Pulmonary vascular pressures of exercising thoroughbred horses with and without endoscopic evidence of EIPH.

The research investigates exercise-induced pulmonary hemorrhage (EIPH) in racehorses, comparing pulmonary pressures in healthy horses with and without endoscopically detected fresh blood in their trachea after exertion. The study found that the increase in heart rate and pulmonary vascular pressures during exercise was similar between horses with EIPH and those without, indicating that this condition does not significantly affect these parameters during exertion.

Research Objective and Methods

• The objective of the study was to observe the difference in pulmonary vascular pressures in able-bodied racehorses displaying signs of EIPH and those without, using endoscopic examination to detect the presence of fresh blood in the trachea post-exercise as an indicator of EIPH.
• The subjects were Thoroughbred horses, with the trachea, nasopharynx, and larynx examined using an endoscope about an hour post-exercise. The horses undertook treadmill exercise at 14.5 m/s at a 5% incline, designed to max out their heart rate.
• The researchers observed 7 horses that exhibited signs of fresh blood in their trachea post-exercise, compared to 8 other horses that didn’t show these symptoms. They monitored these horses over 12 to 16 weeks.

Research Findings

• At rest, there was no significant difference in the heart rates or right heart and pulmonary vascular pressures of the horses with and without observed EIPH.
• During exercise, both groups showed a significant increase in heart rate and pulmonary pressures, which demonstrates the normal physiological response to increasing physical demands.
• No significant differences in heart rate, right atrial, and pulmonary vascular pressures were discernible between the EIPH-positive and EIPH-negative horse groups.

Conclusion of the Study

• The study implies that the magnitude of exercise-induced right atrial and pulmonary arterial, capillary, and venous hypertension in healthy horses with evidence of EIPH is equivalent to that in healthy EIPH-negative horses under similar exertional circumstances.
• This indicates that, despite the presence of EIPH, heart and pulmonary system functions remain comparably unaffected during exertion, suggesting physiological adjustments to accommodate the potential stress EIPH may impose.