Dynamic tracheal collapse as a cause of exercise intolerance in a thoroughbred.

This research investigates a case of exercise intolerance in a young racehorse due to dynamic tracheal collapse, demonstrating the importance of using dynamic tracheal videoendoscopy for accurate diagnosis and treatment of such conditions.

Overview of the Case

• The paper presents a case study of a 2-year-old Thoroughbred filly admitted to the hospital for evaluation of exercise intolerance; a condition where the horse had difficulty in performing physical activity.
• Initial videoendoscopic evaluation while the horse was standing, discovered a tracheal defect 100cm away from the external nares (nostrils) and right arytenoid paresis, a paralysis or weakness of the muscles controlling the arytenoid cartilage of the larynx (voice box).
• As a response to these findings, a right prosthetic laryngoplasty surgery was performed.

Post-Surgery Discoveries

• Post-surgery analysis with a videoendoscope revealed minimal movement (abduction) of the affected arytenoid cartilage.
• While the horse was exercising, the dynamic videoendoscopy showed the right arytenoid to be fixed in a submaximal position, with no evidence of collapse into the airway.
• However, placing the endoscope in the mid-cervical tracheal region (middle-neck region of the windpipe) during exercise revealed marked tracheal collapse.

Significance of Findings

• The results suggest that tracheal collapse can severely limit the athletic capability of horses.
• The treatment of such conditions may depend on the cause, the extent of the trachea involved, and the accessibility of the affected part of the windpipe.
• Thus, dynamic tracheal videoendoscopy can be an important tool in diagnosing exercise intolerance in cases where no discernible causes are found from resting or nasopharynx-focused videoendoscopic evaluations.