Predicting how therapeutic liquid plugs move through lungs

When therapeutic fluids are injected into an airway, they form a liquid plug that moves through the respiratory system. To optimally distribute these therapies, clinicians need to be able to predict how a liquid plug will split at branches in the lungs, known as bifurcations. However, most simulations of liquid plug splitting use simplified models of lung structures which exclude these bifurcations.

Lv et al. simulated the transport and splitting of liquid plugs using a realistic bifurcation model of human airways and the chemical-potential lattice Boltzmann method, a technique for simulating multiphase flows. They incorporated complicated airway geometries, gravitational orientation effects, and liquid film interactions to increase the accuracy of the simulation.

The authors found that gravitational orientation and the driving force of a liquid plug determines whether a plug splits symmetrically or asymmetrically at a bifurcation. For example, as the driving force of the plug decreases, the effect of gravity increases, which causes more of the plug to enter a lower branch.

“Our work enhances the mechanistic understanding of how liquid plugs split and move through lung bifurcations, which is critical in surfactant replacement therapy, partial liquid ventilation, and targeted drug delivery,” said author Binghai Wen. “By offering a more realistic simulation framework, this research contributes to optimizing therapeutic strategies and improving drug delivery uniformity in clinical pulmonary treatments.”

This framework can be used in experimental and clinical settings to evaluate how liquid viscosity, airway geometry, patient posture, and other parameters affect drug distribution. The authors plan to extend the model from two to three dimensions and incorporate deformable airway walls to better simulate specific lung diseases, such as acute respiratory distress syndrome or chronic obstructive pulmonary disease.

Source: “Liquid plug transport and splitting in bifurcated airways by lattice Boltzmann method,” by Qianyu Lv, Lili Lan, Bing He, and Binghai Wen, Physics of Fluids (2025). The article can be accessed at https://doi.org/10.1063/5.0280889 .