Upper airway pressure was measured during maximal exercise in 10 Thoroughbred racehorses with naturally occurring upper airway obstruction. Left laryngeal hemiplegia and arytenoid chondropathy resulted in substantial increases (30-40 cm H2O) in inspiratory upper airway pressure (Pl), whereas complicated aryepiglottic entrapment and subepiglottic cysts produced only modest increases (15 cm H2O) in Pl. Uncomplicated aryepiglottic entrapment and grade IV pharyngeal lymphoid hyperplasia produced only slight increases (3-5 cm H2O). In general, surgical procedures restored airway pressures to within normal limits. Subtotal arytenoidectomy improved but did not normalize airway pressures in horses with arytenoid chondropathy. Pharyngeal lymphoid hyperplasia appeared to have little effect on upper airway function.

Upper airway pressure was measured with a nasotracheal catheter system and a portable pressure transducer in 10 normal horses during maximal exercise before and after left recurrent laryngeal neurectomy. Measurements were repeated 16 weeks after prosthetic laryngoplasty (5 horses) or subtotal arytenoidectomy (5 horses). During maximal exertion, prosthetic laryngoplasty was more effective than subtotal arytenoidectomy in reversing the increases in upper airway pressure that followed left recurrent laryngeal neurectomy.

Objectives-To evaluate laryngeal function using 3 diagnostic techniques: echolaryngography (EL), transnasal laryngoscopy (TNL), and laryngoscopy per os (LPO). Study Design-Prospective clinical study. Animals-Dogs with laryngeal paralysis (n ¼ 5) and control dogs (n ¼ 10); 5 age-and breedmatched dogs and 5 young, breed-matched dogs. Methods-Laryngeal function was evaluated in conscious dogs using EL. All examinations were recorded and evaluated by separate, blinded observers upon completion of the study. The methods were compared with a standard evaluation incorporating all clinical knowledge of the case (STD) using sensitivity, specificity, positive, and negative predictive values. Results-Three dogs with bilateral laryngeal paralysis requiring surgery were diagnosed as unilaterally affected or normal on EL. Three dogs had paradoxic motion on TNL and LPO, 2 of those were considered normal on EL, and 1 had no motion on EL. Paralysis was diagnosed in 1 agematched and 3 young control dogs on EL. LPO and TNL falsely diagnosed lack of arytenoid movement in 2 age-matched controls and 1 young control. Two age-matched and 1 young control dog were misdiagnosed as paralyzed with TNL and LPO. Discussion-Direct observation of the larynx allowed better evaluation of laryngeal function compared with EL. TNL did not require induction of anesthesia, but did not improve the ability to assess laryngeal function compared with LPO. Conclusions-EL was not as effective as direct observation of the larynx. TNL did not improve the evaluation of laryngeal function compared with LPO. Clinical Relevance-We use LPO combined with knowledge of the clinical history and physical examination to diagnose laryngeal paralysis in preference to EL and TNL. r

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