A System to Track Stent Location in the Human Body by Fusing Magnetometer and Accelerometer Measurements.

This paper will introduce a simple locating system to track a stent when it is deployed into a human artery. The stent is proposed to achieve hemostasis for bleeding soldiers on the battlefield, where common surgical imaging equipment such as fluoroscopy systems are not available. In the application of interest, the stent must be guided to the right location to avoid serious complications. The most important features are its relative accuracy and the ease by which it may be quickly set up and used in a trauma situation. The locating approach in this paper utilizes a magnet outside the human body as the reference and a magnetometer that will be deployed inside the artery with the stent. The sensor can detect its location in a coordinate system centered with the reference magnet. In practice, the main challenge is that the locating accuracy will be deteriorated by external magnetic interference, rotation of the sensor, and random noise. These causes of error are addressed in the paper to improve the locating accuracy and repeatability under various conditions. Finally, the system's locating performance will be validated in benchtop experiments, where the effects of the disturbance-eliminating procedures will be addressed.

Functional range of motion of the cervical spine in cervical fusion patients during activities of daily living.

Following cervical spine fusion there is a reduction in maximum range of motion (ROM) but how this impacts activity of daily living (ADLs) and quality of life is unknown. This study's purpose is to quantify maximum and functional cervical spine ROM in patients with multi-level cervical fusion (>3 levels) compared to controls during ADLs and to correlate functional range of motion with scores from patient reported outcomes measures (PROs) including the Comparative Pain Scale (CPS), Fear Avoidance Belief Questionnaire (FABQ), and Neck Disability Index (NDI). An inertial measurement unit (IMU) system quantified ROM during ADLs in the extension/flexion, lateral bending, and axial rotation directions of motion. The reliability of this system was compared to standard optical motion tracking. Fourteen participants (8 females, age = 60.0 years (18.7) (median, (interquartile range)) with a history of multi-level cervical fusion (years post-op 0.9 (0.7)) were compared to 16 controls (13 females, age = 52.1 years (15.8)). PROs were collected for each participant. Fusion participants had significantly decreased maximum ROM in all directions of motion. Fusion participants had decreased ROM for some ADLs (backing up a car, using a phone, donning socks, negotiating stairs). CPS, FABQ, and NDI scores were significantly increased in fusion participants. Reductions in two activities (backing up a car, stair negotiation) correlated with a combination of increased PRO scores. Cervical fusion decreases maximum ROM and is correlated with increased PROs in some ADLs, however there is minimal impact on functional ROM. Investigation into velocity and acceleration may yield categorization of pathologic movement.

A three-tier Rescue stent improves outcomes over balloon occlusion in a porcine model of noncompressible hemorrhage.

BACKGROUND: Noncompressible hemorrhage remains a high-mortality injury, and aortic balloon occlusion poses limitations in terms of distal ischemic injury. Our hypothesis was that a retrievable Rescue stent would confer improved outcome over aortic balloon occlusion. METHODS: A three-tier, retrievable stent graft was laser welded from nitinol and polytetrafluoroethylene to provide rapid thoracic and abdominal coverage with an interval bare metal segment to preserve visceral flow. Anesthetized swine had injury of the thoracic or abdominal aorta followed by balloon occlusion or a Rescue stent. A 1-hour long damage-control phase with blood repletion was used to simulate the prolonged interval between injury and repair, especially in the battlefield setting. Following the damage-control phase, the balloon or stent were retrieved followed by vascular repair and recovery to 48 hours. Animals were compared in terms of hemodynamics, blood loss, neurophysiologic spinal cord ischemia, ischemic organ injury, and survival. RESULTS: Despite antegrade hemorrhage control, balloon occlusion averaged 3.5 L of retrograde hemorrhage, loss of visceral perfusion, and permanent spinal cord ischemia by neurophysiology in six of seven animals. After permanent repair, all balloon occlusion animals died with only a single short term (5 hours) survivor. Conversely, Rescue stent animals revealed rapid hemorrhage control (in under 2 minutes) whether the injury was thoracic or abdominal with improved hemodynamics, preserved visceral flow, reduced spinal cord ischemia, negligible histologic organ injury and survival to end of study in all abdominal injured animals (n = 6) and four of six thoracic injured animals, with two deaths related to arrhythmia. CONCLUSION: Compared with aortic balloon occlusion, a Rescue stent offers superior hemorrhage control and survival by virtue of reduced ischemic injury and direct control of the hemorrhagic injury. The Rescue stent may become a useful tool for damage control, especially on the battlefield where definitive repair presents logistical challenges.

Comprehensive assessment of mechanical behavior of an extremely long stent graft to control hemorrhage in torso.

