Pain detection with bioimpedance methodology from 3-dimensional exploration of nociception in a postoperative observational trial

Although the measurement of dielectric properties of the skin is a long-known tool for assessing the changes caused by nociception, the frequency modulated response has not been considered yet. However, for a rigorous characterization of the biological tissue during noxious stimulation, the bioimpedance needs to be analyzed over time as well as over frequency. The 3-dimensional analysis of nociception, including bioimpedance, time, and frequency changes, is provided by ANSPEC-PRO device. The objective of this observational trial is the validation of the new pain monitor, named as ANSPEC-PRO. After ethics committee approval and informed consent, 26 patients were monitored during the postoperative recovery period: 13 patients with the in-house developed prototype ANSPEC-PRO and 13 with the commercial device MEDSTORM. At every 7 min, the pain intensity was measured using the index of Anspec-pro or Medstorm and the 0-10 numeric rating scale (NRS), pre-surgery for 14 min and post-anesthesia for 140 min. Non-significant differences were reported for specificity-sensitivity analysis between ANSPEC-PRO (AUC = 0.49) and MEDSTORM (AUC = 0.52) measured indexes. A statistically significant positive linear relationship was observed between Anspec-pro index and NRS (r(2) = 0.15, p < 0.01). Hence, we have obtained a validation of the prototype Anspec-pro which performs equally well as the commercial device under similar conditions

Bioimpedance sensor and methodology for acute pain monitoring

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

A fractional order impedance individualised model of nociceptor stimulation

This paper introduces a mathematical model and methodology for detecting and analysing nociceptor stimulation effects by means of non-invasive evaluation of the skin impedance in the hand palm. The derivation of the model is based on multi-scale physiological stages during perception of pain in awake individuals and contains elements of fractional calculus. The result is a lumped fractional order impedance model, to be used in a personalised way, i.e. per individual and not per population distribution data. A measurement device and a protocol have been determined in collaboration with Ghent University Hospital pain specialists. The experiments support our claim that changes occur in skin impedance during stimulation, i.e. when perceived as pain in one awake healthy volunteer. Following this proof of concept study, the model enables simulation of how nociceptor stimulation enters the systemic process of pain, for further analysis and development within the regulatory loops of pain management practices. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved

Electrical resistance of the skin

Function, structure, and electric resistance measurement of ski

The Effects of Transcutaneous Electrical Neurostimulation on Analgesia and Peripheral Perfusion

Peripheral arterial occlusive disease (PAOD) affects 8 to 12 million Americans over the age of 50. As the disease progresses, arterial occlusions arising from atherosclerotic lesions inhibit normal metabolic vasodilation in the peripheries, resulting in limb ischemia and claudication. Pharmacological and surgical treatments currently used to treat both the hemodynamic and pain symptoms associated with PAOD can involve adverse and potentially life-threatening side effects. Thus, there is a need for additional innovative therapies for PAOD. Neurostimulation has a known analgesic effect on both acute and chronic pain. Although the exact mechanisms remain under investigation, local vascular tone may be modulated by neurostimulation in addition to pain modulation. The Gate Control Theory proposes that electrical activation of mechanoreceptive afferent somatosensory nerves, specifically Aβ fibers, inhibits pain signaling to the brain by activating an inhibitory interneuron in the dorsal horn of the spinal cord which dampens signaling from afferent, C type peripheral nociceptor nerves. Interestingly, Aβ fiber activation may also inhibit norepinephrine release from sympathetic nerve terminals on efferent neurons by activating α-2 adrenergic receptors along the same dermatome, resulting in localized vasodilation in both limbs. Ultimately, electrical stimulation may decrease mean blood pressure and increase local blood flow. The focus of this study was to optimize protocols and perform a small scale clinical study to investigate hemodynamic and analgesic responses to neurostimulation during acute ischemia. We hypothesized that ganglial transcutaneous electrical neurostimulation (TENS) and interferential current (IFC) treatments would decrease pain perception and vascular resistance in the periphery in young, healthy subjects. We further hypothesized that IFC may have a greater hyperemic and analgesic effect on acute ischemia than TENS as its current waveform may be more efficient at overcoming skin impedance. Interestingly, we found trends suggesting that TENS and IFC may increase vascular resistance (VR) and have no noticeable analgesic effect, though TENS may have a slightly lower increase in VR associated with an increase in pain. Further work characterizing the hemodynamic effects of different stimulus waveforms is needed to inform future research into possible neuromodulation therapies for ischemic disease

Paresthesia thresholds in spinal cord stimulation: a comparison of theoretical results with clinical data

The potential distributions produced in the spinal cord and surrounding tissues by dorsal epidural stimulation at the midcervical, midthoracic, and low thoracic levels were calculated with the use of a volume conductor model. Stimulus thresholds of myelinated dorsal column fibers and dorsal root fibers were calculated at each level in models in which the thickness of the dorsal cerebrospinal fluid (CSF) layer was varied. Calculated stimulus thresholds were compared with paresthesia thresholds obtained from measurements at the corresponding spinal levels in patients. The influences of the CSF layer thickness, the contact separation in bipolar stimulation and the laterality of the electrodes on the calculated thresholds were in general agreement with the clinical dat

Theoretical aspects of metal-electrolyte interfaces Final report

Skin surface electrode and electrochemical cell characteristics for human bioelectric response determination

Impacts of selected stimulation patterns on the perception threshold in electrocutaneous stimulation

<p>Abstract</p> <p>Background</p> <p>Consistency is one of the most important concerns to convey stable artificially induced sensory feedback. However, the constancy of perceived sensations cannot be guaranteed, as the artificially evoked sensation is a function of the interaction of stimulation parameters. The hypothesis of this study is that the selected stimulation parameters in multi-electrode cutaneous stimulation have significant impacts on the perception threshold.</p> <p>Methods</p> <p>The investigated parameters included the stimulated location, the number of active electrodes, the number of pulses, and the interleaved time between a pair of electrodes. Biphasic, rectangular pulses were applied via five surface electrodes placed on the forearm of 12 healthy subjects.</p> <p>Results</p> <p>Our main findings were: 1) the perception thresholds at the five stimulated locations were significantly different (p < 0.0001), 2) dual-channel simultaneous stimulation lowered the perception thresholds and led to smaller variance in perception thresholds compared to single-channel stimulation, 3) the perception threshold was inversely related to the number of pulses, and 4) the perception threshold increased with increasing interleaved time when the interleaved time between two electrodes was below 500 μs.</p> <p>Conclusions</p> <p>To maintain a consistent perception threshold, our findings indicate that dual-channel simultaneous stimulation with at least five pulses should be used, and that the interleaved time between two electrodes should be longer than 500 μs. We believe that these findings have implications for design of reliable sensory feedback codes.</p