Towards accurate transcutaneous CO₂ sensing: A behavioral model using time-correlated single photon counting

Area of Science:

• Biomedical Engineering
• Optical Sensing Technologies

Background:

• Transcutaneous CO2 sensing is crucial for assessing ventilation effectiveness.
• Existing methods may have limitations in accuracy and real-time monitoring.

Purpose of the Study:

• To develop a behavioral model for estimating rapid fluorescence signal lifetimes.
• To enhance the accuracy and applicability of lifetime-based transcutaneous CO2 sensing systems.

Main Methods:

• Implemented a model simulating the complete optical and electronic signal chain.
• Utilized time-correlated single photon counting (TCSPC) and silicon photomultipliers (SiPMs).
• Incorporated nonidealities like dark counts, afterpulsing, crosstalk, and excitation leakage.

Main Results:

• Achieved 86%-93% accuracy in recovering fluorescence lifetimes at ambient CO2 levels.
• Successfully resolved fluorescence lifetimes as short as 3.5 ns.
• Identified performance decrease at shorter lifetimes due to noise and reduced decay slope.

Conclusions:

• The developed model accurately estimates fluorescence lifetimes for CO2 sensing.
• The model shows potential for guiding the development of improved CO2 monitoring devices.
• Findings support advancements in clinical and ambulatory CO2 monitoring applications.