Observations on respiratory flow strategies during and after intense treadmill exercise to fatigue in thoroughbred racehorses.

The research observes the different types of breaths that a racehorse takes during and after intense treadmill exercise, with specific emphasis on ‘big respiratory cycles’ or BRCs. It further examines whether such breath types are a normal feature of a horse’s ventilation after intense exercise and how they are associated with the respiratory frequency.

Objective and Methodology

• The goal of this research was to investigate the occurrence of distinct breath types during and after intense treadmill exercise in thoroughbred racehorses. It also tested the hypothesis that the frequency of larger breaths (BRCs) is a function of respiratory frequency.
• For this study, six trained and clinically sound thoroughbred horses were used. They were exercised on a treadmill that was set at a 10% slope. A Quadflow mask was used to measure breath-by-breath pulmonary ventilation continuously during exercise and recovery.

Results Observed

• During the exercise, five different breath types were identified – normal monophasic, normal biphasic, deglutition, effort pause, or large breaths.
• When the horses exercised at a speed of 10 m/sec, the number of large breaths recorded was significantly correlated to the respiratory frequency, lending confirmation to the study hypothesis.
• After 120 sec post-exercise, two distinct types of breaths could be seen – large and normal monophasic breaths.

Conclusions Drawn

• The study concludes that ‘big respiratory cycle’ (BRC) type breaths are normal during both intense exercise and recovery stages in horses. However, the prevalence of these can vary based on respiratory frequency and the individual horse.
• The research further concludes that there is a significant correlation between the occurrence of BRCs and the partial end-tidal carbon dioxide (PECO2), which might throw light on the mechanism driving BRCs.
• The results also demonstrate a shift from high flow rates and limited tidal volumes during intense exercise, to high tidal volumes and progressively decreasing flow rates during recovery. The understanding of this could potentially have clinical relevance.
• Understanding the breath types and the physiological mechanisms driving each type is crucial in diagnosing any respiratory diseases or dysfunctions in horses. It also is important for accurate results in pulmonary function testing.