Dynamic Modeling of Carbon Dioxide Transport through the Skin Using a Capnometry Wristband

Area of Science:

• Biomedical Engineering
• Physiological Monitoring
• Optical Sensing Technology

Background:

• Home monitoring of patients requires non-invasive and continuous physiological measurements.
• Capnometry, measuring carbon dioxide (CO2) levels, is crucial for assessing respiratory function.
• Existing capnometry devices may not be suitable for convenient, long-term at-home use.

Purpose of the Study:

• To develop and validate a novel capnometry wristband for real-time monitoring of blood CO2 concentration.
• To model the temporal dynamics of CO2 exchange between blood and a novel sensor architecture.
• To assess the feasibility of using a Kalman filter for accurate CO2 estimation in a wearable device.

Main Methods:

• Proposed a new wristband architecture integrating non-dispersive infrared (NDIR) sensing with an open chamber and airflow.
• Developed a multi-compartment model (blood, skin, measurement cell, collection cell) for CO2 transport using convection-diffusion equations.
• Implemented a state-space representation with a Markovian model and an augmented system incorporating a first-order autoregressive model.
• Utilized a Kalman filter for recursive estimation of blood CO2 concentration.

Main Results:

• A mathematical model was established to describe CO2 dynamics within the wristband's collection cell.
• The Kalman filter successfully estimated blood CO2 concentration recursively over time.
• Simulations based on clinical data demonstrated the feasibility of the proposed capnometry wristband concept.
• The system showed potential for real-time monitoring of arterial CO2 blood pressure.

Conclusions:

• The developed capnometry wristband architecture and Kalman filtering approach show promise for non-invasive, real-time CO2 monitoring.
• This technology could enable effective remote patient management and improve healthcare accessibility.
• Further clinical validation is warranted to confirm the performance and reliability of the device in diverse patient populations.