Non-Invasive Clip-On System for Blood Oxygenation Measurement in Extracorporeal Circulation

This paper presents the development and evaluation of a novel tube clip-on system for non-invasive blood oxygenation measurement, designed to overcome the limitations of existing in-line sensors used during Extracorporeal Membrane Oxygenation (ECMO) therapy. The system leverages differential light absorption by oxygenated and deoxygenated hemoglobin, employing light spectroscopy principles to determine oxygen saturation levels. A comprehensive optical path analysis, utilizing Monte Carlo simulations, was conducted to optimize sensor design, considering factors such as light scattering and tube geometry. The developed system features a sensor sheath with a sliding lock mechanism, accommodating multiple LEDs and photodiodes strategically positioned around the blood tubing. An electronic mainboard, incorporating an ADPD1080 photometric front-end and an STM32F303 microcontroller, facilitates precise photometric measurements and data acquisition. The system was tested in a closed-loop blood circuit, with oxygen saturation levels controlled using an Oxygenator and monitored using a Terumo CDI500 reference sensor and ABL800 Flex blood gas analyzer. Experimental results were compared with simulation predictions, demonstrating a strong correlation in the dependency on oxygen saturation, despite discrepancies in absolute values. However, the dependency on detector angle position was less clear. The system shows potential for reliable, non-invasive blood oxygenation monitoring in ECMO applications, offering advantages in terms of ease of use, reduced invasiveness, and applicability to existing ECMO circuits even after onset of therapy. Further research will focus on refining the sensor design and addressing the observed dependencies on detector angle and blood flow rate.