Validity of six activity monitors in chronic obstructive pulmonary disease: a comparison with indirect calorimetry.

Hans Van Remoortel,Santiago Giavedoni,Frederick Wilson,On Behalf Of Proactive Consortium ,Ioannis Vogiatzis,Chris Burtin,Zafeiris Louvaris,Thierry Troosters,Yogini Raste,Daniel Langer,Nicholas S Hopkinson,Roberto Rabinovich

doi:10.1371/journal.pone.0039198

Abstract

Reduced physical activity is an important feature of Chronic Obstructive Pulmonary Disease (COPD). Various activity monitors are available but their validity is poorly established. The aim was to evaluate the validity of six monitors in patients with COPD. We hypothesized triaxial monitors to be more valid compared to uniaxial monitors. Thirty-nine patients (age 68±7years, FEV1 54±18%predicted) performed a one-hour standardized activity protocol. Patients wore 6 monitors (Kenz Lifecorder (Kenz), Actiwatch, RT3, Actigraph GT3X (Actigraph), Dynaport MiniMod (MiniMod), and SenseWear Armband (SenseWear)) as well as a portable metabolic system (Oxycon Mobile). Validity was evaluated by correlation analysis between indirect calorimetry (VO2) and the monitor outputs: Metabolic Equivalent of Task [METs] (SenseWear, MiniMod), activity counts (Actiwatch), vector magnitude units (Actigraph, RT3) and arbitrary units (Kenz) over the whole protocol and slow versus fast walking. Minute-by-minute correlations were highest for the MiniMod (r = 0.82), Actigraph (r = 0.79), SenseWear (r = 0.73) and RT3 (r = 0.73). Over the whole protocol, the mean correlations were best for the SenseWear (r = 0.76), Kenz (r = 0.52), Actigraph (r = 0.49) and MiniMod (r = 0.45). The MiniMod (r = 0.94) and Actigraph (r = 0.88) performed better in detecting different walking speeds. The Dynaport MiniMod, Actigraph GT3X and SenseWear Armband (all triaxial monitors) are the most valid monitors during standardized physical activities. The Dynaport MiniMod and Actigraph GT3X discriminate best between different walking speeds.

Highlights

Chronic Obstructive Pulmonary Disease (COPD) is a chronic disease characterized by poorly reversible airflow limitation and destruction of lung parenchyma
The mean correlation between metabolic cost (METs) and activity monitor outputs over the whole protocol was, from highest to lowest; SenseWear (r = 0.76 [95% confidence interval 0.54–0.91]), Kenz (r = 0.52 [95% CI 0.27–0.73]), Actigraph (r = 0.49 [95% CI 0.28–0.64]), MiniMod (r = 0.45 [95% CI 0.21–0.61]), Actiwatch (r = 0.37 [95% CI 0.17–0.56]), all p,0.05 and RT3 (r = 0.35 [95% CI 20.04–0.48], p = 0.06) (Figure 3)
The validity of six commercially available activity monitors was investigated by comparing activity monitor outputs for each monitor to actual VO2 measured with indirect calorimetry

Summary

Introduction

Chronic Obstructive Pulmonary Disease (COPD) is a chronic disease characterized by poorly reversible airflow limitation and destruction of lung parenchyma. COPD is recognized as a systemic illness with significant extra-pulmonary features such as muscle wasting and weakness [1]. Physical inactivity is known to contribute to these extra-pulmonary features [2,3]. A recent systematic literature review showed that physical activity is reduced in patients with COPD [4]. Physical activity is defined as any bodily movement produced by the contraction of skeletal muscle that increases energy expenditure above a basal level [5]. There is increasing evidence that reduced physical activity worsens the prognosis of patients with COPD. Inactivity is a manifestation of disease severity in COPD, but is intrinsic to disease progression [6]

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Conclusion