Introduction Physical activity is reduced at COPD exacerbation but there is little information on the quantification of this activity. Activity can be assessed using walking tests or questionnaires or with expensive accelerometer based monitoring devices that require regular clinic visits to download data. Both approaches are not well suited to prospectively capturing activity during an exacerbation in a large observational cohort as patients will need to be monitored continuously in order to capture the prodrome and early stages of these events. The aim of this study was to determine whether step-counts measured by a pedometer (Yamax Digi-Walker SW-200) were sufficiently correlated with other measures of physical activity prospectively, to show that the device can be used in COPD patients.
Methods Patients with COPD (n=33) wore the pedometer and a SenseWear Armband (BodyMedia, Inc.) during a 6-min walk test (6MWT). FEV1, height, age and gender were recorded prior to the test. The pedometer was worn on a belt on the left-hand side and a SenseWear device on the left arm. Patients performed a 6MWT according to ATS protocols when stable and while having an exacerbation.
Results The 33 patients had a mean age (±SD) 71.5 (±6.2) and FEV1 % predicted 48.2% (±13.2); 26 were men. The patients walked a mean 415 (±117) metres in 6 min, taking 587 (±132) steps and expending 26.3 calories (±9.8). Twenty-four patients completed the 6MWT when stable and five completed it during an exacerbation. Four patients were assessed at both baseline and exacerbation. Abstract P44 figure 1 shows that there was a strong correlation between steps counted by the pedometer and distance covered [r=0.82; p<0.001], and little change in this relationship between the stable and exacerbation state. The correlation was significant between steps and calories [r=0.67; p<0.001].
Conclusion Step count correlates well with 6 min walking distance and energy expenditure in COPD patients. Thus pedometers may be a useful way to prospectively monitor and quantify physical activity during COPD exacerbations in a large observational cohort.
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