Relationship of pulmonary arterial pressure to pulmonary haemorrhage in exercising horses.

This study investigates the correlation between pulmonary arterial pressure and exercise-induced pulmonary haemorrhage (bleeding in the lungs due to strenuous activity) in horses. It finds that there exists a threshold of pulmonary arterial pressure after which haemorrhage occurs in the lungs, particularly during high-speed sprint exercises.

Introduction

• This research targets understanding Exercise-induced pulmonary haemorrhage (EIPH) in horses, a condition known to cause blood in the airways following intensive workouts and which results from stress issues in the pulmonary capillaries.

Objective and Methodology

• The main objective of the study is to identify a threshold value for the transmural pulmonary arterial pressure at which haemorrhage or bleeding in the lungs happens in horses during exercise.
• This experiment took five geldings between the ages of 4 to 14 years and made them run at random sequences once every two weeks at one of four predetermined speeds: 9, 11, 13, or 15 m/s. A control day was also administered where no running took place.
• During each running session, vital details like the horse’s heart rate, oesophageal pressure, and pulmonary arterial pressure were recorded throughout.
• An estimated calculation of transmural pulmonary arterial pressure was conducted using an electronic method to subtract the oesophageal pressure from the intravascular pulmonary arterial pressure.
• After one hour of each running period, bronchoalveolar lavage was performed and the red and white blood cell count in the fluid was quantified.

Results

• The results showed no significant difference in the red cell counts in the lavage fluid when horses ran at speeds of 9, 11, and 13 m/s when compared to the control group. However, after running at 15 m/s, red cell counts showed a significant increase.
• White cell counts did not show any significant difference from control group values regardless of the speed of the horse.
• Analysis of the red cell count in comparison to the transmural pulmonary arterial pressure showed that haemorrhage occurs at roughly 95 mmHg. Red cell lysis in the lavage fluid was also noticeable at transmural pulmonary arterial pressures above 90 mmHg.

Conclusion

• The research concludes that in exercising horses, there is a specific threshold of pulmonary arterial pressure above which lung haemorrhage occurs. This threshold often gets crossed during high speed sprint exercises in horses.