A fully integrated physical activity sensing circuit for implantable pacemakers

PostprintThis paper shows the implementation of a fully integrated Gm-C 0.5-7Hz bandpass filter-amplifier with gain G=400, for a piezoelectric accelerometer which is part of a rate adaptive pacemaker. The fabricated circuit operates up to 2V power supply, consumes only 230nA current, and achives 2.1μVrms input noise. Detailed circuit specifications, measurements, and a comparative analysis of the system performance are presented

Future of smart cardiovascular implants

Cardiovascular disease remains the leading cause of death in Western society. Recent technological advances have opened the opportunity of developing new and innovative smart stent devices that have advanced electrical properties that can improve diagnosis and even treatment of previously intractable conditions, such as central line access failure, atherosclerosis and reporting on vascular grafts for renal dialysis. Here we review the latest advances in the field of cardiovascular medical implants, providing a broad overview of the application of their use in the context of cardiovascular disease rather than an in-depth analysis of the current state of the art. We cover their powering, communication and the challenges faced in their fabrication. We focus specifically on those devices required to maintain vascular access such as ones used to treat arterial disease, a major source of heart attacks and strokes. We look forward to advances in these technologies in the future and their implementation to improve the human condition

Multi-Electrode Pacemaker

O principal objetivo desta dissertação é apresentar uma pesquisa de mercado sobre as tecnologias existentes bem como descrever um método abrangente para alcançar o protótipo de um pacemaker implantável com recursos sem fio.The main objective of this dissertation is to present a market survey on existing technologies as well as to depict a comprehensive method to achieve the prototype of an implantable pacemaker with wireless capabilities

Advanced intelligent control and optimization for cardiac pacemaker systems

Since cardiovascular diseases are major causes of morbidity and mortality in the developed countries and the number one cause of death in the United States, their accurate diagnosis and effective treatment via advanced cardiac pacemaker systems have become very important. Intelligent control and optimization of the pacemakers are significant research subjects. Serious but infrequently occurring arrhythmias are difficult to diagnose. The use of electrocardiogram (ECG) waveform only cannot exactly distinguish between deadly abnormalities and temporary arrhythmias. Thus, this work develops a new method based on frequency entrainment to analyze pole-zero characteristics of the phase error between abnormal ECG and entrained Yanagihara, Noma, and Irisawa (YNI)-response. The thresholds of poles and zeros to diagnose deadly bradycardia and tachycardia are derived, respectively, for the first time. For bradycardia under different states, a fuzzy proportional-integral-derivative (FPID) controller for dual- sensor cardiac pacemaker systems is designed. It can automatically control the heart rate to accurately track a desired preset profile. Through comparing with the conventional algorithm, FPID provides a more suitable control strategy for offering better adaptation of the heart rate, in order to fulfill the patient\u27s physiological needs. This novel control method improves the robustness and performance of a pacemaker system significantly. Higher delivered energy for stimulation may cause higher energy consumption in pacemakers and accelerated battery depletion. Hence, this work designs an optimal single-pulse stimulus to treat sudden cardiac arrest, while minimizing the pulse amplitude and releasing stimulus pain. Moreover, it derives the minimum pulse amplitude for successful entrainment. The simulation results confirm that the optimal single-pulse is effective to induce rapid response of sudden cardiac arrest for heartbeat recovery, while a significant reduction in the delivered energy is achieved. The study will be helpful for not only better diagnosis and treatment of cardiovascular diseases but also improving the performance of pacemaker systems

A 110 nA pacemaker sensing channel in CMOS on silicon-on-insulator

PostprintThe design of a sensing channel for implantable cardiac pacemakers in CMOS on silicon-on-insulator (SOI) technology is presented. The total current consumption is lowered to only 110nA thanks to the optimization at the architectural level, the application of a new class AB design approach at the operational transconductance amplifier (OTA) and the exploitation of the improved characteristics of thin-film fully depleted SOI CMOS technology. The core of the prototyped sense channel (OTA and comparator) occupies 0.06mm/sup 2/ in a 3/spl mu/m technology and is suitable for operation from implantable grade batteries with power supply voltages from 2.8V down to 2V. Experimental results of the building blocks and complete sensing channel performance are presented. The achieved results demonstrate the benefits of fully depleted SOI CMOS technology for micropower applications

