Advantages of voice reproduction and the development of a biomimetic self-regulating double-clack valve for a prosthesis of the larynx--a feasibility study.

The human larynx is a versatile organ. Main functions are phonation, protection and regulation of the air ways. Patients suffer severely from the diagnosis of a laryngeal carcinoma of the stages T3 and T4. In most cases this diagnosis will lead to a total laryngectomy, which is usually dissatisfying in the sense of postoperative rehabilitation. The postoperative consequences include the loss of the native voice, the loss of regular air ways via mouth and nose, sense of smell, and the inability to build up an abdominal pressure. In this paper we focus on the feasibility of a modular larynx prosthesis which enables the laryngectomee to talk with his native voice, to breathe via the regular air ways, and to build up abdominal pressure. In particular we will give insights for a postoperative solution - a modular prosthesis based on a biomimetic self-regulating double clack-valve and on a voice reconstruction module, a so called vocoder. The vocoder is a device to reproduce the natural human voice. Most important for the use is an additional device required to analyze, conserve and manage voice characteristics of the patient before surgery. The self-regulating double clack-valve is designed to build up an abdominal pressure e.g. to cough. Therefore, our valve-system is working in both directions - a two-way valve system. By bridging the gap of the regular air ways lost by laryngectomy, the sense of smell and taste are restored. In the following we will present details and characteristics of these two main components required for a modular prosthesis of the larynx in laryngectomees.

Intraoperative pelvic nerve stimulation performed under continuous electromyography of the internal anal sphincter.

PURPOSE: The aim of this animal study was to investigate the effect of intraoperative pelvic nerve stimulation on internal anal sphincter electromyographic signals in order to evaluate its possible use for neuromonitoring during nerve-sparing pelvic surgery. METHODS: Eight pigs underwent low anterior rectal resection. The intersphincteric space was exposed, and the internal (IAS) and external anal sphincter (EAS) were identified. Electromyography of both sphincters was performed with bipolar needle electrodes. Intermittent bipolar electric stimulation of the inferior hypogastric plexus and the pelvic splanchnic nerves was carried out bilaterally. The recorded signals were analyzed in its frequency spectrum. RESULTS: In all animals, electromyographic recordings of IAS and EAS were successful. Intraoperative nerve stimulation resulted in a sudden amplitude increase in the time-based electromyographic signals of IAS (1.0 (0.5-9.0) µV vs. 4.0 (1.0-113.0) µV) and EAS (p < 0.001). The frequency spectrum of IAS in the resting state ranged from 0.15 to 5 Hz with highest activity in median at 0.77 Hz (46 cycles/min). Pelvic nerve stimulation resulted in an extended spectrum ranging from 0.15 to 20 Hz. EAS signals showed higher frequencies mainly in a range of 50 to 350 Hz. However, after muscle relaxation with pancuronium bromide, only the low frequency spectrum of the IAS signals was still present. CONCLUSIONS: Intraoperative verification of IAS function by stimulation of pelvic autonomic nerves is possible. The IAS electromyographic response could be used to monitor pelvic autonomic nerve preservation.

A flexible microelectrode for mouse EEG.

Electroencephalography (EEG) of the mouse brain offers the advantage to monitor brain states in freely moving conditions under genetic or molecular manipulation. We present a novel, flexible, and biocompatible microfabricated electrode based on polyimide to record a multi-channel EEG from a mouse. Our microelectrode has 32 recording electrodes, including two ground electrodes. The connectors for the signal transmission are carefully affixed to the microelectrode. The overall weight of the microelectrode does not exceed 150 mg, including connectors. The implantation of the microelectrodes does not require invasive surgery and the mouse can be easily discharged from the wires when it is not being recorded. Simultaneous measurements with the microelectrode and a conventional screw electrode show that the microelectrode successfully collects the broad band EEG signals from the skull.

Electrode structures for acquisition and neural stimulation controlling the cardiovascular system.

In this study we present an innovative electrode system, for many different applications in the field of cardiovascular diseases. It is a combination of intelligent communicating dry-surface electrodes, which are able to interact with different sensors especially with an invasive, ultra flexible electrode-system. Dry and smart surface electrodes, which can be integrated in textiles and therefore such electrode are almost "invisible" for patients, are used for ECG acquisition and can be integrated in a communication network. In combination with a pulse oximeter or impedance spectroscopy the pulse transit time (PTT) can be calculated. Additionally, with invasive electrodes the nervous vagus can be stimulated and therefore cardiovascular functions can be controlled. The association of an implanted stimulator with an interacting and smart monitoring system results into a cardiovascular controlling. In this work we will focus on the feasibility, suitability, fabrication and characterization of invasive and dry-surface electrode systems as a basic element and foundation for cardiovascular regulation in a closed loop.

An optically powered single-channel stimulation implant as test system for chronic biocompatibility and biostability of miniaturized retinal vision prostheses.

A microsystem based microimplant with an optically powered single-channel stimulator was designed and developed as test system for an epi-retinal vision implant. Biostability of the hybrid assembly and the encapsulation materials were evaluated in pilot experiments in chronic implantations in a cat animal model. The implant was fabricated on a flexible polyimide substrate with integrated platinum electrode, interconnection lines, and contact pads for hybrid integration of electronic components. The receiver part was realized with four photodiodes connected in series. A parylene C coating was deposited on the electronic components as insulation layer. Silicone rubber was used to encapsulate the electronics in the shape of an artificial intraocular lens to allow proper implantation in the eye. Pilot experiments showed the biostability of the encapsulation approach and full electric functionality of the microimplant to generate stimulation currents over the implantation period of three months in two cats. In one cat, electrical stimulation of the retina evoked neuronal responses in the visual cortex and indicated the feasibility of the system approach for chronic use.

Design, in vitro and in vivo assessment of a multi-channel sieve electrode with integrated multiplexer.

This paper reports on the design, in vitro and in vivo investigation of a flexible, lightweight, polyimide based implantable sieve electrode with a hybrid assembly of multiplexers and polymer encapsulation. The integration of multiplexers enables us to connect a large number of electrodes on the sieve using few input connections. The implant assembly of the sieve electrode with the electronic circuitry was verified by impedance measurement. The 27 platinum electrodes of the sieve were coated with platinum black to reduce the electrode impedance. The impedance magnitude of the electrode sites on the sieve (geometric surface area 2,200 microm(2)) was |Z(f=1kHz)| = 5.7 kOmega. The sieve electrodes, encased in silicone, have been implanted in the transected sciatic nerve of rats. Initial experiments showed that axons regenerated through the holes of the sieve and reinnervated distal target organs. Nerve signals were recorded in preliminary tests after 3-7 months post-implantation.