Traumatic vascular injuries, resulting from either civilian accidents or wounded soldiers, require new endovascular devices (i.e., stent graft) to rapidly control the excessive internal hemorrhage in torso region. Current stent designs are limited by their permanent nature, which is note well suited for emergent placement. A retrievable stent graft could regulate the internal bleeding temporarily, as fast as possible with the most feasible performance, until the patients arrive the hospital to receive the proper treatment. The novel endovascular device of this study is designed according to the anatomy of a porcine model with plans to transition to a human model in the future. The stent graft is manufactured using a substantially long nitinol backbone and covered selectively based on anatomic measurements, with highly stretchable expanded-polytetrafluoroethylene (ePTFE). In this study, our group comprehensively explored designing and manufacturing methods, and their impact on the stent graft performance. Geometric parameters and heat treatment conditions were investigated to show their effect on the radial force of the metallic backbone. As a retrievable device, the resistance force for retrieval as well as deployment were measured, and analyzed to be manipulated through ePTFE covering configurations. In vitro measurements for bleeding were measured using swine aorta to show the functionality of the stent graft under the simulated pulsatile flow circulation. Finally, the stent graft showed substantial effectiveness for hemorrhage control in vivo, using swine model. The new design and fabrication methods enable rapid hemorrhage control that can be removed at the time of a dedicated surgical repair.

Effect of Stroke on Joint Control during Reach-to-Grasp: A Preliminary Study.

We investigated changes in control of inter-segmental dynamics underlying upper extremity dyscoordination caused by stroke. Individuals with stroke and healthy individuals performed a natural reach-to-grasp movement. Kinetic analysis revealed that both groups rotated the shoulder by muscle torque and used interaction torque to rotate the elbow. However, individuals with stroke used interaction torque less than healthy individuals, actively suppressing a substantial portion of it. This resulted in inefficient use of active control and dyscoordination of the upper extremity. The degree of interaction torque suppression and inefficiency of active control at the elbow positively correlated with stroke severity. The increased interaction torque suppression can be a strategy used by individuals with stroke to compensate for deficient feedforward control of this torque.

A Smart Sensing Cannula for Fat Grafting.

Gluteal fat grafting has been highlighted as a significant safety issue in plastic surgery, with a mortality rate as high as one in 3000 cases. Injury to the gluteal veins resulting in fat emboli has been identified as the cause of these mortalities. The gluteal veins lie deep to the gluteal musculature in the buttocks, and it has been suggested that avoiding intramuscular injection of fat may prevent these complications. The authors present a novel injection cannula design that uses impedance sensing to determine the location of the cannula tip. Specifically, the system can determine when the tip of the cannula leaves the subcutaneous plane and enters muscle. The use of this system may prevent inadvertent injury to the gluteal veins and subsequent embolic complications. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Therapeutic, V.

A novel customizable stent graft that contains a stretchable ePTFE with a laser-welded nitinol stent.

Customizable medical devices have recently attracted attentions both in dental and orthopedic device fields, which can tailor to the patients' anatomy to reduce the length of surgery time and to improve the clinical outcomes. However, development of the patient specific endovascular device still remains challenging due to the limitations in current 3D printing technology, specifically for the stent grafts. Therefore, our group has investigated the feasibility of a highly stretchable expanded-polytetrafluoroethylene (ePTFE) tube as a customizable graft material with the laser-welded nitinol backbone. In this study, a highly stretchable ePTFE tube was evaluated in terms of mechanical behaviors, in vitro biocompatibility of ePTFE with various stretchiness levels, and capability for the integration with the laser-welded customizable nitinol stent backbone. A prototype stent graft for the swine's venous size was successfully constructed and tested in the porcine model. This study demonstrates the ability of ePTFE tube to customize the stent graft without any significant issue, for example, sweating through the stretched pores in the ePTFE tube, as well as in vivo feasibility of the device for bleeding control. This novel customizable stent graft would offer possibilities for a wide range of both current and next-generation endovascular applications for the treatment in vascular injuries or diseases. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 911-923, 2019.

Noise in the neonatal intensive care unit: a new approach to examining acoustic events.

