Resarch topics

Objective Pain Evaluation

Medical engineering group

We proposed a novel pain intensity assessment method based on changes in peripheral arterial stiffness index β, which responds to peripheral sympathetic nerve activity. β is calculated from continuous arterial pressure and plethysmogram per beat based on a log-linearized peripheral vascular viscoelastic model. The validity of the proposed method was examined by comparing the estimated normalized arterial stiffness index βn and the subjective pain assessment index (numeric rating scale: NRS) as an index of the pain intensity when electrical stimulation is applied to the skin of healthy subjects. The results show that the maximum amplitude of the current (Imax) has a linear correlation with βn (R2 = 0.77, p < 0.05). In addition, Imax and βn are correlated with the sigmoid-transformed NRS (Imax vs NRS: R2 = 0.91, p < 0.01; βn vs NRS: R2 = 0.92, p < 0.01). Therefore, we concluded that the proposed method can objectively evaluate the intensity of pain.


1.Quantification of Sympathetic Nervous Activity Based on Log-linearized Peripheral Arterial Viscoelastic Model and its Application to Objective Assessment of Pain During Electrocutaneous Stimulation (in Japanese)
Hiroki Matsubara, Hiroki Hirano, Harutoyo Hirano, Genki Matsuoka, Yuichi Kurita, Teiji Ukawa, Ryuji Nakamura, Noboru Saeki, Masao Yoshizumi, Masashi Kawamoto, and Toshio Tsuji
Transactions of the Society of Instrument and Control Engineers, Vol. 51, No. 9, pp. 627-633, 2015.

2.Assessment of Pain with Mechanical Nociceptive Stimuli by the Change of Arterial Wall Impedance
Abdugheni KUTLUK, Harutoyo HIRANO, Ryuji NAKAMURA, Noboru SAEKI, Masao YOSHIZUMI, Masashi KAWAMOTO, Murat HAMIT, and Toshio TSUJI
The 2012 5th International Conference on BioMedical Engineering and Informatics (BMEI 2012), pp. 315-318, Chongqing, China, October 16-18, 2012.