The displaced equine soft palate as a source of abnormal respiratory noise during expiration

Abstract

Summary Reasons for performing study: To develop the technique of respiratory sound analysis for the diagnosis of dorsal displacement of the equine soft palate. Objectives: To show that 1) the displaced soft palate can spontaneously vibrate in the presence of expiratory airflow; 2) the observed frequency of vibration can be detected in respiratory sound recordings; and 3) the frequency of vibrations measured in cadaveric specimens are similar to those obtained from audio spectra in exercising horses with DDSP. Methods: Palatal movements and respiratory sounds were recorded from artificially ventilated cadaveric heads. The fundamental mode of palate vibrations calculated from high‐speed videoendoscopic recordings was compared with frequencies detected in the audio spectra and with data collected from exercising horses with DDSP. Results: Palate vibrations occurred when air was blown through the trachea. The fundamental mode of vibrations was present in the audio spectra and was not significantly different from those recorded in vivo. Conclusions: Vibrations of the soft palate are the probable source of expiratory sounds recorded in horses with DDSP. Potential relevance: This study strengthens the case for the application of respiratory sound analysis in the diagnosis of DDSP in exercising horses.

Physiological measurements and prevalence of lower airway diseases in Trotters with dorsal displacement of the soft palate

“…Most affected horses make an abnormal noise during exhalation during a fast work (a ‘snoring’ noise). However, in approximately 30% of horses with DDSP, this noise is not reported (Franklin et al . 2004).…”

Dorsal displacement of the soft palate and palatal instability

“…In 70–80% (Derksen et al . 2001; Franklin et al . 2004) of cases, poor performance is associated with an expiratory respiratory noise, often described by trainers or jockeys as ‘snoring’, ‘gurgling’, ‘choking’ or ‘swallowing the tongue’.…”

“…Research efforts directed toward respiratory sound analysis (Derksen et al . 2001; Derksen 2003; Franklin et al . 2003, 2004) have shown promise, with DDSP horses usually producing a broad‐frequency expiratory sound, characterised by rapid periodicity (rattling) throughout expiration.…”

“…Low frequency fluttering of the caudal border of the palate is believed to be the source of the loud expiratory and inspiratory ‘gurgle’ or ‘snore’ reported in 70–80% of affected horses (Franklin et al . 2004).…”

“…2006b). Variability in the stiffness of the soft palate has been proposed as an explanation for why 20–30% of horses with DDSP do not make audible respiratory noises (Franklin et al . 2004).…”