Beyond Tissue replacement: The Emerging role of smart implants in healthcare

Smart implants are increasingly used to treat various diseases, track patient status, and restore tissue and organ function. These devices support internal organs, actively stimulate nerves, and monitor essential functions. With continuous monitoring or stimulation, patient observation quality and subsequent treatment can be improved. Additionally, using biodegradable and entirely excreted implant materials eliminates the need for surgical removal, providing a patient-friendly solution. In this review, we classify smart implants and discuss the latest prototypes, materials, and technologies employed in their creation. Our focus lies in exploring medical devices beyond replacing an organ or tissue and incorporating new functionality through sensors and electronic circuits. We also examine the advantages, opportunities, and challenges of creating implantable devices that preserve all critical functions. By presenting an in-depth overview of the current state-of-the-art smart implants, we shed light on persistent issues and limitations while discussing potential avenues for future advancements in materials used for these devices

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

Wireless Patient Monitoring over 4G Network

The purpose of this thesis is to explain how remote patient monitoring systems work over the 4G network using wearable sensors and corresponding interface devices. Gathered data from the sensing devices are carried over the Monitoring Wireless Sensor Network to the more elaborate 4G Network where the data is then relayed to the interface devices for reading, storage, interpretation and effective utilization. This thesis describes the underlying technologies and principles of sensors and sensor net-works, the concept of the 4G Network and how it integrates with the sensor network. The goal of Wireless Patient Monitoring over the 4G Network is link the spatial gap that exist between Healthcare and ICT, this will in turn enhance patients care efficiency while cutting costs, maximising profits and increase security while monitoring patients. This thesis is important in that it gives the reader an overview and basic idea of how a wireless patient monitoring system works over the 4G Network. An increasing number of ICT firms, healthcare and medical institutions are investing heavily on remote patient monitoring systems technologies and this thesis provides the reader the insight of how such systems work and how they can be implemented

