This project will develop a completely implantable telemetric pressure transducer for use in mice. Transgenic mice are increasingly important in research applications as the genetic foundations of many illnesses are being explored. Since genetic effects can be small, data acquisition that is continuous and physiological is becoming very important. Telemetric information from a conscious, normal mouse has led, for example, to the development of a mouse model for preeclampsia (28).
The specific aims of this Phase II effort are: a) miniaturization of the application specific integrated circuit (ASIC), b. development of pulse position modulation software, c. development of a graphical user interface (GUI) software, d. development of a high-fidelity pressure sensor sealed to atmosphere, and e. animal studies in murine rodents. The circuitry developed in Phase I is suitable for implantation into a rat. In Phase II the circuitry will be miniaturized and the battery will be replaced with an inductively powered capacitor. The prototype device will be implanted into dwarf rats in several studies. Pulse Position Modulation (PPM) will be used to conserve energy and permit miniaturization. PPM is the modulation of a pulse carrier wherein the value of each instantaneous sample of a modulating wave varies the position in time of a pulse relative to its unpopulated time of occurrence. In other words, the sensor data value that is acquired before transmission starts is sent to the receiver as a time interval between two transmissions pulses. This method of data transmission is the most energy efficient since the transmitter on time is very short. A graphical user interface will be developed to enable researchers to select the number of mice, period of data acquisition and frequencies desired. Temperature information is necessary for bridge compensation and will be available as another experimental parameter. A strain gauge pressure transducer completely sealed to atmosphere will permit high-fidelity measurement of arterial pressures. The development effort will seek to eliminate drift. Project Narrative we propose to develop a low mass implantable telemetric solid-state pressure sensor that is smaller than currently available devices, which can be used in small, multiply housed transgenic mice. Such a device would facilitate development of mouse models of human disease, especially those with a genetic component. Modifications of this device could be used to chronically measure uterine, bladder, eye and compartment pressures in humans.
