A Fluorescent Thin Film-Based Miniaturized Transcutaneous Carbon Dioxide Monitor

Arterial blood gases, oxygen, carbon dioxide, and the potential of hydrogen are the key indicators of respiratory status and should be continuously monitored for patients whose respiratory vital signs may alter frequently and rapidly. The arterial partial pressure of oxygen and carbon dioxide can be estimated with transcutaneous monitoring, which measures the partial pressure of oxygen and carbon dioxide diffusing from the skin. However, requiring a heating element and a large, expensive bedside monitor are the limitations of the traditional transcutaneous blood gas monitors preventing continuous monitoring outside a clinical setting. Therefore, we propose a miniaturized fluorescent thin film-based prototype, envisioned as a first-of-its-kind continuous transcutaneous carbon dioxide monitoring wearable device. The computation principle relies on measuring the fluorescence intensity of a carbon dioxide-sensitive thin film. The prototype monitor estimates the partial pressure of carbon dioxide ranging from 0 to 75 mmHg, covering the clinically significant range, 35–45 mmHg for healthy humans. The prototype is designed with a small form factor on a 60 mm×55 mm printed circuit board and consumes 64.33 mW, suitable to be translated into a wearable device in further design stages.