The effect of palatal dysfunction on measures of ventilation and gas exchange in Thoroughbred racehorses during high intensity exercise

REASON FOR PERFORMING STUDY: The effect of palatal instability (PI) on measures of ventilation and gas exchange is not well understood. OBJECTIVES: To assess to what degree different severities of naturally occurring palatal dysfunction affect ventilation and gas exchange during strenuous exercise. METHODS: A retrospective study was performed using data collected from 40 Thoroughbred racehorses diagnosed with naturally occurring dynamic palatal dysfunction during high speed treadmill exercise. Upper airway videoendoscopic recordings were made concurrently with measurements of ventilation and gas exchange. Three categories of soft palate dysfunction were formed: mild palatal instability; moderate to severe palatal instability; and dorsal displacement of the soft palate (DDSP). Minute ventilation, tidal volume, breathing frequency, end-tidal carbon dioxide and oxygen concentrations, oxygen consumption and carbon dioxide production were calculated during the last 10 s of the exercise test, when airway obstruction was at its worst. RESULTS: There was a trend for minute ventilation, tidal volume, oxygen consumption and carbon dioxide production to decrease with increasing degree of palatal dysfunction, although statistically significant differences were only seen with DDSP. End-tidal carbon dioxide increased and end-tidal oxygen decreased with increasing obstruction, with both parameters showing significant differences between mild PI and moderate to severe PI. CONCLUSIONS: The results suggest that PI has a negative effect on certain respiratory parameters, although this is not as great as that associated with DDSP. POTENTIAL RELEVANCE: Palatal instability may be detrimental to athletic performance even when progression to DDSP does not occur.K. Allen and S. Frankli