Inclined running increases pulmonary haemorrhage in the Thoroughbred horse.

This research article analyzes the effects of inclined running on exercise-induced pulmonary haemorrhage (EIPH) in thoroughbred horses. The study finds that although inclined running reduces peak pulmonary arterial pressure, it intensifies EIPH severity, likely due to an altered ventilatory pattern.

Research Objectives and Methods

• The purpose of this study was to examine if inclined running would alter horses’ breathing patterns and thus increase the severity of EIPH, a condition characterized by bleeding in the lungs due to intense exercise.
• To conduct the study, six thoroughbred horses were run to their maximum tolerance on a level treadmill and an inclined treadmill (10% degree incline). The experiments were conducted in random order.
• Measurements were taken throughout each run, including pulmonary minute ventilation, arterial blood gases, and mean pulmonary arterial pressure (Ppa). EIPH severity was quantified 30 minutes post run using bronchoalveolar lavage (BAL), a method of examining the cells and fluids in the lower respiratory tract.

Research Findings

• The researchers found that time to fatigue was effectively the same in level and inclined runs.
• At the end of the exercise, horses running on an incline had a reduced breathing frequency and an increased tidal volume (the amount of air taken in during a normal breath) compared to level running.
• Despite these changes, there was no difference in end-exercise plasma lactate between the level and inclined trials – a measure often used to gauge an animal’s physical exertion level.
• Interestingly, peak Ppa, an intravascular measurement associated with EIPH, was reduced during the inclined run.
• Despite the reduced Ppa, the EIPH severity was significantly increased during the inclined running compared to level running, as measured by the red blood cells in BAL fluid.

Conclusions

• The findings indicate that even though inclined running lowers peak Ppa, it increases the severity of EIPH, likely due to an altered ventilation pattern (increased tidal volumes and associated intrapleural pressure changes).
• This suggests that extravascular factors play a significant role in the cause of EIPH. Understanding this will improve our knowledge of strenuous physical activity’s impacts on equine health and potentially guide the development of improved training and care protocols for horses.