The introduction and temporary implantation through the skin, e.g., transcutaneously, percutaneously and/or subcutaneously, of biosensors has become very common in the treatment of patients inflicted with or suffering from any one of many different types of conditions. These implantable sensors include those monitoring a given parameter that indicates a certain bodily condition, e.g., a patient's glucose level, or the actual state of a treatment, e.g., monitoring the concentration of a drug dispensed to the patient or a body substance influenced by the drug.
In recent years, a variety of temporarily implantable sensors have been developed for a range of medical applications for detecting and/or quantifying specific agents, e.g., analytes, in a patient's body fluid such as blood or interstitial fluid. Such analyte sensors may be fully or partially implanted below the epidermis in a blood vessel or in the subcutaneous tissue of a patient for direct contact with blood or other extra-cellular fluid, such as interstitial fluid, wherein such sensors can be used to obtain periodic and/or continuous analyte readings over a period of time.
Certain transcutaneous analyte sensors have an electrochemical configuration in which the implantable portion of these sensors includes exposed electrodes and chemistry that react with a target analyte. At an externally located proximal end of the sensor are exposed conductive contacts for electrical connection with a sensor control unit which is typically mountable on the skin of the patient. One common application of such analyte sensor systems is in the monitoring of glucose levels in diabetic patients. Such readings can be especially useful in monitoring and/or adjusting a treatment regimen which may include the regular and/or emergent administration of insulin to the patient.
A sensor insertion device or kit is typically provided with such analyte monitoring systems for inserting the sensor into a patient. The insertion kit includes an introducer which typically has a sharp, rigid structure adapted to support the sensor during its transcutaneous insertion. Some introducers are in the form of needles having a slotted or hollow configuration in which a distal portion of the sensor is slidably carried to the desired implantation site, e.g., subcutaneous site, after which the insertion needle can be slidably withdrawn from the implanted sensor. Often, the insertion kit also includes an insertion gun for automatically or semi-automatically driving the introducer and attached sensor to within the skin. Implantation of a sensor with such an insertion device typically involves using the insertion gun to drive the introducer and pre-loaded sensor into the skin of the patient. The introducer is retracted into the insertion gun, leaving the sensor implanted within the patient.
While such sensor insertion tools can greatly assist a user in effectively and efficiently implanting transcutaneous sensors, they are not without their drawbacks. As they are designed to be substantially automatic, the insertion guns tend to be mechanically complex, involving numerous static and moving parts. With the added complexity of such tools are significant costs in designing and fabricating them, contributing significantly to the overall cost of the sensor systems. In addition to the financial and manufacturing-related drawbacks, there are significant clinical consequences to using such transcutaneous sensor insertion tools.
The subcutaneous or other placement of such sensors, or any medical device, produces both short-term and longer-term biochemical and cellular responses which may lead to the development of a foreign body capsule around the implant. Consequently, this encapsulation may reduce the flux of an analyte to the sensor, i.e., may reduce the sensitivity or accuracy of the sensor function, often requiring numerous calibrations over the course of the sensor's implantation period. The extent of the immune response presented by implantable sensors, as well as the amount of pain and discomfort felt by the patient, are exacerbated by the size of the sensor introducer and/or the implantable portion of the sensor, often referred to as the sensor tail. With sensor introducers that carry the sensor within an interior or substantially interior space, there is naturally a limit on the extent to which the cross-sectional dimension of the introducer can be reduced.
Accordingly, it would be highly desirable to provide a sensor introducer and associated sensor design, and/or a combined assembly, which do not require a separate insertion tool for their transcutaneous insertion, thereby minimizing the number of components involved, and reducing mechanical complexity and manufacturing costs. It would be additionally advantageous if the respective and combined dimensions and configurations of the introducer and sensor were further reduced to minimize the trauma, pain and immune response to sensor insertion/implantation.