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Original Research

Open Access

Facial expression differences indicate pain improvement at the emergency department

  • Kuo-Cheng Wang1,5
  • Chen-June Seak2,5
  • Fu-Sheng Tsai3
  • Cheng-Yu Chien4
  • Chi-Chun Lee3
  • Chip-Jin Ng5
  • Bo-Cyuan Wang6,7
  • Yi-Ming Weng1,5,8

1Department of Emergency Medicine, Prehospital Care Division, Tao-Yuan General Hospital, Taoyuan, Taiwan

2Department of Emergency Medicine, New Taipei City Municipal Tucheng Hospital (Built and Operated by Chang Gung Medical Foundation), New Taipei, Taiwan

3Department of Electrical Engineering, National Tsing Hua University, Hsinchu, Taiwan

4Department of Emergency Medicine, Ton-Yen General Hospital, Hsinchu, Taiwan

5Department of Emergency Medicine, Chang Gung Memorial Hospital,and Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan

6Department of Nursing, New Taipei City Municipal Tucheng Hospital (Built and Operated by Chang Gung Medical Foundation), New Taipei, Taiwan

7School of Nursing, College of Nursing, Taipei Medical University, Taipei, Taiwan

8Faculty of Medicine, National Yang-Ming University, Taipei, Taiwan

DOI: 10.22514/sv.2020.16.0105 Vol.17,Issue 2,March 2021 pp.111-118

Published: 08 March 2021

*Corresponding Author(s): Yi-Ming Weng E-mail:


Purpose: Pain is a major symptom for patients to seek medical services, but limited evidence supports the applicability and usage of facial expressions as a pain measurement strategy in the emergency department (ED). In this study, we explored possible differences in facial expressions before and after pain management and compared these differences with those in a self-reported pain scale.

Methods: In this observational study, convenience sampling of patients admitted to the ED was conducted. Two video sessions of facial expressions were recorded for each participant, and participants rated their painon a self-reported numeric rating scale (NRS). A total of 25 facial parameters were extracted per frame. The main outcome measurements were the differences in facial parameters, and their correlation with changes in NRS scores was examined.

Results: This study included 163 participants. A stronger reduction in NRS scores was associated with differences in systolic blood pressure (sBPr = 0.247, P = 0.011) and the following changes in facial features: eye opening (left: r = -0.210, P = 0.007; right: r = -0.206, P = 0.008), eye aspect ratio (left: r = -0.382, P < 0.001; right: r = -0.305, P < 0.001), and head rotation angle (r = 0.218, P = 0.005). Pain improvement (a difference of ≥ 4 in NRS scores) was associated with differences in BP (sBP, odds ratio [OR] = 0.973, 95% confidence interval [CI]: 0.949-0.998, P = 0.034; dBP, OR = 1.078, 95% CI: 1.026-1.113, P = 0.003), eye aspect ratio (Left: β = 5.613, 95% CI: 2.234-14.104, P < 0.001; Right: β = 2.743, 95% CI: 1.395-5.391, P = 0.003), and nasolabial fold variation (β = 0.548, 95% CI: 0.306-0.982, P = 0.043), after adjustment for variables.

Conclusions: Intraindividual changes in facial expressions can be used to track clinically relevant differences in pain. Facial expressions alone cannot be used as a pain measurement strategy in the ED.


Pain; Pain measurement; Analogue pain scale; Facial expression; Facial recognition

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Kuo-Cheng Wang,Chen-June Seak,Fu-Sheng Tsai,Cheng-Yu Chien,Chi-Chun Lee,Chip-Jin Ng,Bo-Cyuan Wang,Yi-Ming Weng. Facial expression differences indicate pain improvement at the emergency department. Signa Vitae. 2021. 17(2);111-118.


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