How transient laryngeal paralysis was modeled in dogs

Abstract

OBJECTIVE: To create a model of transient unilateral laryngeal paralysis (LP) that will allow the study of cricoarytenoideus dorsalis dysfunction and a method for quantification of varying degrees of LP in dogs. ANIMALS: 5 castrated male research Beagles. PROCEDURES: Between January and February 2018, dogs were anesthetized and instrumented with a laryngeal mask airway and a flexible endoscope to record the rima glottidis. The left or right recurrent laryngeal nerve (RLn) was localized using ultrasonography and electrical stimulation, then conduction blockade was induced with perineural lidocaine. The normalized glottal gap area (NGGA) was measured before and every 15 minutes after the block. Inspired 10% carbon dioxide (CO2) was administered for 1 minute at each sampling time. The inspiratory increase in NGGA (total and each side) was measured at peak inspiration. The change in hemi-NGGA for the control side versus the anesthetized side was evaluated with a mixed-effect model. RESULTS: During CO2 stimulation, the increase in inspiratory hemi-NGGA was consistently less (P < .001) for the treated side (-8% to 13%) versus the control side (49% to 82%). A compensatory increase (larger than at baseline) in the control hemi-NGGA was observed. The total NGGA remained unaffected. CLINICAL RELEVANCE: Unilateral local anesthesia of the RLn produced transient unilateral LP with a compensatory increase in the hemi-NGGA for the contralateral side. This model could facilitate the evaluation of respiratory dynamics, establishment of a grading system, and collection of other important information that is otherwise difficult to obtain in dogs with LP.