BACKGROUND Tracheal collapse in horses is reportedly uncommon; however, American Miniature Horses are more commonly affected. There is no description of the tracheal luminal diameter of American Miniature Horses, making early detection of tracheal luminal narrowing difficult. OBJECTIVES To 1) describe radiographic tracheal luminal diameter in clinically normal American Miniature Horses, 2) report the prevalence of subclinical tracheal collapse in a population of American Miniature Horses, and 3) use tracheal videofluoroscopy to quantify variation in tracheal luminal diameter throughout the respiratory cycle in horses with no clinical respiratory disease. STUDY DESIGN Descriptive observational reference interval study. METHODS Thirty-four American Miniature Horses with no reported history of respiratory illness were recruited. Lateral cervical and thoracic radiographs were obtained in unsedated standing horses. Dynamic fluoroscopic images were obtained of the cervical and thoracic trachea throughout the respiratory cycle. Horses were then sedated as needed and tracheoscopy was performed. Twenty-nine horses were categorised as normal, and five horses were categorised as subclinically affected based on 25% or greater tracheal narrowing using tracheoscopy for visual assessment. Radiographic tracheal lumen to vertebral body measurements were obtained throughout the cervical and thoracic trachea. Maximum and minimum fluoroscopic tracheal diameter at each site throughout the respiratory cycle was recorded. RESULTS A mean, median, 95% confidence interval and bootstrapped 95% reference interval of radiographic tracheal diameter to vertebral body ratios were generated in normal horses. The prevalence of subclinical tracheal collapse in this population of American Miniature Horses is 14.7%. MAIN LIMITATIONS Bootstrapped reference range was generated from 29 horses. CONCLUSIONS Radiographic tracheal measurements and ratios of the tracheal diameter to vertebral body in the normal American Miniature Horse are described herein and can be used as a guideline when screening for tracheal disease in American Miniature Horses. The prevalence of subclinical tracheal collapse in American Miniature Horses may be higher than previously reported.

中文翻译：

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正常美国微型马的放射照相气管腔与椎骨的比率。

背景 据报道，马的气管塌陷并不常见。然而，美国微型马更常受到影响。美国微型马的气管管腔直径没有描述，使得早期发现气管管腔狭窄变得困难。目的 1) 描述临床上正常的美国小型马的影像学气管管腔直径，2) 报告美国小型马群中亚临床气管塌陷的患病率，以及 3) 使用气管视频透视来量化整个呼吸周期气管管腔直径的变化在没有临床呼吸道疾病的马中。研究设计 描述性观察参考区间研究。方法 招募了 34 匹没有呼吸道疾病史的美国小型马。在未镇静的站立马中获得侧位颈椎和胸椎 X 光片。在整个呼吸周期中获得颈部和胸部气管的动态透视图像。然后根据需要对马进行镇静并进行气管镜检查。29 匹马被归类为正常，5 匹马被归类为亚临床受影响，基于 25% 或更大的气管狭窄，使用气管镜进行视觉评估。在整个颈部和胸部气管中获得放射照相气管腔到椎体的测量值。记录整个呼吸周期中每个部位的最大和最小透视气管直径。结果平均值、中位数、在正常马匹中产生了放射照相气管直径与椎体比率的 95% 置信区间和自举的 95% 参考区间。在这群美国小型马中，亚临床气管塌陷的患病率为 14.7%。主要限制 Bootstrapped 参考范围是从 29 匹马生成的。结论本文描述了正常美国微型马的气管影像学测量值和气管直径与椎体的比率，并且可以用作美国微型马筛查气管疾病时的指南。美国微型马亚临床气管塌陷的患病率可能高于先前报道的。主要限制 Bootstrapped 参考范围是从 29 匹马生成的。结论本文描述了正常美国微型马的气管影像学测量值和气管直径与椎体的比率，并且可以用作美国微型马筛查气管疾病时的指南。美国微型马亚临床气管塌陷的患病率可能高于先前报道的。主要限制 Bootstrapped 参考范围是从 29 匹马生成的。结论本文描述了正常美国微型马的气管影像学测量值和气管直径与椎体的比率，并且可以用作美国微型马筛查气管疾病时的指南。美国微型马亚临床气管塌陷的患病率可能高于先前报道的。