INTRODUCTION: Environmental noise is associated with negative developmental outcomes for infants treated in the neonatal intensive care unit (NICU). The existing noise level recommendations are outdated, with current studies showing that these standards are universally unattainable in the modern NICU environment. STUDY AIM: This study sought to identify the types, rate, and levels of acoustic events that occur in the NICU and their potential effects on infant physiologic state. MATERIALS AND METHODS: Dosimeters were used to record the acoustic environment in open and private room settings of a large hospital NICU. Heart and respiratory rate data of three infants located near the dosimeters were obtained. Infant physiologic data measured at time points when there was a marked increase in sound levels were compared to data measured at time points when the acoustic levels were steady. RESULTS: All recorded sound levels exceeded the recommended noise level of 45 decibels, A-weighted (dBA). The 4-h Leq of the open-pod environment was 58.1 dBA, while the private room was 54.7 dBA. The average level of acoustic events was 11-14 dB higher than the background noise. The occurrence of transient events was 600% greater in the open room when compared to the private room. While correlations between acoustic events and infant physiologic state could not be established due to the extreme variability of infant state, a few trends were visible. Increasing the number of data points to overcome the extreme physiologic variability of medically fragile neonates would not be feasible or cost-effective in this environment. CONCLUSION: NICU noise level recommendations need to be modified with an emphasis placed on reducing acoustic events that disrupt infant state. The goal of all future standards should be to optimize infant neurodevelopmental outcomes.

A Nonlinear Dynamics-Based Estimator for Functional Electrical Stimulation: Preliminary Results From Lower-Leg Extension Experiments.

Miniature inertial measurement units (IMUs) are wearable sensors that measure limb segment or joint angles during dynamic movements. However, IMUs are generally prone to drift, external magnetic interference, and measurement noise. This paper presents a new class of nonlinear state estimation technique called state-dependent coefficient (SDC) estimation to accurately predict joint angles from IMU measurements. The SDC estimation method uses limb dynamics, instead of limb kinematics, to estimate the limb state. Importantly, the nonlinear limb dynamic model is formulated into state-dependent matrices that facilitate the estimator design without performing a Jacobian linearization. The estimation method is experimentally demonstrated to predict knee joint angle measurements during functional electrical stimulation of the quadriceps muscle. The nonlinear knee musculoskeletal model was identified through a series of experiments. The SDC estimator was then compared with an extended kalman filter (EKF), which uses a Jacobian linearization and a rotation matrix method, which uses a kinematic model instead of the dynamic model. Each estimator's performance was evaluated against the true value of the joint angle, which was measured through a rotary encoder. The experimental results showed that the SDC estimator, the rotation matrix method, and EKF had root mean square errors of 2.70°, 2.86°, and 4.42°, respectively. Our preliminary experimental results show the new estimator's advantage over the EKF method but a slight advantage over the rotation matrix method. However, the information from the dynamic model allows the SDC method to use only one IMU to measure the knee angle compared with the rotation matrix method that uses two IMUs to estimate the angle.

Exchange rates for intermittent and fluctuating occupational noise: a systematic review of studies of human permanent threshold shift.

OBJECTIVE: The aim of this study was to review the literature regarding human noise-induced permanent threshold shift and to determine whether the observed data agreed with the predictions of two different exchange rates (ERs). DESIGN: An initial list of possibly relevant studies included those cited by authors who endorsed the 3 dB ER, as well as studies in personal files, studies retrieved by a MEDLINE search, and the reference lists of all of these. Criteria for relevance were designed to ensure that exposures were sufficiently intermittent or fluctuating that effective exposure levels based on the 3 dB (LAeq8h) and 5 dB (time-weighted average [TWA]) ERs would differ by at least 1 dB, that at least one of these metrics could be estimated, and that audiometric data were available for groups of defined age, sex, and exposure. Relevant studies were reviewed in detail, and their audiometric data were compared with the predictions of the ISO-1999/ANSI S3.44 model. RESULTS: Nine relevant studies were identified. For six articles, the reported hearing levels were substantially less than would have been predicted from LAeq8h. In each of these cases, TWA would have predicted lower hearing levels than LAeq8h and would have better fit the observed data. In three cases it was not possible to say which ER would have better fit the observed data. CONCLUSIONS: The 3 dB ER systematically overestimates the risk of noise-induced hearing loss for intermittent or fluctuating noise. The 5 dB ER appears to be more accurate, but also overestimates risk, particularly for exposures above 100 dBA.

Chemical and Electrochemical Manipulation of Mechanical Properties in Stimuli-Responsive Copper-Cross-Linked Hydrogels.

Inspiration for the design of new synthetic polymers can be found in the natural world, where materials often exhibit complex properties that change depending on external stimuli. A new synthetic electroplastic elastomer hydrogel (EPEH) that undergoes changes in mechanical properties in response to both chemical and electrochemical stimuli has been prepared based on these precedents. In addition to having the capability to switch between hard and soft states, the presence of both permanent covalent and dynamic copper-based cross links also allows this stimuli-responsive material to exhibit a striking shape memory capability. The density of temporary cross links and the mechanical properties are controlled by reversible switching between the +1 and +2 oxidation states.

Manipulating Mechanical Properties with Electricity: Electroplastic Elastomer Hydrogels.

