Development of a Pain Evaluation System by Image Analysis of Facial Expression

Yoshikazu Maekawa, Takeshi Abe, Yoko Akiyama, and Shigehiro Nishijima


Facial expression, Pain, Image analysis


In the field of nursing care for the elderly, understanding their somatic sensations, such as pain, is very important for caregivers to be able to provide appropriate care. However, it is not always easy for caregivers to understand such somatic sensations of an elderly person with declining verbal function. Therefore, an objective evaluation method of pain intensity without verbal communication is required. In this study, a pain evaluation system was developed for use in a daily life where verbal communication is not possible. This system is noninvasive because the information corresponding to pain intensity is extracted from facial expressions. In order to digitize the facial expressions, images of faces were extracted from a video at a regular time interval and were analyzed sequentially. A pain stimulation test where healthy adult subjects dipped their hands into ice water was carried out. A strong correlation between pain face factor calculated from the facial expressions digitized by the system and sensory evaluation shown by a pain score, VAS value, was observed for young adults. It indicates the validity of this system for estimation of pain intensity.

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