Blast-Induced Neurotrauma: Surrogate Use, Loading Mechanisms, and Cellular Responses

Category: Publication

Authors: Geoffrey T Desmoulin, Jean-Philippe Dionne

Publication: Journal of Trauma and Acute Care Surgery, Volume 67, Issue 5, Pages 1113-1122

Background: With the onset of improved protective equipment against fragmentation, blast-induced neurotrauma has emerged as the “signature wound” of the current conflicts in the Middle East. Current research has focused on this phenomenon; however, the exact mechanism of injury and ways to mitigate the ensuing pathophysiology remain largely unknown. The data presented and literature reviewed formed the fundamentals of a successful grant from the U.S. Office of Naval Research to Wayne State University.

Methods: This work is a culmination of specialized blast physics and energy-tissue coupling knowledge, recent pilot data using a 12-m shock tube and an instrumented Hybrid III crash test dummy, modeling results from Conventional Weapons effects software, and an exhaustive Medline and government database literature review.

Results: The work supports our hypothesis of the mechanism of injury (described in detail) but sheds light on current hypotheses and how we investigate them. We expose two areas of novel mitigation development. First, there is a need to determine a physiologic and mechanism-based injury tolerance level through a combination of animal testing and biofidelic surrogate development. Once the injury mechanism is defined experimentally and an accurate physiologic threshold for brain injury is established, innovative technologies to protect personnel at risk can be appropriately assessed. Second, activated pathophysiological pathways are thought to be responsible for secondary neurodegeneration. Advanced pharmacological designs will inhibit the key cell signaling pathways. Simultaneously, evaluation of pharmacological candidates will confirm or deny current hypotheses of primary mechanisms of secondary neurodegeneration.

Conclusions: A physiologic- or biofidelic-based blast-induced tolerance curve may redefine current acceleration-based curves that are only valid to assess tertiary blast injury. Identification of additional pharmaceutical candidates will both confirm or deny current hypotheses on neural pathways of continued injury and help to develop novel prophylactic treatments.

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A Technique for Conditioning and Calibrating Force-Sensing Resistors for Repeatable and Reliable Measurement of Compressive Force

Category: Publication

Authors: Rick S Hall, Geoffrey T Desmoulin, Theodore E Milner

Publication: Journal of Biomechanics, Volume 41, Issue 16, Pages 3492-3495

Miniature sensors that could measure forces applied by the fingers and hand without interfering with manual dexterity or range of motion would have considerable practical value in ergonomics and rehabilitation. In this study, techniques have been developed to use inexpensive pressure-sensing resistors (FSRs) to accurately measure compression force. The FSRs are converted from pressure-sensing to force-sensing devices. The effects of nonlinear response properties and dependence on loading history are compensated by signal conditioning and calibration. A fourth-order polynomial relating the applied force to the current voltage output and a linearly weighted sum of prior outputs corrects for sensor hysteresis and drift. It was found that prolonged (>20 h) shear force loading caused sensor gain to change by approximately 100%. Shear loading also had the effect of eliminating shear force effects on sensor output, albeit only in the direction of shear loading. By applying prolonged shear loading in two orthogonal directions, the sensors were converted into pure compression sensors. Such preloading of the sensor is, therefore, required prior to calibration. The error in compression force after prolonged shear loading and calibration was consistently <5% from 0 to 30 N and <10% from 30 to 40 N. This novel method of calibrating FSRs for measuring compression force provides an inexpensive tool for biomedical and industrial design applications where measurements of finger and hand force are needed.

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Selective Control of Leg Muscle Activation Patterns and Ankle Forces Using a Multi-Chambered Stimulation Cuff Implanted on the Sciatic Nerve

Category: Publication

Authors: G Desmoulin, Joaquín Andrés Hoffer

Publication: IFESS 11th Ann. Conf., Phila

A 20-mm Neurocuff(™) with 8 sets of tripolar electrodes placed inside longitudinal chambers separated by insulating ridges (Hoffer et al., 1998) was implanted on the left sciatic nerve of 3 cats. Epimysial bipolar EMG electrodes were sutured onto 8 calf muscles. During the next 3-12 months, force and EMG recruitment properties produced by Neurocuff stimulation were periodically tested under anaesthesia using a 3D force/torque sensor (Gamma ATI).

