Gurpreet S. Dhillon

Direct neural sensory feedback and control of a prosthetic arm

Evidence indicates that user acceptance of modern artificial limbs by amputees would be significantly enhanced by a system that provides appropriate, graded, distally referred sensations of touch and joint movement, and that the functionality of limb prostheses would be improved by a more natural control mechanism. We have recently demonstrated that it is possible to implant electrodes within individual fascicles of peripheral nerve stumps in amputees, that stimulation through these electrodes can produce graded, discrete sensations of touch or movement referred to the amputees phantom hand, and that recordings of motor neuron activity associated with attempted movements of the phantom limb through these electrodes can be used as graded control signals. We report here that this approach allows amputees to both judge and set grip force and joint position in an artificial arm, in the absence of visual input, thus providing a substrate for better integration of the artificial limb into the amputees body image. We believe this to be the first demonstration of direct neural feedback from and direct neural control of an artificial arm in amputees.

Neuroprosthetics theory and practice

Neuroanatomy and neurophysiology extracellular stimulation and recording - theory and models immunology materials for nerve stimulation and recording peripheral nerve and muscle - stimulation and recording electrodes and techniques CNS stimulation and recording electrodes and techniques existing FES systems and signal processing future FES systems/devices/brain-computer interfaces experimentation and device approval.

Acute peripheral nerve recording Characteristics of polymer-based longitudinal intrafascicular electrodes

We examined the recording characteristics of two different types of polymer-based longitudinal intrafascicular electrodes (LIFEs) in peripheral nerve: single-stranded (s-polyLIFEs) and multistranded (m-polyLIFEs). Recordings were also made from Pt-Ir wire-based electrodes (PtIrLIFEs) as a control. The electrodes were implanted in either tibial or medial gastrocnemius branches of the rabbit sciatic nerve, and in the sciatic nerve of rats. Recorded neural activity induced by manually elicited afferent neural activity showed that both polyLIFE versions performed comparably to PtIrLIFEs.

Fabrication and characteristics of an implantable, polymer-based, intrafascicular electrode

We describe new manufacturing techniques and physical properties of an improved polymer-based longitudinal intrafascicular electrode (polyLIFE). Modifications were made to correct: (1) poor metal film adhesion and fatigue resistance, (2) inconsistent insulation adhesion and control over recording/stimulation zone length, and (3) insufficient tensile strength for clinical use. Metal adhesion was significantly improved by both plasma treatment and fiber rotation (about the long axis) during metal deposition. Fatigue resistance was improved by reduction in sputtering energy (time x power) combined with long axis rotation, resulting in thin metal films that were 250 times more resistant to cyclic bending fatigue. Insulation adhesion was enhanced with the application of an adhesion-promoting silicone (MED2-4013, Nusil), while the recording/stimulation zone length was controlled to 1 +/- 0.2mm (mean +/- S.D.). The polyLIFE was made more robust by the inclusion of three individually metallized fibers, improving its tensile strength by a factor of 4 while producing minimal changes to its overall stiffness. However, the metallized fiber redundancy did not significantly affect fatigue resistance. The manufacturing changes described in this study enable the construction of more mechanically robust polyLIFEs, which should provide greater success when chronically implanted in peripheral nerves.

Fetal left‐sided cardiac structural dimensions in left‐sided congenital diaphragmatic hernia – association with severity and impact on postnatal outcomes

Fetuses with congenital diaphragmatic hernia (CDH) demonstrate varying degrees of left heart hypoplasia. Our study assesses the relationship between fetal left‐sided cardiac structural dimensions, lung size, percentage liver herniation, lung‐to‐head ratio, postnatal left‐sided cardiac structural dimensions, and postnatal outcomes.

The impact of fetal endoscopic tracheal occlusion in isolated left‐sided congenital diaphragmatic hernia on left‐sided cardiac dimensions

Fetal endoscopic tracheal occlusion (FETO) is offered to fetuses with congenital diaphragmatic hernia (CDH) and severe lung hypoplasia to promote lung growth and may secondarily affect left heart growth. The effects of FETO on left heart hypoplasia (LHH) are not described post‐CDH repair.

Predictive value of oxygenation index for outcomes in left-sided congenital diaphragmatic hernia

BACKGROUND & OBJECTIVES Congenital Diaphragmatic Hernia (CDH) is associated with significant morbidity and mortality. This study compares the efficacy of the highest oxygenation index in the first 48 h (HiOI) versus current prenatal indices to predict survival and morbidity. METHODS Medical records of 50 prenatally diagnosed, isolated, left-sided CDH patients treated from January 2011 to April 2016 were reviewed. Data abstracted included HiOI, lung to head ratio (LHR), observed to expected total fetal lung volume (O/E TFLV), percent liver herniation (%LH), 6 month survival, respiratory support at discharge, ventilator days and length of stay. Data were analyzed using parametric and nonparametric tests and regression analyses as appropriate. RESULTS HiOI was associated with significantly increased LOS (p<0.001), respiratory support at discharge (p<0.001), greater ventilator days (p=0.001) and higher odds of death (p=0.004) with risk of death increasing by 5% for every one-unit increase in OI. HiOI was statistically a better predictor of LOS than O/E TFLV (p=0.007) and %LH (p=0.02). CONCLUSIONS In isolated, left-sided CDH patients, HiOI is associated with higher mortality, greater length of stay, more ventilator days and increased respiratory support at discharge. HiOI is a better predictor of length of stay than O/E TFLV and %LH. TYPE OF STUDY Retrospective Study LEVEL OF EVIDENCE: II.

Transposition of the great arteries: When echocardiography does not match the clinical picture

Aortopulmonary window (APW) is a rare form of congenital heart disease seen in isolation or with complex cardiac lesions. APW has been associated with other cardiac defects such as interrupted aortic arch and Tetralogy of Fallot, but few cases have been reported of APW associated with transposition of the great arteries (TGA). In a newborn with TGA and intact ventricular septum, diagnosis of APW requires a high index of suspicion. This article reviews the literature on TGA with APW and illustrates the importance of additional evaluation in neonates with TGA when oxygen saturation and PaO2 do not match predicted clinical values.