Fukuoka, Japan—Researchers at Kyushu University and Institute of Science Tokyo have developed a new computational model that can simulate the transport of oxygen by red blood cells (RBCs) through tiny blood vessels—or capillaries—and their delivery to surrounding tissues. Published in the International Journal of Heat and Mass Transfer on April 27, 2026 , the study reveals that RBCs can naturally adjust the amount of oxygen released based on local requirements and help maintain a stable level of oxygen throughout the body.
Oxygen transport is one of the most essential processes for life. Every passing second, RBCs in the blood carry oxygen from the lungs through a network of microscopic channels and release it into tissues, where it is used to produce energy. The process consists of multiple overlapping steps, including blood flow, diffusion of oxygen, chemical reactions inside cells, and oxygen uptake by tissues. As these processes occur simultaneously and at the microscopic level, it has been difficult to understand the regulation of oxygen delivery in the body.
In this vein, Associate Professor Naoki Takeishi from Kyushu University's Faculty of Engineering along with collaborators from Institute of Science Tokyo, and Osaka University, developed a new mathematical model that combines these processes into a single framework.
"We applied equations that describe how oxygen moves, reacts, and is consumed, while also accounting for the motion and deformation of individual RBCs within blood flow," explains Takeishi.
Using this approach, the researchers were able to simulate oxygen transport across a complex network of capillaries in the body. They were also able to capture the movement of oxygen inside RBCs, the surrounding fluid, and into the tissues; all within a single system.
The findings revealed that even when RBCs are unevenly distributed in capillaries, they can regulate oxygen delivery in a way that maintains balanced oxygen levels in tissues. This occurs because oxygen release depends on local oxygen concentration: in low-oxygen regions, a greater amount of oxygen is released, while in areas with higher oxygen levels, the amount released is lower. This self-regulating behavior helps establish uniform tissue oxygenation.
The model also helped understand the variation in the flow behavior of blood, which also varied under similar conditions. Variations like movement of RBCs and deformation within branching capillary networks can influence flow resistance, indicating that blood flow properties are not always predictable from simple assumptions.
"Our model allows us to examine how multiple physical and chemical processes work together during oxygen transport," says Takeishi. "It provides a way to connect the behavior of individual RBCs with oxygen delivery at the tissue level."
The applications of this developed model are vast and could be applied beyond oxygen transport processes. It could help researchers better understand how different organs function and support the design of artificial systems for delivering oxygen or drugs within the body. As the modeling approach can be extended to general mass transfer problems, it may also prove useful in engineering fields involving transport of complex materials.
Looking ahead, the researchers aim to validate their work with experimental observations and apply their model to other complex biological processes, such as the transport and removal of metabolic waste in the brain.
