to study the relationship between dynamic hyperinflation and dyspnoea perception on exercise in patients with chronic obstructive pulmonary disease (COPD). Seven men and three women with COPD (mean FEV1 45.9 +/- 9.8% predicted) were studied. The upper end of the visual analogue scale was anchored on a preliminary test on a cycle ergometer (day 1). On the study day (day 2) the relationship between dyspnoea and ventilatory indices during high intensity exercise was evaluated, using within-subject linear regression analysis. On a repeat study (day 3), the addition of inspiratory capacity (IC) manoeuvres allowed to monitor the end expiratory lung volume. The highest degree of within-subject correlation was observed between dyspnoea and the tidal peak inspiratory flow (PIFT), as well without (median r2 = 0.920, day 2) as with (median r2 = 0.880, day 3) IC manoeuvres. At maximal exercise, IC decreased in 8 out of 10 subjects (delta IC range -150 to -900 ml). A negative relationship was found between delta IC and the rate of increase in dyspnoea on exercise, measured as the dyspnoea/PIFT slope (r = 0.844, p < 0.01). Our results suggest that dynamic hyperinflation on exercise observed in most patients with COPD allows these subjects to minimize the rate of increase in dyspnoea on exercise.