The real-time monitoring of intravascular oxygen levels is important to accurately track the cardiopulmonary health of patients after cardiothoracic surgery. Existing methods use intravascular placement of glass fiber-optic catheters that pose risks of blood vessel damage, thrombosis and infection. Physical tethers to power supply systems can limit freedom of movement in the intensive care unit. In a new report now on Science Advances, Wei Lu and a team of international researchers in multidisciplinary research across the U.S., China, the Republic of Korea and Italy introduced a wireless, miniaturized and implantable optoelectronic catheter system. The device included optical components on the probe, encapsulated by soft biocompatible materials. The flexible, biocompatible construction of the probe represented key defining features to form a high-performance, patient-friendly oximeter that could monitor localized tissue oxygen, heart rate and respiratory activity in real time. The platform offered measurement accuracy and precision similarity to existing chemical standards.