This invention relates to telemetered subcutaneous sensor devices and, in particular embodiments, to devices and methods for wireless communication between an implantable subcutaneous sensor set at a selected insertion site within the body of a user and a remotely located characteristic monitor.
Over the years, a variety of implantable electrochemical sensors have been developed for detecting and/or quantifying specific agents or compositions in a patient""s blood. For instance, glucose sensors have been developed for use in obtaining an indication of blood glucose levels in a diabetic patient. Such readings are useful in monitoring and/or adjusting a treatment regimen which typically includes the regular administration of insulin to the patient. Thus, blood glucose readings improve medical therapies with semi-automated medication infusion pumps of the external type, as generally described in U.S. Pat. Nos. 4,562,751; 4,678,408; and 4,685,903; or automated implantable medication infusion pumps, as generally described in U.S. Pat. No. 4,573,994, which are herein incorporated by reference.
Generally, small and flexible electrochemical sensors can be used to obtain periodic readings over an extended period of time. In one form, flexible subcutaneous sensors are constructed in accordance with thin film mask techniques in which an elongated sensor includes thin film conductive elements encased between flexible insulative layers of polyimide sheets or similar material. Such thin film sensors typically include a plurality of exposed electrodes at one end for subcutaneous placement with a user""s interstitial fluid, blood, or the like, and a corresponding exposed plurality of conductive contacts at another end for convenient external electrical connection with a suitable monitoring device through a wire or cable. Typical thin film sensors are described in commonly assigned U.S. Pat. Nos. 5,390,671; 5,391,250; 5,482,473; and 5,586,553 which are incorporated by reference herein. See also U.S. Pat. No. 5,299,571.
Drawbacks to the use of implantable sensors arise from the use of a wired connection between the implantable sensor set and the monitor. The use of the wire or cable is an additional inconvenience to users that already utilize an external infusion pump that includes an infusion insertion set and tube to infuse the medication. Also, the preferred site for some sensing device may be inconvenient for connection by wire to a characteristic monitor. For implantable pumps, the wire or cable negates the very benefit of having an internal device without external wires or cables. For Type 2 diabetics, who do not necessarily need or use an infusion pump, the use of a cable is seen as an inconvenience that may inhibit use of the device. In addition, the use of a wire or cable limits a user""s ability to position the monitor, since it can be placed no further away than the ultimate length of the wire or cable. Thus, the user must normally wear the monitor, which can be problematic. For example, removal of the monitor for sleeping can be difficult, since a user would tend to become xe2x80x9ctangledxe2x80x9d in the wire or cable, between the sensor and the monitor, during the normal tossing and turning that occurs during sleep. Furthermore, the more connections the user must deal with (e.g., infusion pump and catheter and/or monitor with wire to sensor), the more complicated it is to use the devices, and the less likely the user will maintain compliance with the medical regimen due to perceived and actual difficulties with all of the wires and cables.
It is an object of an embodiment of the present invention to provide an improved telemetered implantable sensor set (such as a subcutaneous or percutaneous sensor) and monitor connection device, which obviates for practical purposes, the above mentioned limitations.
According to an embodiment of the invention, a telemetered characteristic monitor system includes a remotely located data receiving device, a sensor for producing signal indicative of a characteristic of a user, and a transmitter device. In preferred embodiments, the transmitter device includes a housing, a sensor connector, a processor, and a transmitter. A potentiostat within the transmitter device may be coupled to the sensor connector and applies power to the sensor. The sensor connector receives the produced signals from the sensor. The processor is coupled to the sensor connector and processes the signals from the sensor for delivery to the remotely located data receiving device. The transmitter is coupled to the processor for wirelessly transmitting the processed signals to the remotely located data receiving device. In preferred embodiments, the data receiving device is a characteristic monitor. However, in other embodiments, the data receiving device is a data receiver that provides data to another device, an RF programmer, a medication delivery device (such as an infusion pump), or the like.
In particular embodiments, the transmitter of the transmitter device transmits the processed signals by radio frequencies. In other embodiments, the sensor may be implanted in and/or through subcutaneous, dermal, sub-dermal, intra-peritoneal or peritoneal tissue, and the sensor connector of the transmitter device includes a cable that is connected to the sensor. Also, the implantable sensor can be configured for a wired connection to a characteristic monitor, and the sensor connector of the transmitter device is formed to connect to the configured implantable sensor. Still further embodiments of the transmitter device include a receiver to receive data and instructions from the characteristic monitor, or the like.
Embodiments of the transmitter device (when used with a subcutaneous or percutaneous sensor) may include a bio-compatible adhesive to secure the housing to a skin surface of the user. Preferably, the housing of the transmitter device is less than about 3.0 inches in diameter by 0.5 inches thick. In addition, the housing is resistant to fluids when immersed in a fluid, operable in a temperature range of 0xc2x0 C. to 50xc2x0 C., and has an operable life of at least 3 months. If the sensor is fully implanted, the transmitter that is connected to the sensor may be secured by sutures, sewing rings, or the like.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, various features of embodiments of the invention.