Evaluation of partial arytenoidectomy as a treatment for equine laryngeal hemiplegia.

The study evaluated the effectiveness of partial arytenoidectomy, a surgical procedure, as a treatment method for horses with laryngeal hemiplegia, a paralysis condition affecting the horse’s larynx. Despite not completely restoring the airway to normal function, results indicated that this treatment helped improve upper airway function in afflicted horses, particularly during exercise.

Research Methodology

• The researchers included six Standardbred horses in the study.
• Researchers surgically induced laryngeal hemiplegia in the horses, a condition in which one side of the larynx becomes paralyzed.
• The horses were assessed both at rest (Period A), and during exercise at two different levels – one corresponding to their maximum heart rate (Period C), and another at 75% of their maximum heart rate (Period B).
• Various measurements were taken, including the Peak Expiratory and Inspiratory Airflow Rate (PEF and PIF) and the Expiratory and Inspiratory trans-upper airway pressure (PUE and PUI).
• Researchers also measured Expiratory and Inspiratory Impedance (ZE and ZI) and derived indices from tidal breathing flow-volume loops (TBFVL), a measurement of airflow rate at different percentages of total lung capacity.
• Measurements were done before performing surgery (baseline), two weeks after the first surgical procedure (Left Recurrent Laryngeal Neurectomy, or LRLN), and 16 weeks after the second procedure (Left Partial Arytenoidectomy coupled with Bilateral Ventriculectomy, or ARYT).

Key Findings

• After the LRLN, some specific indices significantly increased, and others significantly decreased during exercise Periods B and C.
• 16 weeks after the ARYT, the index Z1 returned to baseline values during exercise Periods B and C.
• Although some parameters returned to baseline in exercise Period B, they remained significantly different from baseline during exercise Period C.
• After the ARYT, there was a noted approach to the baseline shape of tidal breathing flow-volume loops during Period C, suggesting improvement in upper airway function.
• However, some airflow limitation remained, even at near-maximal airflow rates.

Conclusion

• While a partial arytenoidectomy did not fully restore upper airway function, it did improve it significantly in horses with surgically-induced laryngeal hemiplegia, particularly while exercising.
• This suggests that partial arytenoidectomy is a promising treatment option for horses with failed laryngoplasty (surgical correction of the larynx) and arytenoid chondropathy (a laryngeal condition that affects racehorses).