Very large time constant Gm-C Filters

In this study a set of tools for the design of fully integrated transconductor-capacitor (Gm-C) filters, with very large time constants and current consumption under one micro-Ampere are presented. The selected application is a 2nd order bandpass-filter-amplifier, with a gain of 400 from 0.5 to 7Hz, carrying out the signal conditioning of a piezoelectric accelerometer which is part of an implantable cardiac pacemaker. The main challenge is to achieve very large time constants, without using any discrete external component. The chosen circuit technique to fulfill the requirement is series-parallel current division applied to standard symmetrical transconductors (OTAs). These circuits have demonstrated to be an excellent solution regarding their occupied area, power consumption, noise, linearity, and particularly offset. OTAs as low as 33pS -equivalent to a 30G resistor-, with up to 1V linear range, and input referred offset of a few mV, were designed, fabricated in a standard 0.8 micron CMOS technology, and tested. The application requires the series-parallel association of a large number of transistors, and the use of bias currents as low as a few pico-Amperes, which is not very common in analog integrated circuits. In this case the designer should employ maximum care in the selection of the transistor models to be used. A central aspect of this thesis was also to evaluate and develop noise and offset estimation models which was not obvious in the very beginning of the research. In the first two chapters an introduction to the target application is presented, and several MOS transistor characteristics in terms of the inversion coefficient -using the ACM transistor model- are evaluated. In chapter 3 it is discussed whether the usual flicker and thermal noise models are consistent regarding series-parallel association, and adequately represent the expected noise behavior under different bias conditions. A consistent, physics-based, one-equation-all-regions model for flicker noise in the MOS transistor is then presented. Several noise measurements are included demonstrating that the new model accurately fits widely different bias situations. A new model for mismatch offset in MOS transistors is presented, as a corollary of the flicker noise analysis. Finally, the correlation between flicker noise and mismatch offset, that can be seen as a DC noise, is shown. In chapter 4, the design of OTAs with an extended linear range, and very low transconductance, using series-parallel current division is presented. Precise tools are introduced for the estimation of noise and mismatch offset in series-parallel current mirrors, that are shown to help in the reduction of inaccuracies in the copy of currents with a large copy factor. The design and measurement of several OTA examples are presented. In chapter 5, the developed tools, and the OTAs shown, are employed in the design of the above mentioned filter for the piezoelectric accelerometer. A general methodology for the design of Gm-C filters with similar characteristics is established. The filter was fabricated and tested, successfully operating with a total power consumption of 233nA, up to a 2V power supply, with an input noise and mismatch offset of 2-4 Vrms, and 18 V respectively. To summarize the main results obtained were: The development of a new flicker noise model, the study of the effect of mismatch regarding series-parallel association, a new design methodology for OTAs and Gm-C filters. It is our hope that this constitutes a helpful set of tools for the circuit designer.En esta tesis se presenta un conjunto de herramientas para el diseño de circuitos integrados que implementan filtros transconductor-capacitor (Gm-C), de muy altas constantes de tiempo, con bajo ruido, y consumo de corriente por debajo del micro-Ampere. Como ejemplo de aplicación se toma un amplificador-pasabanda 2º orden, de ganancia 400 en la banda de 0.5 a 7Hz, que realiza el acondicionamiento de señal de un acelerómetro piezoeléctrico a ser empleado en un marcapasos implantable. El principal desafío es realizar en dicho filtro de tiempo continuo, muy altas constantes de tiempo sin usar componentes externos. La técnica elegida para alcanzar tal objetivo es la división serie-paralelo de corriente en transconductores (OTAs) simétricos estándar. Estos circuitos demostraron ser una excelente solución en cuanto al área ocupada, su consumo, ruido, linealidad, y en particular offset. Se diseñaron, fabricaron, y midieron, OTAs hasta 33pS -equivalente a una resistencia de 30G -, con hasta 1V de rango de lineal, y offset a la entrada de algunos mV, utilizando una tecnología CMOS de 0.8 micras de largo mínimo de canal. La aplicación requiere la asociación serie-paralelo de un gran número de transistores, y polarización con corrientes de hasta pico-Amperes, lo que constituye una situación poco frecuente en circuitos integrados analógicos. En este marco el diseñador debe elegir los modelos de transistor con sumo cuidado. Un aspecto central de esta tesis es también, el estudio y presentación de modelos adecuados de ruido y offset, que no resultan obvios al principio. En los primeros dos capítulos se realiza una introducción y se revisa, utilizando el modelo ACM, diferentes características del transistor MOS en función del nivel de inversión. En el capítulo 3 revisa la pertinencia y consistencia frente a la asociación serie-paralelo, de los modelos usuales de ruido de flicker o 1/f, y térmico. Luego se presenta, incluyendo medidas, un nuevo modelo físico, consistente, simple, y válido en todas las regiones de operación del transistor MOS, para el ruido de flicker. Como corolario a este estudio se presenta un nuevo modelo para estimar el desapareo entre transistores, en función no solo de la geometría, pero también de la polarización. Se demuestra la correlación, debido a su origen físico análogo, entre el ruido de flicker y el offset por desapareo que puede ser visto como un ruido en DC. En el capítulo 4 se presenta el diseño de OTAs con rango de linealidad extendido, y muy baja transconductancia, utilizando división serie-paralelo de corriente. Se presentan herramientas precisas para la estimación de offset y ruido y se demuestra la utilidad de la técnica para reducir el offset en espejos de corriente. Se presenta el diseño y medida de diversos OTAs. En el capítulo 5, las herramientas desarrolladas, y los OTAs presentados, son empleados en el diseño del filtro descripto para un acelerómetro piezoeléctrico. Se establece una metodología general para el diseño de filtros Gm-C con características similares. El filtro se fabricó y midió, operando en forma satisfactoria, con un consumo total de 230nA y hasta los 2V de tensión de alimentación, con ruido y offset a la entrada de tan solo 2-4 Vrms, y 18 V respectivamente. El desarrollo de un nuevo modelo de ruido 1/f para el transistor MOS, el estudio de la influencia del offset frente a la asociación serie-paralelo y su aplicación en OTAs, la metodología de diseño empleada, la demostración del uso de técnicas novedosas en una aplicación como la elegida que tiene relevancia tecnológica e interés académico; esperamos que todo ello constituya una contribución valiosa para la comunidad científica en microelectrónica y un conjunto de herramientas de utilidad para el diseño de circuitos