TAC may reflect the airway-related disease changes that accumulate in the "quiet" zone in early/mild COPD, indicating that TAC acquired with commercially available software across various CT platforms may be a biomarker to predict accelerated COPD progression.

BackgroundThe endurance shuttle walking test (ESWT) has shown good responsiveness to interventions in patients with chronic obstructive pulmonary disease (COPD). However, the minimal important difference (MID) for this test remains unknown, therefore limiting its interpretability. Methods Patients with COPD who completed two or more ESWTs following pulmonary rehabilitation (n¼132; forced expiratory volume in 1 s (FEV 1 ) 48622%) or bronchodilation (n¼69; FEV 1 50612%) rated their performance of the day in comparison with their previous performance on a 7-point scale ranging from À3 (large deterioration) to +3 (large improvement). The relationship between subjective perception of changes and objective changes in performance during the shuttle walk was evaluated.Results Following pulmonary rehabilitation, the anchorbased approach did not allow a valid estimation of the MID in the ESWT performance to be obtained. After bronchodilation, patient ratings of change correlated significantly with the difference in walking distance (r¼0.53, p<0.001) and endurance time (r¼0.55, p<0.001). For the pharmacotherapy data, regression analysis indicated that a 65 s (95% CI 45 to 85) change in endurance time and a 95 m (95% CI 60 to 115) change in walking distance were associated with a 1-point change in the rating of change scale. These changes represented 13e15% of the baseline values. Conclusions A change in endurance shuttle walking performance of 45e85 s (or 60e115 m) after bronchodilation is likely to be perceived by patients. This MID value may be specific to the intervention from which it was derived.

Few studies have shown that the endurance shuttle walking test (ESWT) is responsive to treatment in patients with chronic obstructive pulmonary disease (COPD). This exercise test needs to be further investigated because of its relevance for activity of daily living. The aim of the present study was to evaluate, in patients with COPD, the responsiveness of the ESWT in detecting improvement in walking performance after a single dose of salmeterol.In a randomised, double-blind, placebo-controlled crossover trial, 20 patients with COPD performed two ESWT at 80% of peak capacity 2.5 h after inhaling either a placebo or 50 mg of salmeterol. Cardiorespiratory parameters were monitored during each walking test. Inspiratory capacities and Borg ratings for dyspnoea were obtained every other minute throughout the tests.Compared with placebo, salmeterol produced a significant change in lung function and a significant improvement in walking performance (mean¡SD difference in time: 117¡20 s; difference in distance: 160¡277 m). At isotime (the latest exercise time that was reached on both ESWT), a significant reduction in dyspnoea was observed after bronchodilation.Bronchodilation with salmeterol reduced dyspnoea during walking and improved walking capacity in patients with chronic obstructive pulmonary disease. These findings provide further support for the use of the endurance shuttle walking test as an evaluative tool in chronic obstructive pulmonary disease.

Quadriceps muscle weakness and increased fatigability are well described in patients with chronic obstructive pulmonary disease (COPD). Whether these functional alterations also exist in distal leg muscles in patients with COPD is uncertain. Fifteen patients with COPD and 15 aged-matched healthy controls performed a 12-minute standardized treadmill exercise during which a fixed total expense of 40 Kcal was reached. The strength of i) dorsiflexors, ii) plantar flexors and iii) quadriceps was assessed at rest and after exercise using maximal voluntary contraction (MVC) and potentiated twitch force (Twpot). Resting MVC and Twpot were significantly lower in patients with COPD when compared with controls respectively for i) dorsiflexors (24.9 ± 8.4 vs. 31.2 ± 8.5 Nm, p < 0.05 and 4.3 ± 1.3 vs. 5.7 ± 1.8 Nm, p < 0.05), ii) plantar flexors (49.5 ± 11.8 vs. 62.1 ± 19.6 Nm, p < 0.05 and 10.8 ± 3.5 vs. 13.4 ± 2.7 Nm, p < 0.05), and iii) quadriceps muscles. There was a greater force loss in the distal leg muscles 15 minutes post-exercise in patients with COPD, while the strength of the quadriceps muscle remained stable in both groups. Patients with COPD had weaker dorsiflexor and plantar flexor muscles when compared to age-matched healthy controls. In addition, when exposed to the same absolute walking task, the fatigability of the distal leg muscles was higher in patients with COPD.