Respiratory mechanics in Standardbred horses with sub-clinical inflammatory airway disease and poor athletic performance.

The study focused on examining how inflammatory airway disease (IAD) in Standardbred horses affects their respiratory function and athletic performance.

Objective and Study Groups

• The researchers’ goal was to understand and quantify respiratory mechanical dysfunctions in Standardbred horses showing poor performance and signs of Inflammatory Airway Disease (IAD) from their bronchoalveolar lavage fluid cytology.
• There were two study groups, one made up of healthy Standardbred horses and the other comprised of horses that displayed both poor performance and IAD symptoms.

Methodology

• The horses’ respiratory mechanics and breathing patterns were observed both at rest and during a state of hyperventilation, with the latter being induced artificially using a rebreathing method.

Findings

• When the horses were at rest, their respiratory mechanics and breathing patterns were similar across both groups.
• During the rebreathing period, horses with IAD had increased ventilation, accompanied by larger tidal volumes (volume of air displaced between normal inhalation and exhalation) and lower respiratory frequencies.
• These horses demonstrated frequency-dependent dynamic lung compliance during hyperventilation, which is a measure of the lung’s ability to stretch and expand.
• Above that, horses with IAD had greater viscous lung resistance, which is the frictional resistance to the airflow, and they had a higher rate of dynamic work of breathing, which equates to the amount of effort exerted by their respiratory muscles.

Implications

• The changes in pulmonary mechanics due to IAD increase the ventilatory load. This could lead to horses needing significantly more energy for their breathing, which could limit their athletic performance substantially.
• The use of rebreathing method in this study was proven effective in the early detection of respiratory mechanical dysfunction in horses with sub-clinical IAD and poor performance.