Time-frequency varying tissue impedance properties from noxious stimulation protocols

Tissue impedance can be an evaluation factor for noxious stimulation in humans. It has been shown in several studies that bioimpedance can be used as a direct evaluation tool of pain. In this study, we evaluated the changes in perception of different stimuli (mechanical and thermal) applied to subjects in a safe laboratory environment. The measurements are performed with the in-house developed pain monitoring device ANSPEC-PRO, employing impedance evaluation as a function of time and frequency. In this paper the following hypotheses have been investigated: i) the time-frequency response is nonlinear and independent of stimuli type, ii) there are differences in energy between mechanical and thermal-induced pain as indicated by impedance changes.