title: Validation of a compact motion sensor for the measurement of physical activity in patients with chronic obstructive pulmonary disease.
abstract: BACKGROUND
  The DynaPort Activity Monitor (DAM) has been reported to be useful to evaluate the activity in healthy subjects and patients with chronic obstructive pulmonary disease (COPD). However, it is difficult to estimate the activity of COPD patients using DAM, because its battery works only for several hours and sensors should be worn at two parts of the body. A newly developed compact, single-position triaxial accelerometer (Actimarker) can measure the activity for >1 month, but has not been validated for COPD patients.
  
  
  OBJECTIVE
  The validity of the Actimarker was evaluated in COPD patients.
  
  
  METHODS
  In study 1, the validity of the device was tested in 14 stable COPD patients by comparing it with DAM. In study 2, the influence of the weather on activity was examined. In study 3, the number of measurement days required to ensure repeatability was determined.
  
  
  RESULTS
  The durations of activity measured by the Actimarker and DAM were significantly correlated at intensity values ≥2.0, ≥2.5 and ≥3.0 METs. The duration of activity on rainy days was significantly shorter than that on non-rainy days. The values of intraclass correlation coefficients were >0.8 in 3-, 4- or 5-day measurements, and there was no systematic bias at any number of days or intensities with Bland-Altman plots.
  
  
  CONCLUSIONS
  The validity of the Actimarker was confirmed, and repeatability was obtained when the data from at least 3 non-rainy weekdays were analyzed. Actimarker appears to be useful as a simplified method to evaluate the physical activity of COPD patients.
authors.affiliation: Third Department of Internal Medicine, Wakayama Medical University, Wakayama, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Sugino
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Minakata
authors.forename: Masae
authors.initials: M
authors.lastname: Kanda
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Akamatsu
authors.forename: Akira
authors.initials: A
authors.lastname: Koarai
authors.forename: Tsunahiko
authors.initials: T
authors.lastname: Hirano
authors.forename: Hisatoshi
authors.initials: H
authors.lastname: Sugiura
authors.forename: Kazuto
authors.initials: K
authors.lastname: Matsunaga
authors.forename: Masakazu
authors.initials: M
authors.lastname: Ichinose
mesh_terms: D000054:Acceleration; D000368:Aged; D000886:Anthropometry; D015992:Body Mass Index; D015331:Cohort Studies; D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods; D009038:Motion; D009043:Motor Activity / Q000502:physiology*; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D013997:Time Factors