Simulation of turbulent airflow using a CT based upper airway model of a racehorse.

This research utilized computer simulations to understand airflow dynamics in the upper respiratory tract of a racing horse. These findings will help in diagnosing and treating diseases that affect these parts of the respiratory system in horses, and may have implications for human health as well.

Developing a computational model for airflow

• The researchers aimed to create a computational model to understand the airflow in the upper respiratory system of a racehorse. This effort was driven by the lack of existent models which fully represented equine airways – due to their unique anatomy and high Reynolds number, which is a measure of flow behavior.
• To create the model, computed tomography (CT) scans of a thoroughbred racehorse’s airway were reconstructed. Different models were used for inhalation and exhalation, based on the change in size of the nasopharynx during these two phases of the breathing cycle.

Simulation and validation of airflow

• The researchers used the Reynolds-averaged Navier-Stokes equations to simulate isothermal airflow, while accounting for turbulence through the standard k-epsilon model.
• They applied transient pressure boundary conditions for the entire breathing cycle, obtained from previous studies on live horses, and solved the flow equations with a commercial finite volume solver.
• The model’s predicted flow rates were compared with measured flow rates to validate its accuracy.

Analyzing velocity, pressure, and turbulence characteristics

• After the validation, the research team conducted a detailed analysis of velocity, pressure, and turbulence inside the airway to better understand the dynamics of equine breathing.
• They discovered that inhalation velocities were higher, and the front and middle parts of the nasopharynx experienced the minimum intraluminal pressure.
• During exhalation, pressure in the soft palate was elevated compared to other parts of the upper breathing tract, like the larynx, epiglottis, and the remainder of the nasopharynx.

Implications for the health of racehorses and humans

• The observed dynamics provide important insight that can be used to diagnose and treat diseases affecting the soft palate and nasopharynx in horses.
• Specifically, high pressures and turbulent kinetic energy distribution suggest potential health issues that could affect horses’ respiratory function and performance.
• The findings may have implications beyond racehorses, potentially informing diagnosis and treatment of similar respiratory issues in humans as well.