We found that: 1) every major muscle supplied by the sciatic nerve can be activated through at least one of eight stimulation channels

2) Individual Neurocuff channels typically recruit functionally synergistic muscle groups

3) Single channels produce substantial forces and force recruitment can be well controlled

4) Forces produced by simultaneous activation of two channels sum linearly and predictably, indicating that the axonal pools activated by nearby channels can overlap only modestly.

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Spinal Mechanisms of Pain Control

Category: Publication

Authors: Geoffrey T Desmoulin, Nasif I Yasin, Darryl W Chen

Publication: The Clinical Journal Of Pain, Volume 23, Issue 7, Pages 576-585

Objectives:

To demonstrate initial results using Khan Kinetic Treatment (KKT) as a chronic neck pain treatment and to present pain control mechanistic theory on which the treatment is based.

Methods:

A self-reported functional assessment, neck pain questionnaire, and pain medication dose were used as outcome measures for 44 matched patients randomly split into 2 groups (‘‘treatment’’ and ‘‘control’’). The treatment group underwent a treatment period consisting of several individual KKT treatments, whereas the control group continued conventional therapy.

Results:

Compared with a control group, the treatment group lowered both their self-recorded neck pain scores (P= 0.012) and pain medication dose (P= 0.048), although current functional assessment questionnaires (range of motion, overall activity, and recreation/work activities) did not detect changes (P = 0.233, 0.311, and 0.472, respectively).

Discussion:

We address the theory of the pain control mechanisms of the device in detail. Although we await randomized placebo controlled trials and additional results from ongoing mechanistic studies, initial results show that KKT is potentially an effective treatment for chronic neck pain and may contribute to the reduction of pain relieving medication.

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Lumbar Mechanics From Ultrasound Imaging

Category: Publication

Authors: Geoffrey Desmoulin, Theodore Milner

Publication: Canadian Acoustics, Volume 35, Issue 2, Pages 61-68
School of Kinesiology-Simon Fraser University

The feasibility of estimating lumbar mechanics in-vivo was evaluated using ultrasound imaging. Images were obtained while subjects were seated, with the pelvis fixed, and pulled on an anchored cable by isometrically contracting trunk muscles at different force levels. Linear regression analysis was used to identify ultrasound measurements which were correlated with trunk force. Results suggest that ultrasound is more suitable for estimating lumbar mechanics during lateral flexion than extension of the trunk. A linear trend was found between changes in thickness of some muscles and trunk force, which could provide an alternative to invasive intramuscular electrodes for measuring the activity of non-superficial muscles. A significant limitation, however, is that the magnitude of the changes were frequently very close to the ultrasound resolution.

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Initial Results Using Khan Kinetic Treatment™ as a Low Back Pain Treatment Option

Category: Publication

Authors: Geoffrey T Desmoulin, Nasif I Yasin, Darryl W Chen

Publication: Journal of Musculoskeletal Pain, Volume 15, Issue 3, Pages 91-102

Objectives: Demonstrate initial results using Khan Kinetic Treatment [KKT™] as a low back pain [LBP] treatment option.

Methods: A self-reported functional assessment, LBP questionnaire, and pain medication dose were used as the outcome measures for 48 matched subjects randomly split into two groups [treatment and control]. The treatment group underwent a treatment period consisting of several individual KKT™ treatments over a few weeks period, while the control group continued conventional treatment. A paired t-test analyzed the functional assessment scores and a two group by two LBP score [positive or non-positive] McNemar’s test was used for the LBP questionnaires. Pain medication dose analysis consisted of a two group by two pain medication dose outcome [same or reduced] McNemar’s test.

Results: Compared to a control group, the treatment group lowered both their self-recorded LBP scores [P < 0.001] and showed a strong positive trend to lower their pain medication dose [P = 0.054]. Only the range of motion assessment questionnaire [range of motion, overall activity, and recreation/work activities] detected changes in these measurements [P = 0.046, P = 0.061, P = 0.052, respectively].

Conclusions: Although we await blinded and randomized placebo controlled trials, initial results suggest thatKKT™may be an effective treatment for LBP, may increase the range of motion, and may decrease the need for pain relieving medication.

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