  Critical care patients experience varying levels of pain during their stay in
the intensive care unit, often requiring administration of analgesics and
sedation. Such medications generally exacerbate the already sedentary physical
activity profiles of critical care patients, contributing to delayed recovery.
Thus, it is important not only to minimize pain levels, but also to optimize
analgesic strategies in order to maximize mobility and activity of ICU
patients. Currently, we lack an understanding of the relation between pain and
physical activity on a granular level. In this study, we examined the
relationship between nurse assessed pain scores and physical activity as
measured using a wearable accelerometer device. We found that average, standard
deviation, and maximum physical activity counts are significantly higher before
high pain reports compared to before low pain reports during both daytime and
nighttime, while percentage of time spent immobile was not significantly
different between the two pain report groups. Clusters detected among patients
using extracted physical activity features were significant in adjusted
logistic regression analysis for prediction of pain report group.
