Effect of dorsal displacement of the soft palate on ventilation and airflow during high-intensity exercise.

The study investigates the effects of a common respiratory condition in racehorses, dorsal displacement of the soft palate (DDSP), on their ventilation and airflow during high intensity exercise. The results confirm that DDSP causes an obstruction in the animal’s expiratory airflow, which subsequently hampers performance due to decreased oxygen uptake.

Explanation of Research

• The research centers around a prevalent issue among racehorses – dorsal displacement of the soft palate, or DDSP. It is a condition where the upper surface of the soft palate (part of the respiratory tract) wrongly positions itself over the epiglottis, potentially causing breathing problems.
• The study aims to understand how intermittent occurrences of DDSP affect the racehorse’s ventilation and airflow during strenuous exercise. Nine horses diagnosed with intermittent DDSP and known for underperforming in races were chosen for this investigation.
• The method employed included video-endoscopic recordings of the horse’s nasopharynx and larynx – areas directly affected by DSPP. The researchers simultaneously measured their respiratory gas exchange and airflow during high-speed treadmill exercise.

Key Findings

• The study found that in all the horses, DDSP led to a significant decrease in minute ventilation (VE), an essential measure of the respiratory system’s performance.
• It also led to a reduction in tidal volume (VT) – the volume of air moved into or out of the lungs in a single breath.
• Unlike VE and VT, the conditions seem not to affect the breathing frequency (f) – the number of breaths taken per minute.
• The researchers also observed a significant decrease in oxygen consumption (VO2) – a measure of the horsepower’s metabolic rate. Reduced VO2 implies diminished athletic capacity because less oxygen is available for muscle cells to produce energy for physical activity.
• Further, DDSP resulted in reduction of expiratory flow parameters, including peak expiratory flow (PEF), EF50, EF25 and EF125, indicating an obstruction in the airflow during expiration. Interestingly, there were no changes observed in the inspiratory flow – the flow of air during inhalation.

Conclusions

• The study confirms that naturally-occurring intermittent DDSP results in an obstructive condition limiting expiratory airflow.
• Researchers suspect that the consequent impairment of athletic performance could be caused, at least partly, by the related decrease in oxygen uptake. Hence, the study sheds light on why racehorses with DDSP may underperform due to the condition’s direct effect on their respiration and metabolism during high-intensity activities.