(L-454) Passive Intrathecal Drug Delivery System

Introduction:: Pain management is among the “Top Ten” recognized global healthcare issues. The constant demand for improved medical devices to manage pain derives from healthcare providers who treat patients with unresolved or chronic pain. Implantable drug delivery systems are considered one of the clinically preferred modes of treatments. However, many of the existing implantable devices for painkiller drug delivery are high cost and/or require biennial battery replacement. The proposed device is a passive intrathecal drug delivery implantable system, which will provide a controlled dose of painkiller. The level of medicine inside the device can be monitored through wireless electronics. The device is designed to be refillable, and operate without any internal batteries, to allow for long-term use without the need for a replacement

Materials and Methods:: The device design combines a series of concepts to achieve a cost-effective, tunable, and controlled delivery platform without battery power. The annular reservoir is a bellows surrounded by the dead volume of the implant’s outer shell filled with a noble gas. Infusion into the reservoir expands the bellows and compresses the gas. Careful engineering of the bellows geometry and material properties provides a quasi-linear pressure through compression of up to 75% of the reservoir volume over a period of 1-3 weeks. Adjustment of the catheter leading to the intrathecal space enables fine dosage control. Monitoring of bellows pressure will be conducted through an inductive wireless power transmission (IWPT) system, seen in Figure 2, that will enable radio transmission of pressure sensor data back to the handheld radiofrequency (RF) interrogator for patient self-monitoring and passive alerting. The outer shell will consist of a plastic radiolucent material such as polyetheretherketone (PEEK), to ensure that the pressure data can be transmitted without interference.

Results, Conclusions, and Discussions::

At the current stage of development, a preliminary design has been created for both the exterior and interior casing of the device and the onboard circuitry. The casing for the device is compartmentalized in such a way that pressure may be exerted in an appropriate manner without compromising the onboard electronics, the purity of the drug, or the safety of the patient. Seen as a divot on the top near the left of the diagram is the site where medicine may be refilled. Much of the rest of the “top” side of the device is dedicated to the electronics bay. The onboard electronics contain a two-antennae system which will convert radio waves from the external interrogator into alternating current (AC) power, then convert from AC to direct current (DC), before emitting an encoded radio signal. The frequency of this emitted radio signal is determined by a variable capacitor which functions as a pressure sensor, so the pressure can be read externally.
The theoretical pressure calculations, 3D modelling, and preliminary circuit analysis support the current design. Future work includes prototyping and testing the bellows reservoir, exploring MEMS manufacturing techniques for the creation of a pressure-sensitive capacitor, and optimizing the onboard circuitry.

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