Changes in the endurance shuttle walk test in COPD patients with chronic respiratory failure after pulmonary rehabilitation: the minimal important difference obtained with anchor- and distribution-based method.

BACKGROUND: Although the endurance shuttle walk test (ESWT) has proven to be responsive to change in exercise capacity after pulmonary rehabilitation (PR) for COPD, the minimally important difference (MID) has not yet been established. We aimed to establish the MID of the ESWT in patients with severe COPD and chronic hypercapnic respiratory failure following PR. METHODS: Data were derived from a randomized controlled trial, investigating the value of noninvasive positive pressure ventilation added to PR. Fifty-five patients with stable COPD, GOLD stage IV, with chronic respiratory failure were included (mean (SD) FEV1 31.1 (12.0) % pred, age 62 (9) y). MID estimates of the ESWT in seconds, percentage and meters change were calculated with anchor based and distribution based methods. Six minute walking distance (6MWD), peak work rate on bicycle ergometry (Wpeak) and Chronic Respiratory Questionnaire (CRQ) were used as anchors and Cohen's effect size was used as distribution based method. RESULTS: The estimated MID of the ESWT with the different anchors ranged from 186-199 s, 76-82% and 154-164 m. Using the distribution based method the MID was 144 s, 61% and 137 m. CONCLUSIONS: Estimates of the MID for the ESWT after PR showed only small differences using different anchors in patients with COPD and chronic respiratory failure. Therefore we recommend using a range of 186-199 s, 76-82% or 154-164 m as MID of the ESWT in COPD patients with chronic respiratory failure. Further research in larger populations should elucidate whether this cut-off value is also valid in other COPD populations and with other interventions. TRIAL REGISTRATION: ClinicalTrials.Gov (ID NCT00135538).

Short- and long-term effects of a physical activity counselling programme in COPD: a randomized controlled trial.

BACKGROUND: We were interested in the effects of a physical activity (PA) counselling programme in three groups of COPD patients from general practice (primary care), outpatient clinic (secondary care) and pulmonary rehabilitation (PR). METHODS: In this randomized controlled trial 155 COPD patients, 102 males, median (IQR) age 62 (54-69) y, FEV1predicted 60 (40-75) % were assigned to a 12-weeks' physical activity counselling programme or usual care. Physical activity (pedometer (Yamax SW200) and metabolic equivalents), exercise capacity (6-min walking distance) and quality of life (Chronic Respiratory Questionnaire and Clinical COPD Questionnaire) were assessed at baseline, after three and 15 months. RESULTS: A significant difference between the counselling and usual care group in daily steps (803 steps, p = 0.001) and daily physical activity (2214 steps + equivalents, p = 0.001)) from 0 to 3 months was found in the total group, as well as in the outpatient (1816 steps, 2616 steps + equivalents, both p = 0.007) and PR (758 steps, 2151 steps + equivalents, both p = 0.03) subgroups. From 0 to 15 months no differences were found in physical activity. However, when patients with baseline physical activity>10,000 steps per day (n = 8), who are already sufficiently active, were excluded, a significant long-term effect of the counselling programme on daily physical activity existed in the total group (p = 0.02). Differences in exercise capacity and quality of life were found only from 0 to 3 months, in the outpatient subgroup. CONCLUSION: Our PA counselling programme effectively enhances PA level in COPD patients after three months. Sedentary patients at baseline still benefit after 15 months. ClinicalTrials.gov: registration number NCT00614796.

Functional and psychological variables both affect daily physical activity in COPD: a structural equations model.

BACKGROUND: Daily physical activity (DPA) level is reduced in patients with COPD. The aim of this study was to investigate the association of DPA with functional and psychological variables in these patients. METHODS: 155 COPD patients (102 males, median (IQR) age 62 years (54-69 years), predicted FEV1 60% (40-75%) were included. We assessed DPA (DigiWalker SW-200), functional capacity and psychological factors. RESULTS: DPA level was significantly associated with all functional capacity variables and two psychological variables (Perceived Physical Ability Subscale, depression subscale of the Hospital Anxiety and Depression Scale). The six-minute walking distance and St. George Respiratory Questionnaire activity score explained 37% of the variance of DPA in a regression analysis. A structural equations model revealed that psychological variables indirectly explained DPA through functional capacity variables. DPA was stronger associated with functional capacity variables and weaker with psychological variables in patients with lower functional status than in patients with higher functional status. CONCLUSIONS: Higher levels of DPA are associated with better functional capacity, but interestingly, DPA is also affected by psychological factors, though only indirectly, via functional capacity. The effect of specific treatment addressing psychological factors on DPA level and exercise tolerance needs further investigation. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, NCT00614796.

A better response in exercise capacity after pulmonary rehabilitation in more severe COPD patients.

PURPOSE: Pulmonary rehabilitation (PR) has positive effects on exercise capacity in Chronic Obstructive Pulmonary Disease (COPD). However, not all COPD patients benefit from PR to the same extent. We investigated whether there is a patient profile, which is associated with the improvement in endurance exercise capacity. METHODS: In this observational study, we included 102 COPD patients who followed PR (age 60 ± 10 (mean ± SD) years, FEV(1)%predicted 44 ± 16%, 54 men). Lung function, maximal incremental cycle testing (Wpeak, VO(2)peak, Δlactate), quadriceps force and incremental and endurance shuttle walk test (ISWT/ESWT) were performed at the start of PR. The ESWT was repeated after 7 weeks of PR. RESULTS: Mean change in ESWT (ΔESWT) was 100 ± 154%. Four variables showed a statistically significant negative correlation with ΔESWT: FEV(1)%pred. (ρ = -0.20), Wpeak (ρ = -0.24), Δlactate (ρ = -0.33) and incremental shuttle walk test (ISWT) (ρ = -0.31). A cluster analysis identified two patient profiles: A profile with high ΔESWT, TLC and RV and low FEV(1), VO(2)peak, quadriceps force, Δlactate, HR(peak)%pred. and ISWT distance and a profile with low ΔESWT, TLC and RV and high FEV(1), VO(2)peak, quadriceps force, Δlactate, HR(peak)%pred. and ISWT distance. CONCLUSIONS: Single variables from lung function or exercise testing at baseline have limited predictive value for response to exercise training. However, patients with worse disease status (i.e. a combination of lower FEV(1), more hyperinflation, lower exercise capacity and worse quadriceps force) improve more in endurance exercise capacity.