Pulmonary function measurements during repeated environmental challenge of horses with recurrent airway obstruction (heaves).

The research paper discusses the observations and experiments conducted on horses to understand the reproducibility in clinical variables, blood gas measurements, and lung functions when exposed to moldy hay, leading to a condition called heaves. Researchers investigated the changes in a set of parameters such as breathing rate, lung resistance, arterial O2 and CO2 tensions, and work of breathing before and after the challenge of exposure to moldy hay.

Methodology

• The researchers tested a set of horses with naturally acquired heaves or recurrent airway obstructions and a group of control horses that didn’t have this condition. The horses were studied before and after subjecting them to a challenge with moldy hay. This process was repeated three times to assess variations in different parameters.
• The variability of several variables was evaluated for their repeatability, including the clinical score (an overall health indicator), arterial oxygen and carbon dioxide tensions, pulmonary function variables (breathing rate, tidal volumes, flow rates), lung resistance, dynamic compliance (ability of lungs to expand and contract), and the work of breathing.

Results and Findings

• Before exposing them to moldy hay, the researchers found notable differences between the control horses and horses with heaves in parameters such as the clinical score, expiratory flow rate near the end of expiration, lung resistance, and work of breathing.
• After the moldy hay challenge, most variables in control horses remained pretty much the same. However, in horses with heaves, significant changes were observed in several parameters like clinical scores, arterial oxygen and carbon dioxide tensions, breathing rate, peak tidal inspiratory and expiratory flow rates, dynamic compliance, lung resistance, and work of breathing.
• The data analysis showed only a few statistically significant differences between repeated challenges, suggesting a high level of reproducibility and consistency in the observed effects of mouldy hay exposure.

Conclusions

• The researchers concluded that the obstruction in horses with heaves can be measured in a repeatable manner. The consistent reactions in the pulmonary functions and blood gas measurements of the afflicted horses signify the reproducibility of their physiological response to the moldy hay challenge.