Environmental conditions can have major influence on the lifetimes and reliability of active implantable medical devices (e.g., neurostimulators, cochlear implants, internal cardioverter defibrillators). These environmental conditions can range from those encountered by the device in processing and production to transportation and storage to actual operation. Although one might argue that the environmental conditions found in the first two situations are harsher than those of the third, failures that result from those situations are screened before implantation. If we assume that the active medical device is in perfect operational form at the time it is implanted, it will still experience a host of environmental conditions that can affect reliability. In fact, the ultimate goal of these medical devices is to restore the patient, wherever they may reside, to normal activities. A list of some environmental conditions that may be experienced by a device implanted in a representative patient is found in Table 1.

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