Differential diagnosis of equine respiratory noises.

The research study analyzes the impact of different respiratory noises in horses, their causes, and implications for horse health. The focus is primarily on assessing horses before sale or in cases of performance issues.

Understanding Horse Anatomy and Respiratory Systems

• The study starts with an exploration of the anatomy of a horse’s upper respiratory tract. It visualizes a half-section of a horse’s head, providing details about the nasopharyngeal architecture, and highlighting areas like the mettle and turbinate bones.
• The horse’s airway and its transition during exercise is also discussed. It clarifies that the narrowest section of the airway at rest is the larynx with the greatest angulation at the pharynx.
• The study also elucidates that the horse is primarily a nose-breathing animal where the larynx is firmly positioned by the muscular palatopharyngeal ring and is disturbed only during swallowing when it descends into the oropharynx, which is known to take about one-tenth of a second.

Normal and Abnormal Respiratory Sounds

• The research article then transitions into the topic of respiratory sounds, especially during exercise. The paper suggests that a healthy horse doesn’t make audible respiratory sounds at rest and only produces a blowing expiratory sound when exercised at slower speeds.
• The paper also acknowledges that unfit or overweight horses often produce an inspiratory sound, which is loud and can be mistaken as a sign of disease. The phenomenon of “high blowing” is also explored where the sound produced varies greatly in pitch, believed to be the result of resonance in the false nostril’s cavity during expiration.

Production of Abnormal Sounds

• Finally, the study delves into the production of abnormal sounds. According to the study, normal respiratory sounds result from vibrations in the tissues of the respiratory tract and sudden changes in pressure in the moving air.
• It further explains that air flow in horses’ respiratory passages is largely laminar, wherein subsequent air layers slide smoothly over each other. However, any deformity in the wall disrupts this flow and causes turbulence. The turbulence causes sound and reduces the air flow underwater.