Assessing Cerebral Hemodynamic Stability After Brain Injury.

Objective: Following brain injury, unstable cerebral hemodynamics can be characterized by abnormal rises in intracranial pressure (ICP). This behavior has been quantified by the RAP index: the correlation (R) between ICP pulse amplitude (A) and mean (P). While RAP could be a valuable indicator of autoregulatory processes, its prognostic ability is not well established and its validity has been questioned due to potential errors in measurement.

Trending autoregulatory indices during treatment for traumatic brain injury.

Our goal is to use automatic data monitoring for reliable prediction of episodes of intracranial hypertension in patients with traumatic brain injury. Here we test the validity of our method on retrospective patient data. We developed the Continuous Hemodynamic Autoregulatory Monitor (CHARM), that siphons and stores signals from existing monitors in the surgical intensive care unit (SICU), efficiently compresses them, and standardizes the search for statistical relationships between any proposed index and adverse events.

Clinical Risk Factors for Orthostatic Hypotension: Results Among Elderly Fallers in Long-Term Care.

Background: Patients at greatest risk for fall-related injuries are older adults with orthostatic hypotension (OH), a condition which drops blood pressure. This study sought to determine salient demographic and patient-level factors increasing risk for OH among a sample of elderly fallers.

Methods: Data analysis for this retrospective study sought to assess the relationship between various demographic and clinical risk factors and the likelihood of OH.

Biomechanical analysis of spasticity treatment in patients with multiple sclerosis.

Objectives: New metrics for clinical spasticity are needed to assess motor performance, since scales such as the Ashworth and Tardieu are unreliable. Here, we assessed outcomes of baclofen treatment in patients with multiple sclerosis (MS) using biomechanical analysis of voluntary movements.

Methods: Patients with MS and symptomatic limb spasticity were recruited for a pre-post baclofen titration study, along with age-matched healthy controls.

Proceedings of the first workshop on Peripheral Machine Interfaces: going beyond traditional surface electromyography.

One of the hottest topics in rehabilitation robotics is that of proper control of prosthetic devices. Despite decades of research, the state of the art is dramatically behind the expectations. To shed light on this issue, in June, 2013 the first international workshop on Present and future of non-invasive peripheral nervous system (PNS)-Machine Interfaces (MI; PMI) was convened, hosted by the International Conference on Rehabilitation Robotics.

Piezoelectric substrates promote neurite growth in rat spinal cord neurons.

We tested the possibility that exogenous electrical activity from a piezoelectric substrate could influence neuronal structure in cultured spinal cord neurons. Oscillating electrical fields were delivered to rat neurons via substrates consisting of poly(vinylidene fluoride) film, both in its piezoelectric (PZ) and non-piezoelectric (PV) forms. To induce oscillating electrical fields at the film surfaces, a 50 Hz mechanical vibration was applied.

Reformulation in the phase plane enhances smoothness rater accuracy in stroke.

To improve the characterization of motor impairment, we compared the sensitivities of a phase plane metric with temporal domain measures derived from integrated squared jerk (ISJ). Five subjects with stroke and a cohort of 21 neurologically intact volunteers performed self-paced, isolated elbow flexions. Analysis of angular trajectories from the stroke group revealed that temporal domain metrics failed to detect a performance deficit at the p < .

Improving fine motor function after brain injury using gesture recognition biofeedback.

Purpose: We developed a gesture recognition biofeedback (GRB) device for improving fine motor function in persons with brain injury using surface muscle pressures of the forearm to provide real-time visual biofeedback. The GRB apparatus is easy to don by moderately impaired users and does not require precise placement of sensors.

Method: The efficacy of GRB training with each subject was assessed by comparing its effectiveness against standard repetitive training without feedback.

Relating biceps EMG to elbow kinematics during self-paced arm flexions.

Repetitive reaching movements to a fixed target can be generally characterized by bell-shaped velocity profiles and sigmoidal trajectories with variable morphologies across multiple repetitions. A neuromuscular correspondence of these kinematic variations has thus far eluded electromyographic (EMG) analysis. We recorded EMG and elbow kinematics from fourteen healthy individuals performing repetitive, self-paced, isolated elbow flexions, with their arms supported against gravity.

Surface muscle pressure as a measure of active and passive behavior of muscles during gait.

While surface electromyography (SEMG) can accurately register electrical activity of muscles during gait, there are no methods to estimate muscular force non-invasively. To better understand the mechanical behavior of muscle, we evaluated surface muscle pressure (SMP) in conjunction with SEMG. Changes in anterior thigh radial pressure during isometric contractions and gait were registered by pressure sensors on the limb.

Training grip control with a Fitts' paradigm: a pilot study in chronic stroke.

Study Design: A clinical measurement study.

Purpose: To test the applicability of Fitts' paradigm to grasping tasks in individuals with chronic stroke.

Introduction: Fitts' Law relates the time of target achievement to task difficulty in repetitive motor tasks.

Spatial resolution of spontaneous accelerations in reaching tasks.

Reaching tasks are considered well-executed if they appear "smooth," a quality that is typically quantified by its opposite, jerk, the rate of change of acceleration. While jerk is a theoretically sound measure, its application to spastic individuals sometimes yields counter-intuitive results, and does not reveal motor impairment across the workspace. To more generally quantify spontaneous accelerative transients (SATs) within a movement, a pseudo-wavelet transform was devised that iteratively compared angular trajectories to a series of straight-line approximants.

Pressure signature of forearm as predictor of grip force.

