Influence of Red Blood Cell Deformation and Clustering on CO Uptake
Blood flow supplies oxygen to and carries CO away
from the human body in the alveolar region of lungs. The gas
diffusing capacity, in particular the Carbon Monoxide (CO) uptake
rate, largely determines the lung efficiency. The pulmonary
diffusing capacity has been revealed to be impacted by various
factor such as flow rate, red blood cell (RBC) distribution, and
RBC shape. Uniform capillaries with diameter close to that of the
RBC have been found to induce large distortion of RBCs, while
non-uniform capillaries usually lead to clustering of RBCs near
contraction regions or capillary branches. Both distortion and
clustering of RBC introduce errors in morphometric estimates
of diffusing capacity. So far, the study of the influence of these two
factors are still limited at 2D static case and simple disk-shape
rigid RBC geometry. In this paper, we couple fluid-structure
interaction with gas diffusion problem. The RBCs motion and
deformation in capillary is simulated through the Immersed
Finite Element Method (IFEM). The gas diffusion into moving
and deforming RBCs under various geometries is studied. It is
found that when the RBCs are distorted, the CO flux across
membrane becomes nonuniform, leading to a larger diffusion
capacity. Our simulation also revealed a significant decrease of
diffusion capacity for clustered RBCs compared to uniformly
distributed RBCs. To our knowledge, this is the first paper that
simulate the dynamic process of gas diffusion on deformable
RBCs in capillary flow in three-dimension. By analyzing the
CO diffusion capacity dynamically in complex geometries and
flow conditions, our simulation may help compensate for error
in morphometric estimates and better interpret experimental
measurement.
Index Terms
Diffusion capacity, cell deformation, cell clustering, capillary flow.