Propofol in Exhaled Breath: Real-time Detection by Surface Acoustic Wave Sensors

DESCRIPTION (provided by applicant): Propofol endures as the most popular intravenous (IV) anesthetic due to several favorable characteristics. Anesthesia personnel customarily measure the concentrations in breath of many agents used during surgery including: molecular oxygen to prevent hypoxia, carbon dioxide to assure placement of an endotracheal tube in the trachea and adequate ventilation, and anesthetics (e.g., desflurane, nitrous oxide) to maintain the appropriate level of consciousness /depth of anesthesia. Recently, several independent research teams have demonstrated that patients receiving IV propofol eliminate a fraction of this anesthetic in the breath. Also, the concentration of propofol in breath correlates to and is therefore predictive ofits free blood concentration. Therefore, the possibility exists to determin and manipulate the blood concentration of propofol using real-time, point-of-care measurement of exhaled propofol levels to guide its dosing. This ability will be similar to techniques already employed for volatile anesthetics and will improve patient safety. Unfortunately, the current research tools (e.g., proton transfer reaction-mass spectroscopy [PTR-MS], gas chromatography- mass spectroscopy [GC-MS]) used to measure propofol inbreath consists of sensitive, large, very expensive equipment that requires skilled, personnel to operate. Clearly, the development of novel technology that is small, robust, reliable, and easily operated for measuring exhaled propofol levels is a prerequisite for clinical acceptance. The goal of this grant proposal is to design, build, and test a prototype device to measure exhaled propofol. The innovation of this application is leveraging previous development by the Department of Defense by adapting polymer coated surface acoustic wave (SAW) technology to detect propofol at clinically relevant concentrations. To this end, the following specific aims will be achieved: Aim 1: Design and build a SAW detector with improved circuitry, miniature valving, an improved collection tubing to patient, and CO2-gated collection (4 months). Aim 2: Measure and compare propofol concentrations in exhaled breath (using SAW and conventional GC- MS) to those in plasma (using UPLC) in human patients (n=15) anesthetized with propofol. (8 months) The short term objective of Xhale, Inc. is to research and develop these devices for later introduction into the US market, projected to exceed 341 million by 2013. PUBLIC HEALTH RELEVANCE: Propofol endures as a commonly usedintravenous anesthetic and has recently been demonstrated to emanate from the lung in concentrations proportionate to blood concentrations. The goal of this project is to design, build, and test a prototype device to measure exhaled propofol in order to estimate human blood concentrations in real-time and to improve the safety of patients anesthetized with this agent.