The dawn of the 21st century has brought with it an increasing interest in emulating the adaptive finesse of natural systems by designing materials with on-demand, tunable properties. The creation of such responsive systems could be expected, based on historical precedent, to lead to completely new engineering design paradigms. Using a bioinspired approach of coupling multiple equilibria that operate on different length scales, a material whose bulk mechanical properties can be manipulated by electrical input has been developed. The new macroscale electroplastic elastomer hydrogels can be reversibly cycled through soft and hard states while maintaining a three-dimensional shape by sequential application of oxidative and reductive potentials. This input changes the cross-linking capacity of iron ions within the gel matrix, between a poorly coordinating +2 and a more strongly binding +3 oxidation state. Inclusion of carbon nanotubes in the hydrogel preparation increases conductivity and decreases transition time.

Protection against noise-induced hearing loss in young CBA/J mice by low-dose kanamycin.

Animal studies indicate that a combination of kanamycin (KM) and noise produces a synergistic effect, whereby the threshold shift from the combination is greater than the sum of the shifts caused by either agent alone. Most such studies have focused on adult animals, and it has remained unclear whether younger, presumably more susceptible, animals show an even greater synergistic effect. The present study tested the hypothesis that young CBA/J mice receiving a low dose of KM (300 mg/kg, 2x/day, s.c.) from 20 to 30 days post-gestational age followed by brief noise exposure (110 dB SPL; 4-45 kHz, 30 s) would show greater noise-induced permanent threshold shifts (NIPTS) than mice receiving either treatment alone. Noise exposure produced 30-40 dB of NIPTS and moderate hair cell loss in young saline-treated mice. KM alone at this dose had no effect on thresholds. Surprisingly, mice receiving KM plus noise were protected from NIPTS, showing ABR thresholds not significantly different from unexposed controls. Mice receiving KM prior to noise exposure also showed significantly less outer hair cell loss than saline-treated mice. Additional experiments indicated protection by KM when the noise was applied either 24 or 48 h after the last KM injection. Our results demonstrate a powerful protective effect of sub-chronic low-dose kanamycin against NIPTS in young CBA/J mice. Repeated kanamycin exposure may establish a preconditioned protective state, the molecular bases of which remain to be determined.

Hearing levels of firefighters: risk of occupational noise-induced hearing loss assessed by cross-sectional and longitudinal data.

OBJECTIVE: It is well known that firefighters face serious risk to their health and safety in the performance of their duties. To determine whether individuals who work as firefighters sustain occupational noise-induced hearing losses, we evaluated results of hearing tests completed by firefighters and compared them with age-matched, non-occupationally exposed groups of individuals. DESIGN: The results of annual audiometric testing and a related questionnaire collected as part of a company-wide hearing conservation program were obtained from two large urban fire departments. The records from 12,609 tests conducted over an 11-year period were evaluated. Hearing levels obtained from the tests were compared with age-matched control populations from an American national standard, and a longitudinal study comparing the rate of hearing loss to that expected due to presbycusis alone was conducted. RESULTS: Comparisons of the data to the national standard indicated that firefighters do not exhibit excessive loss of hearing compared with age-matched, non-occupationally exposed control subjects. The longitudinal study that examined the regression of firefighters' hearing with age compared with the expected presbycasic regression function indicated that the hearing of firefighters in the study declined over the 7-year period at a rate that was less than that expected due to age alone. CONCLUSIONS: The results of this large-scale, cross-sectional, and longitudinal study indicate that firefighters are not at risk for occupational noise-induced hearing loss, even though they work nonstandard shifts and are occasionally exposed to high levels of noise. The results are consistent with the findings but not the conclusions of several other studies of firefighters' hearing.

A multi-station culture force monitor system to study cellular contractility.

Cellular contraction contributes to the formation of scar tissue, which is characterized by an over-produced, disorganized collagen matrix. To study the contractility of cells in vitro and its potential contribution to scar tissue formation, we have developed a multi-station culture force monitor (CFM) system. This system consists of four vertical cantilever beams with semiconductor strain gages and a computerized data acquisition unit to monitor contractile forces of the cells in a collagen gel. Calibration showed that this system has a highly linear voltage-force relationship (R(2) > 0.99). Further, to demonstrate the applicability of this system, contractile forces of human skin fibroblasts in a collagen gel were measured. These fibroblasts were found to produce an average force of 0.2 nN/cell, which is consistent with the data in literature. The significant advantage of this CFM system is its ability to test multiple samples simultaneously. Therefore, the system can facilitate statistical design and analysis of experiments to study the effects of growth factors (e.g., TGF-betas) on cellular contraction and their potential role in scar tissue formation.