Abstract
The paper aims to revive the interest in bioimpedance analysis for pain studies in communicating and non-communicating (anesthetized) individuals for monitoring purpose. The plea for exploitation of full potential offered by the complex (bio)impedance measurement is emphasized through theoretical and experimental analysis. A non-invasive, low-cost reliable sensor to measure skin impedance is designed with off-the-shelf components. This is a second generation prototype for pain detection, quantification, and modeling, with the objective to be used in fully anesthetized patients undergoing surgery. The 2D and 3D time–frequency, multi-frequency evaluation of impedance data is based on broadly available signal processing tools. Furthermore, fractional-order impedance models are implied to provide an indication of change in tissue dynamics correlated with absence/presence of nociceptor stimulation. The unique features of the proposed sensor enhancements are described and illustrated here based on mechanical and thermal tests and further reinforced with previous studies from our first generation prototype.
Highlights
Human bioimpedance allows for the characterization of pain pathway by providing an electrical signature, whose time and frequency modulation informs on physiological and electrochemical phenomena
The location of the electrodes is decided for the palmar skin, because increased sweat gland activity, as well as generation of action potentials elicited by nociceptor membrane activation, reveal specific reactivity to psychological stimulation at palmar sites due to the greater density on these areas
As to the accuracy of the impedance values between the absence and presence of pain stimulus, sensors location should be fixed during the protocol and during clinical trials when compared among cohort groups
Summary
Human bioimpedance allows for the characterization of pain pathway by providing an electrical signature, whose time and frequency modulation informs on physiological and electrochemical phenomena. Skin impedance has been studied in multiple medical applications as an indicator for the functioning of the human body [1]. Bioimpedance is increasingly used to estimate the body composition [5,6] and to interpret the histological composition of different tissues [7]. Electrode recordings of sympathetic activity in skin nerves have been correlated with blood pressure and electrodermal activity (EDA) even from early times. EDA has a long history in psycho-physiological research, when observations showed a connection between skin electrical activity and mental stress, sweat glands, or pain [8]. Despite the common acceptation of its significance, the researchers’ interest for EDA in pathophysiological applications was revived recently [9]
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