Forced expiration: a test for airflow obstruction in horses

Area of Science:

• Equine respiratory physiology
• Pulmonary function testing

Background:

• Small airway obstruction is a significant concern in equine respiratory health.
• Accurate detection of airway obstruction is crucial for diagnosis and treatment.

Purpose of the Study:

• To evaluate the efficacy of forced expiratory flow-volume (FEFV) curve analysis in detecting small airway obstruction in horses.
• To compare FEFV parameters with lung mechanics data during spontaneous breathing.

Main Methods:

• FEFV curves were generated by inducing forced expiration in horses.
• Lung mechanics were measured during spontaneous breathing.
• Data were collected from healthy horses, horses with induced airway obstruction (histamine challenge), and horses with chronic obstructive pulmonary disease (COPD) before and after treatment.

Main Results:

• Healthy horses exhibited normal forced vital capacity (FVC) and forced expiratory flow (FEF) values.
• Histamine challenge induced a dose-dependent decrease in FVC and FEF at low lung volumes, indicating obstruction.
• COPD horses showed improved lung function after prednisone therapy, but FEF at 95% of FVC remained decreased, suggesting persistent small airway obstruction.

Conclusions:

• FEFV curve analysis is a valuable tool for detecting small airway obstruction in horses.
• The method can identify both experimentally induced and naturally occurring airway obstructions.
• FEFV parameters provide insights into small airway function that may not be apparent during tidal breathing.