Ex vivo modeling of the airflow dynamics and two-and three-dimensional biomechanical effects of suture placements for prosthetic laryngoplasty in horses.

The research investigates the effect of different degrees of left arytenoid cartilage (LAC) abduction and suture placements on the air flow dynamics and biophysical properties in the larynx of horses, using cadaver models. The findings revealed that about 50% of the maximum LAC abduction force allows for optimal laryngeal airflow similar to that observed in galloping horses.

Understanding the Study and its Methods

• The study’s objective is to determine the optimal degree of left arytenoid cartilage (LAC) abduction that would facilitate laryngeal airflow akin to that in galloping horses.
• Furthermore, the research aimed to elucidate the two-dimensional (2D) and three-dimensional (3D) biomechanical impacts of prosthetic laryngoplasty on the movement of LAC, the airflow, and how sutures placed through different positions through the muscular process of the arytenoid cartilage (MPA) influenced these variables.
• Seven equine cadaver larynges were studied under experimental conditions that imitated the physiological conditions observed during respiration. The right arytenoid cartilage was maximally abducted, and inspiratory airflow was simulated by a vacuum.
• Varying forces of LAC abduction (from 0% to 100%) were applied via sutures passed through different directions – caudocranially or mediolaterally through the left MPA, and their effects measured through translaryngeal pressure, impedance, and airflow parameters.

Observations and Findings

• From the collected data, it was observed that translaryngeal pressure and impedance reduced, while airflow amplified rapidly at initial low abduction forces, before steadying and eventually plateauing at about 50% of the maximum abduction force.
• The most pronounced LAC motion occurred in the pitch direction, referred to as ‘rocking’.
• The suture position through the left MPA did not significantly influence the airflow dynamics, indicating that the applied abduction forces were more impactive.
• The sweet spot for airflow was found at around 50% of the maximum abduction force, which corresponds to a left arytenoid angle of approximately 30° and a left-to-right angle quotient of 0.79 to 0.84, enabling an airflow of about 61 ± 6.5 L/s.

Conclusions from the Study

• The ex-vivo study’s findings suggest that there is minimal benefit in applying LAC abduction forces greater than 50% as it did not significantly enhance the airflow beyond that observed at this force level.
• These findings provide insights that could aid surgical interventions, such as prosthetic laryngoplasty, in ensuring optimised post-surgical airflow in horses, mirroring that of galloping horses.