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

Abstract

BackgroundTo 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 Findings79 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/SignificanceCOPD 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.

Gait analysis in patients with chronic obstructive pulmonary disease: a systematic review

“…The sample size of patients with COPD ranged from 14 to 196 (mean age range: 64-75 years). Three papers [22,23,25] relied on traditional optical motion capture combined with force platforms to collect full-body three-dimensional kinematics and kinetics (joint angles, moments and powers); in the remaining papers, spatiotemporal parameters and dependent variables were obtained by means of electronic walkways [12,26], video analysis [24] or inertial units [27]. All studies required participants to walk at their self-selected walking speed, either over ground (6MWT) or on a treadmill.…”

“…McCamley et al [25] and Yentes et al [22] did not find significant differences between groups, since they matched patients and controls in terms of walking speed, either a-priori or by covariate analysis. In addition, patients with COPD generally tend to reduce their stride (and step) length and cadence [12,23,26,27].…”

“…Variability measures were provided by two papers [23,27]. When evaluated as standard deviation, step width variability was reduced in patients with COPD, and step time variability was increased [23].…”

“…When evaluated as standard deviation, step width variability was reduced in patients with COPD, and step time variability was increased [23]. A lower autocorrelation coefficient, meaning an increased variability over time, was computed on step width [27].…”

“…In particular, they measured an increased peak ankle power absorption at mid-stance and a lack of increase in peak ankle dorsiflexion moment in fatigued conditions with respect to controls. Annegarn et al [27] combined accelerometer data into a unique synthetic variable, called 'walking intensity', that was computed from the integral of the modulus of the output of an accelerometer placed at the trunk level. Walking intensity was lower in COPD patients than in controls, and proved to be strongly correlated with the distance covered in the 6MWT, and moderately correlated with FEV1.…”