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

OBJECTIVE: To quantify the impact of experimentally induced dorsal nasopharyngeal collapse (NPC) on respiratory performance parameters and assess the efficacy of laser fenestration of the dorsal pharyngeal recess as a treatment option for experimentally induced NPC. STUDY DESIGN: Experimental interventional study. ANIMALS: Six adult Standardbreds (one with naturally occurring disease). METHODS: After an 8 week conditioning program, baseline parameters (V̇O2max, pharyngeal pressure, peak airflows, upper airway resistance) and dynamic endoscopy videos were collected in a high-speed treadmill test (T1). Dorsal NPC was induced via bilateral glossopharyngeal neurectomy, followed by data collection 2 weeks later (T2). Laser fenestration of the dorsal pharyngeal recess was then performed, followed by final data collection 3 weeks later (T3). Respiratory performance parameters for T1-T2, T2-T3, and T1-T3 were compared using paired t-test (p < .05) to evaluate the impact of NPC and efficacy of surgery. Dynamic endoscopy videos were subjectively graded and compared. RESULTS: Moderate to severe dorsal NPC was successfully induced in five horses, with subjective improvement seen on dynamic endoscopy in 2/5 horses after fenestration. After NPC induction, V̇O2max, minute ventilation, and peak expiratory flow rates decreased by 63.5 mL/kg/min (p = .006), 78.8 L/min (p = .039) and 21.8 L/s (p = .013) respectively. Following fenestration, peak inspiratory flow rates decreased by 7.1 L/s (p = .03). In the naturally occurring case, V̇O2max increased by 12.9 mL/kg/min post-fenestration with subjective improvement in the degree of collapse. CONCLUSION: Respiratory performance parameters worsened following NPC induction in comparison with the baseline and did not improve following laser fenestration. CLINICAL SIGNIFICANCE: This experimental model did not support clinical application of laser salpingopharyngostomy to treat NPC.