Use of the forced oscillating airflow technique to measure the resistance of the equine upper airway: effects of laryngoventriculectomy and laryngoplasty.

The research observes the use of a forced oscillating airflow technique to study changes in total respiratory resistance (TRR) in horses. It particularly focuses on changes brought by laryngeal hemiplegia, a nerve-induced voice disorder, and the effects of certain surgical procedures, which include laryngoventriculectomy (Hobday operation) and laryngoplasty (tie-back operation).

Objective and Methodology

• The primary objective of the study was to detect changes in TRR (Total Respiratory Resistance) resulting from laryngeal hemiplegia.
• The research involved 8 ponies – 6 of them undergoing an operation involving division of the left recurrent laryngeal nerve and the other two retained as controls.
• Subsequent measurements were taken before two of the operated animals were subject to the Hobday operation (a laryngoventriculectomy), while laryngoplasty (a tie-back operation) was performed on another two animals.
• TRR measurements were made quarterly over a two-year period. Endoscopic examinations of the larynx accompanied these measurements.

Findings

• All ponies displayed a marked but regular variance in Total Respiratory Resistance over the two-year observation period.
• The surgical division of the nerve was observed to raise TRR in five out of six operated ponies.
• The Hobday operation reduced TRR levels in one pony and had no pronounced effect in the second one.
• The tie-back surgery contributed to decreased TRR in one pony while increasing it in another.
• Notably, one pony that had undergone the Hobday operation showed regeneration of the recurrent laryngeal nerve. Histological evidence of nerve regeneration was also found in another pony.

Conclusion

• The research suggested that nerve sectioning, Hobday operation, and tie-back operation affect the overall respiratory resistance in ponies.
• However, the specific impacts of these procedures on TRR varied among individuals. The research also provided some evidence of potential nerve regeneration post-operation.