Toward Non-invasive Neonatal Gas Monitoring with Plasma-based Spectroscopy

Transcutaneous gas monitoring of oxygen and carbon dioxide is animportant method for monitoring the oxygenation and ventilation inprematurely born infants. The amount of gas diffusing through theskin is very small and current technology rely on heating of theskin to increase the gas amount, where transcutaneous oxygenrequires the highest temperature. Heating damages the delicate skinof the infants and is a major concern among the nurses administeringthe treatment. In this thesis we have investigated a prototype and developedcomponents for a novel transcutaneous gas monitor capable ofperforming transcutaneous carbon dioxide measurements on adultswithout any external heating with a fast start-up time compared toconventional monitors. The technology is based on a microplasmasource developed at the Microsystems Technology department atUppsala university. The thesis has focused on producing three key components of theprototype. Firstly the controller board and radio frequency (RF)amplifier, previously two separate circuit boards, have beencombined into one. The design also incorporates improvementsregarding the power supply of the board, where a buck converterinstead of a linear regulator is used to step down most of thevoltage. This eliminates the need to use a heat sink to remove heatgenerated during voltage transformation. Secondly a sensor pad hasbeen developed from a silicone-based material which is soft,flexible and self-adhesive, allowing it to be placed anywhere on thepatient without tape or glue. And lastly techniques have beendeveloped to efficiently turn the raw data collected from the plasmasource into a usable carbon dioxide concentration signal. Though the plasma-based transcutaneous gas monitoring is yet farfrom clinical trials, the technology has shown promising results andit is deemed to be a viable alternative with better performance inpatient comfort, sensitivity and response time