Prediction of exhaled carbon dioxide concentration using a computer‐simulated person that included alveolar gas exchange

Abstract

Accurate prediction of inhaled CO 2 concentration and alveolar gas exchange efficiency would improve the prediction of CO 2 concentrations around the human body, which is essential for advanced ventilation design in buildings. We therefore, developed a computer-simulated person (CSP) that included a computational fluid dynamics approach. The CSP simulates metabolic heat production at the skin surface and carbon dioxide (CO 2 ) gas exchange at the alveoli during the transient breathing cycle. This makes it possible to predict the CO 2 distribution around the human body. The numerical model of the CO 2 gas exchange mechanism includes both the upper and lower airways and makes it possible to calculate the alveolar CO 2 partial pressure; this improves the prediction accuracy. We used the CSP to predict emission rates of metabolically generated CO 2 exhaled by a person and assumed that the tidal volume will be unconsciously reduced as a result of exposure to poor indoor air quality. A reduction in tidal volume resulted in a decrease in CO 2 emission rates of the same magnitude as was observed in our published experimental data. We also observed that the predicted inhaled CO 2 concentration depended on the flow pattern around the human body, as would be expected.

Coupled Eulerian Wall Film–Discrete Phase model for predicting respiratory droplet generation during a coughing event

“…The realistic trachea-bronchus model was created from CT scans, and details on the process are available in the previous study by Ito (Ito, 2016). This trachea-bronchus model, in combination with the nasal cavity, has been validated by our research group, providing reliable results in diverse research themes (C. Yoo & Ito, 2022;Kuga et al, 2021Kuga et al, , 2022Kuga et al, , 2023Murga et al, 2023;Khoa, Li, et al, 2023).…”