SESSION TITLE: COPD Diagnosis and Evaluation Posters I
SESSION TYPE: Original Investigation Poster
PRESENTED ON: Wednesday, October 29, 2014 at 01:30 PM - 02:30 PM
PURPOSE: Measuring physical activity in COPD is desirable since physical inactivity is common and predicts increased health care utilization and mortality risk. While most studies have used motion detectors placed near the center of the body (such as a lateral position on the waist), a device worn on the wrist like a wrist watch would be far more convenient to the patient during long-term measurement. Unfortunately, validation studies of movement output that correspond to energy expenditure are generally available only for devices worn on the waist, not the wrist.
METHODS: After Institutional Review Board approval, we asked 20 patients to wear ActiGraph GT3X+ triaxial accelerometer devices simultaneously on the waist and ipsilateral wrist for at least 24 awake hours. We considered the output from the waist site to be the “gold standard”. Vector Magnitude Units (VMU, the minute-by-minute sum of movements in 3 planes) from the device worn at the waist that corresponded to VMU > 3000 from the device on the wrist were determined. We had previously used this threshold to separate higher from lower intensity physical activity in COPD.
RESULTS: The sample mean age was 70 ± 10 years and the FEV1 was 45 ± 18%. Activity data from over 40,000 minutes were compared using mixed modeling. Physical activity intensity above this threshold was present in16% of the recorded minutes. Mean VMU from the wrist device above the 3000 threshold were 4953 (95% confidence interval (CI), 4850 to 5055), while corresponding VMU from the waist device were 951 (95% CI, 916 to 986). Using a proprietary software equation developed for the waist location, activity intensity above this threshold corresponded to 1.66 metabolic units (METs) (95% CI, 1.55 to 1.77).
CONCLUSIONS: Movements detected from an activity monitor worn on a wrist site are considerably higher than from a waist site.
CLINICAL IMPLICATIONS: Activity monitoring from a conveniently-worn wrist site can provide meaningful data providing the above differences in activity counts are taken into consideration.
DISCLOSURE: The following authors have nothing to disclose: Chinthaka Bulathsinghala, John Tejada, Richard Zuwallack
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