Determination of the minimal important difference for inspiratory muscle strength in people with severe and very severe COPD.

OBJECTIVE: Inspiratory muscle training is recommended for people with chronic obstructive pulmonary disease (COPD) with inspiratory muscle weakness. Clinical interpretation of changes in inspiratory muscle strength could be helped by the determination of cut-off values. The aim of this study was to estimate the minimal important difference for inspiratory muscle strength assessed with maximal inspiratory pressure (MIP) in people with COPD. DESIGN: Post hoc analysis of a randomized controlled trial (EMI2 study) including people with severe to very severe COPD undergoing a pulmonary rehabilitation program was conducted. The determination of the minimal important difference was realized using both anchor-based and distribution-based methods. SETTING: The study includes patients admitted to the rehabilitation program unit of the Centre Hospitalier des Pays de Morlaix (Morlaix, France) between March 5, 2014 and September 8, 2016. PARTICIPANTS: Seventy-three people with severe to very severe COPD (age 62.2 ± 8.0 years, forced expiratory volume in 1 s 36.4 ± 9.5% of theoretical) were analyzed. INTERVENTION: Patients followed a standardized pulmonary rehabilitation program 5 days a week for 4 weeks. The program included aerobic training, ground-based outdoor walking training, and strengthening of lower and upper limb muscles. MAIN MEASURES: At the end of the pulmonary rehabilitation program, MIP improved by 14.8 ± 14.9 cmH2O (p < 0.05). Regarding the anchor-based method, only the modified Medical Research Council was selected as an appropriate anchor. The receiver operating characteristic curve analysis reported a minimal important difference of 13.5 cmH2O (sensibility: 75% specificity: 67.5%). Using distribution-based methods, the estimate of minimal important difference was 7.9 cmH2O (standard error of measurement method) and 10.9 cmH2O (size effect method). RESULTS: The estimations proposed by this study ranged from 7.9 to 13.5 cmH2O. CONCLUSIONS: The measurement of minimal important difference is a simple tool for assessing the changes of inspiratory muscle strength during a pulmonary rehabilitation program. We propose a minimal important difference of 13.5 cmH2O for the improvement of MIP. Further studies are needed to confirm this estimation.ClinicalTrials.gov identifier: NCT02074813.

Effect of neuromuscular electrical stimulation on exercise capacity in patients with severe chronic obstructive pulmonary disease: A randomised controlled trial.

OBJECTIVE: To compare strengthening by neuromuscular electrical stimulation versus cycle ergometer training during a pulmonary rehabilitation program, in patients with severe to very severe chronic obstructive pulmonary disease. DESIGN: A prospective randomized controlled study. SETTING: Two inpatient pulmonary rehabilitation centers. SUBJECTS: Patients with severe to very severe chronic obstructive pulmonary disease and multidimensional index to predict risk of death ≥5, were randomly assigned to receive neuromuscular electrical stimulation or cycle ergometer training during pulmonary rehabilitation. MAIN MEASURES: The primary endpoint was the change in exercise capacity using 1-min sit-to-stand test Secondary endpoints were the changes in exercise capacity using 6-min walk test, quadriceps strength, quality of life and dyspnea. RESULTS: 102 patients were included. After 3 weeks, 47 patients in the neuromuscular electrical stimulation group, and 45 in the cycle ergometer training group were able to be analyzed. No significant difference was seen in the evolution of exercise capacity using 1-min sit-to-stand test (3.3 ± 3.8 and 2.6 ± 4.1) and 6-min walk test (37.8 ± 58.4 and 33.1 ± 46.7), in the evolution of quadriceps strength and endurance (9.2 ± 12.9 and 6.6 ± 16.1; 9.0 ± 13.2 and 6.2 ± 17.0), in the evolution of quality of life (St George's Respiratory Questionnaire: -11.3 ± 11.7 and -8.1 ± 11.6; COPD Assessment Test: -5.7 ± 7.1 and -4.7 ± 7.0), or in the evolution of dyspnea using Dyspnea 12 (-5.5 ± 10.2 and -5.9 ± 8.5) except using modified medical research council scale (95% confidence interval: 0.48 [0.05; 0.91], p = 0.027). CONCLUSION: We found no significant difference between the two programs on exercise capacity, quadriceps strength and quality of life.