Forced expiration: a test for airflow obstruction in horses.

The research sought to establish if forced expiration could be used as a method for detecting small airway obstruction in horses. The study was conducted on healthy horses and those with chronic obstructive pulmonary disease (COPD), utilizing forced expiratory flow-volume curves and comparing these parameters with the lung mechanics of the horses pre- and post- therapy.

Objective of the Study

• The main aim of this study was to determine if inducing forced expiration in horses could accurately detect any obstructions in their airways, particularly within the small airways.

Methodology

• Forced expiratory flow-volume (FEFV) curves were utilized in this study, and the derived parameters from these were compared to data obtained from the lung mechanics of the horses during normal, spontaneous breathing.
• The study was conducted on nine healthy horses, three horses that had been subjected to a histamine challenge, and two horses suffering from COPD, both before and after a period of therapy involving prednisone.

Measurements and Results

• Among the parameters measured in the healthy horses were forced vital capacity (FVC), which was found to be an average of 41.6 liters, and forced expiratory flow (FEF) at various proportions of FVC. FEF ranged from 20.4-29.7 l/s.
• The histamine challenge caused a dose-dependent decrease in both FVC and FEF when the lung volume was low.
• Following therapy with prednisone, one of the horses with COPD exhibited improved lung function, attaining normal lung mechanics while the other experienced a decrease in FEF at 95% of FVC to 4.9 l/s.

Conclusion

• The study concluded that analysis of FEFV curves enables the detection of airway obstructions, regardless of whether these are induced or occur naturally.