Objective: To characterize the presence, extent, and patterns of dynamic hyperinflation (DH) during treadmill exercise testing in patients with moderate to severe COPD. Methods: This was a cross-sectional study involving 30 non-hypoxemic patients (FEV1= 43 ± 14% of predicted) who were submitted to a cardiopulmonary exercise test on a treadmill at a constant speed (70-80% of maximum speed) to the tolerance limit (Tlim). Serial inspiratory capacity (IC) maneuvers were used in order to assess DH. Results: Of the 30 patients studied, 19 (63.3%) presented with DH (DH+ group), having greater pulmonary function impairment at rest than did those without DH (DH− group). None of the variables studied correlated with exercise tolerance in the DH− group, whereas Tlim, IC, and perception of dyspnea during exercise did so correlate in the DH+ group (p < 0.05). In the DH+ group, 7 and 12 patients, respectively, presented with a progressive and a stable pattern of DH (ΔICTlim,2min = −0.28 ± 0.11 L vs. 0.04 ± 0.10 L; p < 0.01). Patients with a progressive pattern of DH presented with higher perception of dyspnea/Tlim rate and lower exercise tolerance than did those with a stable pattern (354 ± 118 s and 465 ± 178 s, respectively; p < 0.05). Conclusions: The presence of DH is not a universal phenomenon during walking in COPD patients, even in those with moderate to severe airflow limitation. In the patients who presented DH, a progressive pattern of DH had a greater impact on exercise tolerance than did a stable pattern of DH.

Keywords: Pulmonary disease, chronic obstructive; Exercise; Exercise test; Inspiratory capacity.

Objective: To investigate the modulatory effects that dynamic hyperinflation (DH), defined as a reduction in inspiratory capacity (IC), has on exercise tolerance after bronchodilator in patients with COPD. Methods: An experimental, randomized study involving 30 COPD patients without severe hypoxemia. At baseline, the patients underwent clinical assessment, spirometry, and incremental cardiopulmonary exercise testing (CPET). On two subsequent visits, the patients were randomized to receive a combination of inhaled fenoterol/ipratropium or placebo. All patients then underwent spirometry and submaximal CPET at constant speed up to the limit of tolerance (Tlim). The patients who showed ΔIC(peak-rest) < 0 were considered to present with DH (DH+). Results: In this sample, 21 patients (70%) had DH. The DH+ patients had higher airflow obstruction and lower Tlim than did the patients without DH (DH−). Despite equivalent improvement in FEV1 after bronchodilator, the DH− group showed higher ΔIC(bronchodilator-placebo) at rest in relation to the DH+ group (p < 0.05). However, this was not found in relation to ΔIC at peak exercise between DH+ and DH− groups (0.19 ± 0.17 L vs. 0.17 ± 0.15 L, p > 0.05). In addition, both groups showed similar improvements in Tlim after bronchodilator (median [interquartile range]: 22% [3-60%] vs. 10% [3-53%]; p > 0.05). Conclusions: Improvement in TLim was associated with an increase in IC at rest after bronchodilator in HD− patients with COPD. However, even without that improvement, COPD patients can present with greater exercise tolerance after bronchodilator provided that they develop DH during exercise.

Keywords: Pulmonary disease, chronic obstructive; Bronchodilator agents; Exercise test; Exercise tolerance; Inspiratory capacity.