Laser fenestration of the dorsal pharyngeal recess does not correct experimentally induced dorsal nasopharyngeal collapse in horses.

Overview

• This research investigated whether laser fenestration surgery in the dorsal pharyngeal recess could improve breathing problems caused by dorsal nasopharyngeal collapse (NPC) in horses.
• The study found that experimentally induced NPC significantly worsened respiratory parameters and that the laser fenestration treatment did not improve these breathing impairments.

Background and Objective

• Dorsal nasopharyngeal collapse (NPC) is a condition where the upper airway in horses partially collapses, leading to impaired airflow and reduced respiratory performance.
• This study aimed to measure how inducing NPC experimentally affected key respiratory function markers in horses.
• It also evaluated whether laser fenestration of the dorsal pharyngeal recess—a surgical procedure intended to relieve airway obstruction—could restore normal respiratory function.

Methods

• Subjects: Six adult Standardbred horses were included; one horse naturally had NPC.
• Baseline measurements of respiratory performance were taken after an 8-week conditioning program, including:
• Maximum oxygen consumption (V̇Omax)
• Pharyngeal pressure
• Peak airflow rates
• Upper airway resistance
• Dynamic endoscopy videos during high-speed treadmill exercise (T1)
• Procedure to induce NPC: Bilateral glossopharyngeal neurectomy performed to cause dorsal NPC.
• Two weeks post-induction (T2), the respiratory and endoscopic assessments were repeated.
• Laser fenestration of the dorsal pharyngeal recess was then performed aiming to alleviate collapse.
• Final assessments were done three weeks after surgery (T3).
• Statistical analysis compared respiratory data between T1-T2, T2-T3, and T1-T3 using paired t-tests (significance at p < 0.05).
• Dynamic endoscopy videos were qualitatively graded for degree of collapse for visual assessment.

Results

• Dorsal NPC was successfully induced at a moderate to severe degree in five out of six horses.
• Respiratory function deteriorated significantly after NPC was induced:
• Maximum oxygen consumption (V̇Omax) dropped by 63.5 mL/kg/min (p = 0.006)
• Minute ventilation decreased by 78.8 L/min (p = 0.039)
• Peak expiratory flow rate decreased by 21.8 L/s (p = 0.013)
• Laser fenestration did not improve these parameters; instead, peak inspiratory flow rates decreased by 7.1 L/s (p = 0.03) after surgery.
• Subjective evaluation of endoscopy videos showed minor improvement in 2 out of 5 horses post-fenestration, but no consistent clinical benefit.
• In the single horse with naturally occurring NPC, the surgery led to a slight increase in V̇Omax (12.9 mL/kg/min) and some subjective improvement.

Conclusions

• Experimentally induced dorsal NPC significantly worsens respiratory performance in horses, confirming its detrimental effect on airway function.
• Laser fenestration of the dorsal pharyngeal recess, also known as laser salpingopharyngostomy in this context, did not improve respiratory parameters after NPC induction.
• This suggests that this laser surgery technique is not an effective treatment for dorsal NPC in horses with experimentally induced disease.
• While limited subjective improvement was observed in a naturally occurring case, the experimental findings do not support broader clinical use of this surgical method for NPC.
• Further research may be needed to explore alternative treatments or to evaluate laser fenestration in naturally occurring disease cases in a larger population.