Veterans Administration, New York Harbor Health Care Services, Brooklyn, New York 11209, USA.
COPD. 2012 Apr;9(2):102-10. doi: 10.3109/15412555.2011.650238. Epub 2012 Mar 12.
Chronic Obstructive Pulmonary Disease (COPD) frequently has a significant impact on patients' everyday activity. Because of this, accurate measurement of daily activity is of particular interest. Although accelerometers are an objective means of measuring daily activity, these devices sense vibrations and erroneously score motor vehicle travel (MVT) as moderate physical activity. It is the objective of this study to develop a new method to analyze accelerometry data that would accurately classify MVT as non-acceleration, or sitting/standing. As sitting/standing has a different pattern of count-to-count variability than walking, we hypothesized that a rolling standard deviation (RSD), which is a measurement of volatility in the data, would more accurately classify periods of MVT than analysis based on activity counts alone. Twenty-two subjects with COPD were studied. A training set of 15% of the dataset was used to establish an RSD-threshold during MVT based on the upper 95%-confidence interval. The accuracy of the RSD thresholds were tested and presented as sensitivity, specificity and receiver operating curves. Results demonstrated high sensitivity and specificity suggesting that the RSD not only accurately classified MVT, but had a low rate of misclassification. The RSD analysis scored more MVT as sitting/standing than assessment by VMU alone. The accuracy of accelerometers to define the profile of daily activity in sedentary populations, such as those with COPD, is greatly improved.
慢性阻塞性肺疾病（COPD）常对患者的日常活动产生重大影响。因此，准确测量日常活动尤为重要。虽然加速度计是测量日常活动的一种客观手段，但这些设备感知振动，并错误地将机动车行驶（MVT）评为中度体力活动。本研究的目的是开发一种新的方法来分析加速度计数据，以准确地将 MVT 分类为非加速度，或坐/站。由于坐/站的计数到计数变化模式与行走不同，我们假设滚动标准差（RSD），即数据波动性的度量，将比仅基于活动计数的分析更准确地分类 MVT 期间。对 22 名 COPD 患者进行了研究。使用数据集的 15%作为训练集，根据 95%置信区间的上限，在 MVT 期间建立 RSD 阈值。测试并呈现 RSD 阈值的准确性，包括灵敏度、特异性和接收者操作曲线。结果表明灵敏度和特异性均较高，表明 RSD 不仅能准确分类 MVT，而且误分类率较低。RSD 分析将更多的 MVT 分类为坐/站，而不仅仅是 VMU 单独评估。加速度计在定义 COPD 等久坐人群的日常活动模式方面的准确性大大提高。
