Pulmonary artery, aortic and oesophageal pressure changes during high intensity treadmill exercise in the horse: a possible relation to exercise-induced pulmonary haemorrhage.

This research paper investigates how strenuous exercise affects certain physiological aspects in horses, specifically looking at changes in cell volume, pulmonary artery and aortic pressures, as well as the interaction of these with esophageal pressures. The paper hypothesizes that changes in esophageal pressure during exercise may contribute to exercise-induced pulmonary hemorrhage – a condition where a horse experiences bleeding in the lungs while engaged in high-intensity physical activity.

Research Method

• In the study, horses underwent acute treadmill exercise, which involved running at a speed of 10 meters per second on a 3 degree incline. The physiological effects of this intense exercise were measured.
• Various measurements were taken, including heart rate (HR), mean pulmonary artery pressure (PAP), mean aortic pressure (AP), and packed cell volume (PCV) which is a measure of blood viscosity or thickness. All these parameters showed a significant increase during the exercise compared to the resting state.
• To understand the effects of esophageal pressure changes on the other measured parameters, electronic subtraction of the esophageal pressure signal from PAP and AP signals was performed.
• The researchers observed exercise-induced pulmonary hemorrhage (EIPH) in three of the seven horses that participated in the exercise.

Key Findings

• The study found that the increase in PAP during exercise is more likely due to an increased heart rate and less likely due to changes in blood viscosity (PCV) or aortic pressure (AP).
• The study found no differences in heart rate, pulmonary artery pressure, aortic pressure, and packed cell volume between the horses that experienced EIPH and those that did not.
• The esophageal pressure changes during exercise caused significantly higher values in pulmonary artery and aortic pressures compared to resting pressures.
• The findings suggest that both pulmonary artery and aortic pressures are substantially affected by changes in esophageal pressure during strenuous exercise. These changes could potentially contribute to the occurrence of EIPH.

Possible Implications

• This research provides valuable insights into the physiologic mechanisms that might be involved in the development of exercise-induced pulmonary hemorrhage in horses.
• The findings could provide the necessary understanding for developing prevention strategies or interventions to reduce the incidence of EIPH in racehorses or working horses.
• Additional research is needed to further validate these findings and to deepen the understanding of the complex interplay between the different pressures experienced during intensive exercise.