Ultrasonographic measurement of diaphragm muscle activity for assessment of respiratory function in horses.

The study investigates the use of ultrasonographic imaging as a non-invasive method for evaluating the respiratory function of horses, especially the diaphragm’s activity. It demonstrates a correlation between a horse’s weight and the thickness of its diaphragm, and suggests the use of diaphragm thickening fraction for comparisons.

Research Methodology

• The research involved 20 adult horses with an average weight of 409±50 kg, height of 1.47±0.05 m, and age of 16±6 years.
• The diaphragm’s thickness was measured at end-inspiration and end-expiration using two ultrasound modes, B-mode and M-mode.
• The ultrasound transducer was placed in the 10th, 11th and 12th intercostal spaces on both sides of the horse’s chest.

Significant Findings

• Measurements taken at end-inspiration during situations of forced vital capacity (the maximum amount of air a horse can forcibly exhale from its lungs after taking the deepest breath possible) were greater than those during normal, unforced breathing in terms of diaphragm thickness, thickening, and thickening fraction.
• Diaphragm thickness was found to be greater in horses weighing more than 400kg at the point of inspiration and at the end of expiration.
• No significant difference was found in the thickening fraction between horses weighing less than or equal to 400 kg and those weighing more than 400 kg.

Conclusions

• The study proves that ultrasonographic measurement of diaphragm thickness, thickening, and thickening fraction can effectively assess respiratory function in horses.
• Given the relationship found between horses’ weight and diaphragm thickness, it’s recommended to use the diaphragm thickening fraction as a standard for comparison between horses.
• The increased activity in the diaphragm with forced breathing implies a positive correlation between breathing workload and diaphragm contraction.