Spectrum analysis of respiratory sounds in exercising horses with experimentally induced laryngeal hemiplegia or dorsal displacement of the soft palate

Objective-To record respiratory sounds in exercising horses and determine w hether spectrum analysis could be use to identify sounds specific for laryn geal hemiplegia (LH) and dorsal displacement of the soft palate (DDSP). Animals-5 Standardbred horses. Procedure-Respiratory sounds were recorded and pharyngeal pressure and stri de frequency were measured while horses exercised at speeds corresponding t o maximum heart rate, before and after induction of LH and DDSP. Results-When airway function was normal, expiratory sounds predominated and lasted throughout exhalation. After induction of LH, expiratory sounds wer e unaffected; however, all horses produced inspiratory sounds characterized by 3 frequency bands centered at approximately 0.3, 1.6, and 3.8 kHz. Afte r induction of DDSP, inspiratory sounds were unaffected, but a broad-freque ncy expiratory sound, characterized by rapid periodicity (rattling) was hea rd throughout expiration. This sound was not consis tently detected in all horses. Conclusions and Clinical Relevance-The technique used to record respiratory sounds was well tolerated by the horses, easy, and inexpensive. Spectrum a nalysis of respiratory sounds from exercising horses after experimental ind uction of LH or DDSP revealed unique sound patterns. If other conditions ca using airway obstruction are also associated with unique sound patterns, sp ectrum analysis of respiratory sounds may prove to be useful in the diagnos is of airway abnormalities in horses.