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.