Abstract
PURPOSE: Activity monitoring is considered a highly relevant outcome measure of respiratory rehabilitation. This study aimed to assess the usefulness of a new accelerometric method for characterization of walking activity during a 3-week inpatient rehabilitation program.
METHODS: After individual calibration of the accelerometer at different walking speeds, whole-day physical activity was recorded for 15 patients with chronic obstructive pulmonary disease on the first and the last days of the program, and for 10 healthy subjects. Data were expressed as percentage of time spent in inactivity, low level activity, and medium level activity, with the latter corresponding to usual walking speed.
RESULTS: The patients spent more time being inactive and less time walking than healthy subjects. At the end of the rehabilitation program, medium level activity had increased from 4% to 7% of total recording time. However, the change was not significant after periods of imposed exercise training were excluded. Walking activity increased to a greater degree among the patients with preserved limb muscle strength at entry to the program. Although health status scores improved, the changes did not correlate with the changes in walking activity.
CONCLUSION: The findings lead to the conclusion that this new accelerometric method provides detailed analysis of walking activity during respiratory rehabilitation and may represent an additional useful measure of outcome.
The life of patients with chronic obstructive pulmonary disease (COPD) is characterized by dyspnea, reduced exercise tolerance, inactivity, and social isolation. Respiratory rehabilitation with lower and upper limb muscle training is able in part to reverse this adverse evolution. 1-3 Outcome measures of respiratory rehabilitation usually include exercise tolerance, dyspnea, and questionnaires of health-related quality of life or health status. The level of spontaneous physical activity during daily living represents an index of functional status that is highly relevant for assessing the efficacy of rehabilitation.
Spontaneous physical activity can be assessed indirectly by questionnaires assessing health status 4-7 or daily activities specifically. 8-10 However, these questionnaires rely on the patient's perception and memory of daily functioning.
In contrast, movement detectors provide an objective measure of activity. Pedometers register each movement in the vertical axis as a single count. Movement counts were shown by 1-week recordings to be markedly lower for patients with COPD than for normal patients, and higher after the introduction of nocturnal mechanical ventilation for patients with respiratory failure. 11 The distance walked can be obtained by individual calibration of pedometers. 12 However, accelerometers measure the pattern and intensity of body movements more precisely. Because of the periodic acceleration and deceleration of gait, accelerometric methods appear to be particularly useful for quantifying walking activity. In a 6-minute walking test among patients with COPD, the accelerometer values correlated highly with the distance walked. 13 This method also was shown to detect periods of brisk walking among patients after their completion of a respiratory rehabilitation program. 14
Recently, a new accelerometric method was validated for assessing the daily walking practice. 15 On the basis of individual calibration, this method can estimate walking speed and duration, as well as the distribution of walking activity periods during the day. This study aimed to assess the usefulness of this new accelerometric method for characterizing the walking activity of patients with COPD during a rehabilitation program.