Use of Accelerometry to Monitor Physical Activity in Critically Ill Subjects: A Systematic Review

Medical management of critically ill patients often incorporates prolonged bed rest, which, in combination with the underlying illness, results in global muscle weakness and atrophy. Recent evidence has demonstrated improvements in clinical and functional outcomes when exercise and physical activity are incorporated early in the management of ICU patients. Accurate monitoring of ICU patients' physical activity is essential for proper prescription and escalation of activity levels. Accelerometry is a technique used to measure physical activity and has been validated in several ambulatory populations. However, its use in critically ill, hospitalized patients with poor functional mobility is limited. In this review, we focus on the few studies assessing the use of accelerometry to measure physical activity in the care of mechanically ventilated adult ICU patients. The selected literature demonstrates that accelerometry correlates well with direct observation in reporting frequency and duration of various types of physical activity (rolling, sitting up, transferring, walking), but cannot differentiate various intensities of activity or whether movements are voluntary or involuntary with respect to effort. Thus, although accelerometry may serve as a useful adjunct in reporting temporality of physical activity in critically ill patients, other objective information may be needed to accurately record frequency, duration, and intensity of activity in this population.