We studied the relationship between grip force and external forearm pressure in nondisabled subjects using force myography (FMG). FMG uses a sensorized cuff surrounding the forearm to register the distributed mechanical force, detecting pressure on the sensors generated by the volumetric changes of the underlying musculo-tendinous complex. Each of nine nondisabled subjects donned the FMG cuff and applied grip forces to a cylindrical dynamometer; grip forces ranged from 0% to 100% of the subjects' maximum voluntary contraction.

Inter-limb transfer of learned ankle movements.

Inter-limb learning transfer (ILT) between the upper-limbs has been well documented, but no corresponding study of the lower limbs has been done. We investigated ILT in the lower limbs of subjects who learned to move a cursor toward targets within 800 ms using ankle movements: plantar/dorsi-flexion and inversion/eversion. Twenty-two healthy right-dominant subjects were divided into two groups: half performed the tasks first using the right foot (group RL), and the other half performed it first with the left foot (group LR).

Power spectral analysis of heart rate in relation to sleep position.

We used spectral analysis of heart rate variability, as a measure of autonomic tone, to determine spectral power differences in infants sleeping supine and prone. We studied 29 infants with a birth weight of 1,915 +/- 939 g, at the postconceptional age of 36 +/- 2 weeks. We then calculated total power (TP), low-frequency power (LF, 0.

The bionic man: restoring mobility.

Bionics engineers are making increasingly bold and successful use of their tools to restore mobility to persons with missing or nonfunctional limbs. These tools include the latest materials, minielectronics and megacomputers, advanced robotic mechanisms, and algorithms. With crucial help from their pioneering users, they are learning how and where the residual sensorimotor system can be tapped in order to transmit its intents to replacement or reactivated body parts.

Biomimetic finger control by filtering of distributed forelimb pressures.

A linear filter was developed for decoding finger commands from volitional pressures distributed within the residual forelimb. Filter parameters were based on dynamic pressures recorded from the residual limb within its socket, during specific finger commands. A matrix of signal features was derived from eight-dimensional (8-D) pressure vectors, and its pseudoinverse comprised the filter parameters.

Spectral analysis of heart variability in the newborn infant.

We investigated the relationship between spectral power and both mean heart rate (HR) and heart rate variability (HRV). Spectral power was calculated using digital heart rate recordings from term infants. Regression analysis revealed a positive correlation between low-frequency (LF) sympathetic power and HR, and a negative correlation between high-frequency (HF) parasympathetic power and HR.

Spectral analysis of heart rate variability in premature infants with feeding bradycardia.

An elevated level of baseline parasympathetic activity was noted in a group of premature infants suffering from bradycardia during feeding. At approximately 34 wk post-conceptional age, the heart rates of 12 infants with feeding bradycardia (birth weight = 1539 +/- 279 g; gestational age = 31.0 +/- 1.

A biomimetic controller for a multifinger prosthesis.

A novel controller for a multifinger hand prosthesis was developed and tested to measure its accuracy and performance in transducing volitional signals for individual "phantom" fingers. Pneumatic sensors were fabricated from open-cell polymeric foam, and were interposed between the prosthetic socket and superficial extrinsic tendons associated with individual finger flexion. Test subjects were prompted to move individual fingers or combinations thereof to execute either taps or grasps.

Acute effects of thyroid hormone analogs on sodium currents in neonatal rat myocytes.

We previously reported that T3(3,3',5-triiodo-L-thyronine) acutely increases sodium currents (INa) in neonatal rat myocytes. Here we compare the effects of several thyroid hormone analogs, including T4(3,3',5,5'-tetraiodo-L-thyronine), rT3(3,3',5'-triiodo-L-thyronine), D-T3(3,3',5-triiodo-D-thyronine), 3,5-T2(3,5-diiodo-L-thyronine), DIT (3,5-diiodo-L-tyrosine), MIT (3-monoiodo-L-tyrosine), tetrac (3,3',5,5'-tetraiodo-thyroacetic acid), triac (3, 3',5-triiodo-thyroacetic acid), and tyrosine, on INa in cultured neonatal rat myocytes (n ranged from 9 to 28 for each comparison). T4, T3, 3,5-T2, and DIT (10 n m) all increased current density relative to control to a similar degree: to 1.

Rheological behavior of rat mesangial cells during swelling in vitro.

The response of cells to mechanical forces depends on the rheological properties of their membranes and cytoplasm. To characterize those properties, mechanical and electrical responses to swelling were measured in rat mesangial cells (MC) using electrophysiologic and video microscopic techniques. Ion transport rates during hyposmotic exposures were measured with whole-cell recording electrodes.

Recognition of individual heart rate patterns with cepstral vectors.

Heart rate patterns may contain diagnostic as well as forensic information. To test these possibilities, individual heart rate patterns were represented as heart-rate cepstral vectors (HRCVs) computed in 12 dimensions via linear predictive coding (LPC) of brief segments of heart rate. A library of codebook vectors was computed for 12 cardiac patients from a standard ECG database.

Cation conductance regulated by ambient Cl- in cultured rat mesangial cells.

Several functions of mesangial cells, such as contraction and release of nitric oxide, are dependent on the ambient Cl- concentration. Herein we describe a direct effect of Cl- on mesangial cell membrane conductance. Rat mesangial cells were isolated, cultured, and were patch-clamped in the whole-cell configuration.

The role of thermal feedback in electrosurgical tissue heating.

Thermal dependence of tissue resistivity was incorporated into a compartmental tissue model that predicted the interaction between power delivery from electrosurgical units (ESUs) and tissue heating. Simulations showed that as tissue resistance declines with heating, a positive feedback loop from tissue to generator is created that can promote alternate site burning. This study describes how the thermal behaviour of tissue resistance influences the output of microprocessor-controlled thermal generators, especially when used in the monopolar mode.