Implanted medical

AH implantable medical devices ate complex in design, materials, and implementation procedures. The biocompatibiUty, biodurabiUty, and efficacy of medical devices are the subject of extensive research by biomaterials scientists, device manufacturers, and health care professionals. 

Community-wide regulation of medical devices commenced with the introduction of Council Directive 90/385/EEC of 20 June 1990 on the approximation of the laws of the Member States relating to active implantable medical devices. Two further base directives followed that cover all other medical devices The Medical Devices Directive 93/42/EEC and The In Vitro Diagnostics Directive 98/79/EC. All three base directives are similar in content and structure. However, it should be noted that, in addition to dealing with the particular subject matter, the Medical Devices Directive and the In Vitro Diagnostics Directive also contained amendments to the previous device directives. The Medical Devices Directive amended articles in the Active Implantable Medical Devices Directive, while the In Vitro Diagnostics Directive amended articles in the Medical Devices Directive. 

The subcategories, active implantable medical devices and in vitro medicai devices are further defined as ... 

As a general rule, clinical data are required as evidence to support conformity with the requirements of the Active Implantable Medical Devices (AIMD) and the Medical Device (MD) directives with regards to safety and effectiveness under the normal conditions of use, evaluation of undesirable side effects, and the acceptability of the benefit/risk ratio. Risk analysis should be used to establish key objectives that need to be addressed by clinical data, or alternatively to justify why clinical data are not required (mainly for Class I devices). The risk analysis process should help the manufacturer to identify known (or reasonably foreseeable) hazards associated with the use of the device, and decide how best to investigate and estimate the risks associated with each hazard. The clinical data should then be used to establish the safety and effectiveness of the device under the intended use conditions, and to demonstrate that any of the residual risks are acceptable, when weighed against the benefits derived from use of the device. 

Active Implantable Medical Devices Directive 90/385 EEC Article 8 (Competent Authority Vigilance procedure), Annex II 3.1 (manufacturer s vigilance and reporting duties)... 

Possibilities for Enzymes in Implantable Fuel Cells There is significant and increasing demand for power supplies for implantable medical devices, including continuous glucose monitors for diabetic patients, thermal sensors for... 

The protection of microelectronics from the effects of humidity and corrosive environments presents especially demanding requirements on protective coatings and encapsulants. Silicone polymers, epoxies, and imide resins are among the materials that have been used for the encapsulation of microelectronics. The physiological environment to which implanted medical electronic devices are exposed poses an especially challenging protection problem. In this volume, Troyk et al. outline the demands placed on such systems in medical applications, and discuss the properties of a variety of silicone-based encapsulants. 

Humidity Testing of Silicone Polymers for Corrosion Control of Implanted Medical Electronic Prostheses... 

The lag between the time that nitinol, was first produced and the time it was used commercially in medical devices was due in part to the fear that nickel would leach from the metal and not be tolerable as a human implant. As it turns out, with a correct understanding of the surface electrochemistry and subsequent processing, a passivating surface layer can be induced by an anodizing process to form on the nitinol surface. It is comprised of titanium oxide approximately 20 mn thick. This layer actually acts as a barrier to prevent the electrochemical corrosion of the nitinol itself. Without an appreciation for the electrochemistry at its surface, nitinol would not be an FDA-approved biocompatible metal and an entire generation of medical devices would not have evolved. This is really a tribute to the understanding of surface electrochemistry within the context of implanted medical devices. 

Directive 90/385/EEC on active implantable medical devices ( AlMDs ) came into force on 1 January 1993 and is mandatory from 1 January 1995. This covers all powered implants or partial implants that are left in the human body, such as a heart pacemaker. 

Poly (ester-amide) elastomers were prepared by Pacetti et al. (1) and used with implantable medical devices. 

Katsarava et al. (4) prepared biodegradable hydrogels, (III), consisting of epoxy-containing poly(ester amides), which were used as implantable medical devices for delivery of biologically active agents. 

Title Degradable Polymeric Implantable Medical Devices with a Continuous Phase and Discrete Phase... 

Miniature batteries 100 mWh-2 Wh Electric watches, calculators, implanted medical devices... 

Power system. Previously, rechargeable nickel-cadmium cells were used in implant systems. More recently, the power systems of implantable medical electronic devices have become so small that a single AA size lithium primary cell can be used without recharging for more than 5 years. 

Microminiature drug delivery device. This is the heart of the implanted medication systems. The drug delivery device often consists of a diaphragm-operated infusion pump that supplies drug at a constant predetermined rate to the body. The pump is connected to the drug reservoir, which, in some cases, may be recharged when exhausted. Today, the available electronic components are so miniature that they can be implanted comfortably even in newborn babies. The pump can be programmed for a constant or variable basal infusion of medication with a repetitive period of from 1 hour to 60 days. By far the most frequently used basal period is 24 hours. A period of 28 days is available, particularly for the infusion of sex hormones to mimic the female menstrual cycle. 

Figure 13.3 Programmable implantable medication system (PIMS).

Programmable implantable medication systems find use in the treatment of diabetes, conditions of chronic pain, and Parkinson s and Alzheimer s diseases. Infusions of morphine can be programmed to deliver the drug when the intensity of pain is high. This reduces the chance of the patient developing tolerance to the opioid. Daily injection of insulin subcutaneously causes pain and sometimes infection in diabetic patients. A delivery system that has high accuracy of pumping... 

Hickey T, Kreutzer D, Burgess DJ, Moussy F. Dexamethasone/PLGA microspheres for continuous delivery of an anti-inflammatory drug for implantable medical devices. Biomaterials 2002, 23, 1649-1656. 

At the dawn of the 21st century, the invention, development, and use of hiomaterials has become big business in the United States and around the world. According to a 2001 report in Chemical and Engineering News, more than 10 million Americans now have at least one kind of implanted medical device, and national sales generated by the hiomaterials industry exceeds 50 billion per year. Industry analysts see an even larger future for the industry. For example, every year about 30,000 people die from liver failure while waiting for liver transplants, of which fewer than 3,000 become available every year. Modifications that would lead to acceptable liver substitutes would save the lives of many of these individuals. 

Advanced lithium batteries for implantable medical devices Mechanistic study of SVO cathode synthesis. J. Power Soc. 119-121 973-978. 

Holmes, C.F., P. Keister, and E.S. Takeuchi. 1987. High-rate lithium solid cathode battery for implantable medical devices. 1987. Prog. Batt. Solar Cells. 6 64—66. 

The development of implanted medical defibrillators required a high-rate, long-life battery system. In defibrillators, the CFx is used in combination with silver vanadium oxide (SVO) cathode materials [17]. A binary mixture of CFx and SVO are combined to form the cathode, giving the best features of SVO and CFx. Compared to CFx, the SVO has superior pulse current capability, but lower energy storage capability. The cell reactions are given in Equations 10.7 and 10.8. 

Low rate solid-electrolyte-based cells For instance, Li/I2 cells used primarily in implantable medical devices are well established. Another example is the developmental all-solid-state Li metal/phosphorous oxynitride (PON)/intercalation cathode cells conceived for use in microelectronic circuits. The PON is a glassy ceramic electrolyte which is stable to over 5 V [25],... 

The lithium/iodine-poly-(2-vinyl pyridine) system has some unique properties. Its major application is in implantable medical devices such as cardiac pacemakers, which operate at a thermostatted 37°C [28], The reaction is... 

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