INTRODUCTION

The upper airway plays a crucial role in respiration, serving as the pathway for airflow to and from the lungs. Its integrity is vital for efficient respiratory function and overall health in equine athletes. Various factors, including anatomical variations and environmental conditions, significantly affect the assessment of airway abnormalities and their consequences on performance. It's important to recognize that performance context is essential to interpret the significance of findings accurately; for instance, recurrent laryngeal neuropathy may present as a minor issue for certain low-intensity equestrian events but could severely compromise performance in high-effort disciplines such as racing or jumping.

Notably, many performance-related issues associated with airway function are only apparent under dynamic conditions such as exercise; these problems may be undetectable during static evaluations where the horse is at rest. Thus, a comprehensive approach to airway assessment includes observing the horse during exercise and evaluating its respiratory response under stress. Furthermore, interventions aimed at improving respiratory conditions can inadvertently influence the functional relationship between the respiratory and digestive tracts, necessitating careful consideration of treatment strategies.

KEY POINTS

1. Upper airway dysfunction can stem from a myriad of causes including structural abnormalities, inflammation, and neurological deficits, all of which can seriously impede an athlete's performance if left unaddressed.

2. A thorough history of the horse's performance, along with a complete physical examination and resting endoscopic evaluation, are critical steps in accurately identifying abnormalities. The evaluation must include a detailed assessment of past incidents and any signs of respiratory distress or noise.

3. Advanced diagnostic techniques such as exercising endoscopy, ultrasound imaging, and radiography may be required for a more comprehensive assessment depending on the initial findings.

THE EVALUATION

Abnormal respiratory noises during exercise serve as significant indicators of potential airflow obstruction; the intensity of these sounds often correlates with the effort exerted by the horse. Initial evaluations should encompass:

• Gathering a thorough history and conducting a comprehensive physical examination, noting any previous respiratory issues.

• Palpating the larynx to check for asymmetry, muscle atrophy, or any surgical scars that may indicate prior interventions.

• Carrying out a resting endoscopic evaluation following standardized protocol to ensure consistency and reliability of findings.

Best practices for endoscopic examination:

• Employing a twitch for better control of the horse, minimizing movement that could hinder examination.

• Avoiding sedatives that might impair the horse's airway responses or interfere with the evaluation results.

• Inserting the endoscope quickly and correctly into the nasal cavity, without exceeding a length of 30-35 cm, to prevent trauma and ensure accurate visibility.

• Evaluating the pharyngeal vault and associated structures for:

  • Positioning of the epiglottis, ensuring it remains in a proper plane during respiration.

  • Symmetry and overall integrity of the arytenoids, looking out for any deviations or pathological signs indicating disorders.

RECURRENT LARYNGEAL NEUROPATHY (RLN)

Recurrent Laryngeal Neuropathy (RLN) is a prevalent condition among performance horses characterized by inspiratory noise that intensifies with increased exercise intensity. Diagnosis primarily involves:

• Evaluating for incomplete abduction of the arytenoids during resting endoscopy, which is critical for normal airflow.

• Catching potential dynamic collapse or displacement of the arytenoid cartilage during exercise, which can exacerbate respiratory distress.

• Distinguishing RLN from other similar disorders is crucial; a careful and thorough diagnosis helps to avoid misdiagnosis and inappropriate treatment plans.

TREATMENT STRATEGIES

Treatment should be tailored to directly address the primary clinical problems identified during evaluation:

• For racehorses, the emphasis is not solely on mitigating noise but rather on enhancing overall exercise tolerance and performance capabilities.

• Surgical interventions may include:

  • Ventriculocordectomy, which may require supplemental techniques to stabilize the airway effectively if performed alone.

  • Laryngoplasty is often indicated for RLN associated with arytenoid collapse; however, the success rate can be highly variable depending on the surgical technique employed.

• Continuous monitoring of horses post-surgery is crucial to ensure that optimal airway function is achieved and maintained.

ARYTENOID ABNORMALITIES (CHONDROPATHIES/DYSPLASIAS)

It is essential to differentiate between chondropathies and dysplasias:

• Dysplasias are typically congenital and remain structurally stable over time, whereas chondropathies tend to evolve and potentially worsen if left untreated.

• Diagnosis involves a thorough evaluation of structural abnormalities, often requiring advanced imaging techniques such as ultrasound or MRI for accurate confirmation.

• Management strategies must be focused on understanding how such deformities can affect performance, often leading to the consideration of surgical solutions.

EPIGLOTTIC ENTRAPMENTS

Common misconceptions surrounding epiglottic entrapments include:

• The belief that they are only prevalent in young racehorses. In reality, they can occur in any age group and may begin as intermittent issues that lead to more persistent obstructions over time.

• Surgical intervention might be necessary if the epiglottic entrapment leads to significant performance issues or consistent respiratory obstruction requiring timely action.

OTHER AIRWAY ABNORMALITIES

Various conditions such as pharyngeal collapse, epiglottic retroversion, and medial deviation of the aryepiglottic folds can significantly impact equine performance. As many of these conditions may escape detection at rest, it is crucial to conduct dynamic evaluations during exercise to accurately diagnose and address these abnormalities.

SUMMARY

Upper airway dysfunction poses severe implications for equine performance and necessitates meticulous diagnosis and personalized treatment approaches. The intricate nature of upper respiratory function, coupled with the nuanced interactions between various anatomical structures, complicates achieving full normalization of function, despite continuous advancements in veterinary understanding and technology.