Oral nitroglycerin paste did not lower pulmonary capillary pressure during treadmill exercise

Area of Science:

• Equine physiology
• Cardiovascular research
• Pharmacology

Background:

• Exercise-induced pulmonary hypertension (EIPH) is a concern in equine athletes.
• Pulmonary vasodilation is a potential mechanism to mitigate EIPH.
• Nitroglycerin is a vasodilator with potential therapeutic applications.

Purpose of the Study:

• To investigate the effect of oral nitroglycerin on pulmonary vascular pressures in horses during strenuous exercise.
• To determine if nitroglycerin can prevent exercise-induced pulmonary hypertension and reduce pulmonary capillary pressure.

Main Methods:

• Six horses underwent a standardized exercise protocol at varying intensities (75%, 90%, 100% HRmax).
• Horses were treated with either 22.5 mg oral nitroglycerin or a placebo in a randomized crossover design.
• Pulmonary artery, oesophageal, and pulmonary capillary pressures were measured using a pulmonary artery catheter and dynamic occlusion technique.

Main Results:

• Resting pulmonary artery pressure significantly decreased after nitroglycerin administration (P < 0.05).
• No significant differences were observed in pulmonary capillary pressure, pulmonary wedge pressure, heart rate, or arterial blood gas tensions at any exercise intensity.
• Nitroglycerin did not attenuate exercise-induced pulmonary hypertension.

Conclusions:

• The tested dose of oral nitroglycerin (22.5 mg) does not significantly alter pulmonary vascular pressures during strenuous exercise in horses.
• This dose of nitroglycerin does not appear to protect the pulmonary vascular bed from exercise-induced hypertension.
• These findings do not support the use of 22.5 mg oral nitroglycerin for preventing EIPH in horses.