The present invention relates to implantable sensors, and more particularly to monitoring such sensors for proper performance. Even more particularly, the present invention relates to integrity tests that are performed on a regular basis in order to confirm proper sensor operation. A preferred sensor with which the present invention may be used is an implantable glucose sensor.
Implantable sensors are sensors adapted to be implanted within living tissue, e.g., within a living patient. The patient may comprise an animal or a human. Such implantable sensors are typically used to monitor one or more physiological parameters associated with the patient. For example, an implantable sensor may monitor a patient's blood or other body fluids for the presence or absence of a specific substance. Other implantable sensors may monitor the patient's body temperature. While a preferred sensor for use with the present invention comprises an implantable glucose sensor, or groups of glucose sensors, it is to be understood that the invention may be used with any type of implantable sensor(s). It is also to be understood that the principles underlying operation of an implantable sensor apply equally well to any sensor that is to remain unattended and submerged or immersed within a hostile environment, e.g., within a saline solution such as seawater, for a prolonged period of time. Thus, although the sensors described herein find particular applicability to sensors adapted to be implanted within living tissue, and the description is directed to such implantable sensors, the invention may also be applied to remote sensors of any kind that must be immersed unattended in a hostile environment for long periods of time.
In general, an implantable sensor may be used to provide valuable data that assists in diagnosing or treating an illness, or to help maintain or sustain a given level of physiological, chemical, or other activity or inactivity. In the case of glucose sensors, which are typically used with some type of insulin-delivery system in order to treat diabetics, the glucose sensors provide invaluable data needed to maintain the concentration of glucose within the patient at an acceptable level. Such glucose sensors must perform properly; otherwise, false data may be provided. Such false data (if acted upon) could result in the administration of an inappropriate amount of insulin, leading to death or serious injury. There is thus a critical need in the art for a sensor which is reliable and which can be monitored for proper function on a regular basis. Likewise, there is a need for a glucose sensor which must work properly within certain specific limits of accuracy.