Janneke Annegarn

Reproducibility of 6-minute walking test in patients with COPD

The reproducibility of the 6-min walking test (6MWT) needs to be more solidly studied. This study aimed to investigate the reproducibility of two 6MWTs performed on subsequent days in a large and representative sample of patients with chronic obstructive pulmonary disease (COPD), and to quantify the learning effect between the two tests, as well as its determinants. In a retrospective observational study, 1,514 patients with COPD performed two 6MWTs on subsequent days. Other measurements included body composition (dual X-ray absorptiometry), dyspnoea (Medical Research Council scale) and comorbidity (Charlson index). Although the 6MWT was reproducible (intraclass correlation coefficient = 0.93), patients walked farther in the second test (391 m, 95% CI 155–585 m versus 418 m, 95% CI 185–605 m; p<0.0001). On average, the second 6MWT increased by 27 m (or 7%), and 82% of patients improved in the second test. Determinants of improvement ≥42 m in the second test (upper limit of the clinically important change) were as follows: first 6MWT <350 m, Charlson index <2 and body mass index <30 kg·m−2 (OR 2.49, 0.76 and 0.60, respectively). The 6MWT was statistically reproducible in a representative sample of patients with COPD. However, the vast majority of patients improved significantly in the second test by an average learning effect of 27 m.

Differences in Walking Pattern during 6-Min Walk Test between Patients with COPD and Healthy Subjects

Background To date, detailed analyses of walking patterns using accelerometers during the 6-min walk test (6MWT) have not been performed in patients with chronic obstructive pulmonary disease (COPD). Therefore, it remains unclear whether and to what extent COPD patients have an altered walking pattern during the 6MWT compared to healthy elderly subjects. Methodology/Principal Findings 79 COPD patients and 24 healthy elderly subjects performed the 6MWT wearing an accelerometer attached to the trunk. The accelerometer features (walking intensity, cadence, and walking variability) and subject characteristics were assessed and compared between groups. Moreover, associations were sought with 6-min walk distance (6MWD) using multiple ordinary least squares (OLS) regression models. COPD patients walked with a significantly lower walking intensity, lower cadence and increased walking variability compared to healthy subjects. Walking intensity and height were the only two significant determinants of 6MWD in healthy subjects, explaining 85% of the variance in 6MWD. In COPD patients also age, cadence, walking variability measures and their interactions were included were significant determinants of 6MWD (total variance in 6MWD explained: 88%). Conclusions/Significance COPD patients have an altered walking pattern during 6MWT compared to healthy subjects. These differences in walking pattern partially explain the lower 6MWD in patients with COPD.

Objective Physical Activity Assessment in Patients With Chronic Organ Failure: A Validation Study of a New Single-Unit Activity Monitor

OBJECTIVE To validate a new activity monitor (CAM) in patients with chronic organ failure during 1 hour of unconstrained activity assessment. DESIGN A validation study in which participants wore a CAM (placed on the thigh) for 1 hour while they were videotaped. Participants were instructed to continue their normal daily routine at the rehabilitation center. SETTING CIRO+, A Centre of Expertise for Chronic Organ Failure. PARTICIPANTS Chronic organ failure patients (N=10) with a large range of functional exercise capacity. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURE Agreement in time spent on activities and postures according to video and CAM. RESULTS Cohen kappa coefficients for transient events resulted in an almost perfect agreement (0.85 ± 0.08) between the CAM and video. CONCLUSIONS The CAM is a promising single-sensor unobtrusive tool for providing accurate data on the type and duration of daily activities in the home environment of patients with chronic organ failure.

Characteristics of daily arm activities in patients with COPD

Arm activities are required for maintenance of self-care and independent living. This study aimed to investigate whether and to what extent arm activities of daily living (ADL) in chronic obstructive pulmonary disease (COPD) patients differ compared to healthy controls and the extent to which they perform arm ADL at a relatively higher upper limb muscle effort. Daily arm and leg activities were assessed using accelerometers in the home environment (COPD: n=21, healthy: n=24; part 1). The relative efforts of the trapezius, deltoid and biceps muscles were studied using electromyography during domestic arm ADL in a laboratory setting (COPD: n=17, healthy: n=15; part 2). After correction for walking time, the time spent on arm ADL was similar between COPD patients and healthy control subjects (p=0.52), while the intensity of arm activities was lower in COPD patients (p=0.041). In the laboratory setting, arm ADL were performed at a lower intensity by COPD patients, while the trapezius muscle effort was significantly higher during several arm ADL compared to healthy control subjects (p<0.05). COPD patients have a similar duration of arm ADL compared to healthy subjects after correction for walking time, but perform arm activities at a lower intensity. Moreover, patients perform some arm ADL at a relatively higher muscle effort. COPD patients perform daily arm activities less intensively than healthy subjects but require more muscle effort http://ow.ly/rSv25

Development and validation of a rule–based strength scaling method for musculoskeletal modelling

Rule–based strength scaling is an easy, cheap and relatively accurate technique to personalise musculoskeletal models. This paper presents a new strength scaling approach for musculoskeletal models and validates it by maximal voluntary contractions. A heterogeneous group of 63 healthy subjects performed maximal isometric knee extensions. A multiple linear regression analysis resulted in a best–fit rule–based strength scaling equation, with age, mass, height, gender, segment masses and segment lengths as predictors. A second strength scaling equation was obtained through multiple linear regression using backwards elimination, resulting in an equation consisting of only the significant predictors: age, body mass and gender. For validation purposes, 20 newly included healthy subjects performed a maximal isometric leg–press. The newly developed strength scaling technique taking all predictors into account resulted in the most accurate predictions of muscle activities compared to alternative strength scaling methods. These techniques personalise musculoskeletal models to a larger extend. However, some applications that require more detailed personalised models, imaging might be necessary to obtain more specific individual muscle characteristics.

Increase in walk distance is not enough evidence to add a walk to the 6-minute walk test

From the authors: H.S. Kulkarni and coworkers argue that a mean increase in 6-min walk distance (6MWD) of 27 m during a second 6-min walk test (6MWT) in 1,514 patients with chronic obstructive pulmonary disease (COPD) still does not provide enough evidence to consider performing two 6MWTs [1]. Even though we very much appreciate this correspondence, we disagree with the arguments and conclusions of H.S. Kulkarni and coworkers. H.S. Kulkarni and coworkers state that we implied that only the result of the second 6MWT should …