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Pain Stimulator Bryan 1 Eckerle , 1 McFadden , 1 Platt , 2 Slyziuk , Katharine Adam Elizabeth Jennifer 1 3 Advisors: Paul King, Ph.D. and Stephen Bruehl, Ph.D. 1 Wells 1Vanderbilt University Department of Biomedical Engineering 2Vanderbilt University Department of Mechanical Engineering 3Vanderbilt University Medical Center Department of Anesthesiology SYSTEM SCHEMATIC Dr. Bruehl’s main objective is to understand endogenous pain regulatory mechanisms in humans, with particular interest in the relationship between blood pressure, acute pain sensitivity, and chronic pain. He is currently studying the effects of Yohimbine, a selective α-2 adrenergic receptor antagonist, to understand the role of the adrenergic system in regulation of pain pathways. He is using a device based on the original Forgione-Barber Finger Pressure Stimulator to stimulate C-fibers. The device has a fixed amount of weight attached to a lever with an unknown amount of pressure being applied to the dorsal surface of the second phalanx of the index finger. It is mounted on a table that does not allow for adjustments to accommodate variance in subject height or forearm length. Additionally, the system does not include an electronic output. The administrator asks the subject for a numerical pain rating on a scale from 0 to 100, anchored with “no pain” and “worst pain imaginable,” thus creating a numerical bias. Our objective is to create an adjustable, electronically integrated, and standardized acute pain stimulus to compare responses under placebo and under blockade of various receptors. EXAMPLE OF PREVIOUS DATA Circuit sensitivity = .6V/cm @ Vs=5V Potentiometer sensitivity = 1500Ω/cm USB DAQ NI 6009 PC Computer LabVIEW 7.1 ADDITIONAL EQUIPMENT PROJECT DELIVERABLES •National Instruments USB-6009 Data Acquisition Device •Modified version of Forgione-Barber Finger Pressure Stimulator •Mouser Electronics 60mm Linear 10k Taiwan Alpha Slide Potentiometer •National Instruments LabVIEW Version 7.1.1 PREVIOUS DEVICE Insert Cannula Assess Emotions (EAS) 5 Min. Seated Rest Plasma Sample Assess Baroreceptor Sensitivity (BRS) Drug or Placebo Infusion Over 10 Min. 20 Min. Seated Rest Assess EAS and Side Effects Plasma Sample Assess BRS: 5 Min. Seated Rest Insert Finger Adjust & Apply Pressure 15s Numerical Pain Rating 15s Numerical Pain Rating 15s 30 35 40 45 50 55 60 6.34 12.2 19.4 29.7 39.8 53.7 64.2 76.3 88.1 98.2 100 100 80 60 40 20 0 0 10 20 30 40 50 60 Time (sec) IMPROVED EXPERIMENTAL PROCEDURE 5 Min. Resting BP Assessment 5 Min. Rest 25 Design specifications were met so that the experiment is adjustable for subject variance, automated, and electronically integrated. The study is improved as a result. EXPERIMENTAL PROCEDURE 30 Min. Adaptation 20 CONCLUSION •Integrated system: device mounted to table, connected to sliding scale and software 15 Min. Seated Rest 15 IMPROVED DEVICE •Sliding scales to eliminate number bias Screening and Questionnaires 0 10 Pain Reading vs. Time Subject 008 Vibration, thermal and electrical stimuli were considered, but ultimately rejected in order to maintain pressure stimulus of C-fibers. A pneumatic pressure device was also considered, but rejected for the stable and reliable lever system already in place. •Vertically adjustable medical table 5 DEVICE APPROACHES CONSIDERED NO GRAPHICAL OUTPUT MANUAL DATA ENTRY NECESSARY RESULTS Time, sec Pain Level Potentiometer Circuits Contact Switch Circuit •Software for data acquisition Subject Number 008 Reported Pain Level: 30, 50, 65, 90 Pain Reading PROBLEM STATEMENT Numerical Pain Rating 15s Numerical Pain Rating Manual Data Entry & Analysis 15 Min. Seated Rest Screening and Questionnaires IMPROVEMENTS •ELECTRONIC OUTPUT using LabVIEW 7.1 Automated Timer Digital Data Storage Digital Display Ability to Export data for further statistical analysis Graphical Output Automated Start of Data Acquisition (contact switch) Audiovisual Cues •Adjustability Hand Dominance Forearm Length Subject Height Adjustable Weight Applied directly over Contact Point •Pain Reading Linear Potentiometers eliminate numerical bias Insert Cannula 30 Min. Adaptation 5 Min. Resting BP Assessment Assess Emotions (EAS) 5 Min. Seated Rest Plasma Sample Assess Barorecptor Sensitivity (BRS) Drug Infusion Over 10 Min. 20 Min. Seated Rest Assess EAS and Side Effects Plasma Sample 5 Min. Rest Assess BRS: 5 Min. Seated Rest Insert Finger Adjust & Apply Pressure LabVIEW collects data for 1 minute, data is saved and exported for future statistical analysis