Endoscopic scoring of the tracheal septum in horses and its clinical relevance for the evaluation of lower airway health in horses.

This research article discusses the examination of the usefulness and reliability of endoscopic scoring of the tracheal septum in horses, used to assess lower airway disease. It was determined that although reliable, this method did not correlate with clinical, endoscopic, and cytological findings indicating airway inflammation or recurrent airway obstruction.

Investigation Methodology

• The study evaluated the variability of tracheal septum thickness scores (STS) due to the horse, observer, and time.
• STS distribution in a population of clinically normal horses was studied. The method explored correlations of STS with factors like age, gender, mucus accumulation, and cell differentials in bronchoalveolar lavage fluid and tracheobronchial secretions.
• The effects of altered pulmonary ventilation caused by drugs on STS were assessed.
• Lastly, the study compared the STS of horses suffering from recurrent airway obstruction (RAO) and that of clinically normal horses.

Findings and Results

• The study demonstrated excellent intra (within the same person) and satisfactory inter (between different people) observer agreement on STS.
• Contrary to the pre-defined hypothesis, established clinical, endoscopic, and cytological measures of lower airway inflammation such as mucus accumulation scores and airway neutrophilia did not show a correlation with STS.
• In horses aged 10 years or older, septum scores were significantly higher than in younger horses.
• The scores did not significantly differ between clinically normal horses and those affected by RAO, whether in a state of exacerbation or in remission.
• Horses exhibiting significantly increased breathing effort, induced by administering metacholine or lobeline hydrochloride, often showed marked differences (up to 1.9 scores), but the average of end-inspiratory and end-expiratory STS did not significantly deviate from the baseline STS.

Conclusion

• The scoring method is reproducible and reliable, but did not correlate the STS with clinical, endoscopic, and cytological findings that suggested RAO or inflammatory airway disease.