Dynamic hyperinflation during treadmill exercise testing in patients with moderate to severe COPD

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 (1C) maneuvers were used in order to assess DH. Results: Of the 30 patients studied, 19 (63.3%) presented with OH (DH+ group), having greater pulmonary function impairment at rest than did those without UN (OH group). None of the variables studied correlated with exercise tolerance in the DH- group, whereas Tlim, 1C, 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 (Delta 1C(Tlim,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.