Histamine inhalation provocation test: method to identify nonspecific airway reactivity in equids.

The research investigates the use of histamine inhalation to diagnose non-specific airway reactivity in equine animals. The method involves analyzing changes in dynamic compliance and other respiratory measures following the inhalation of increased concentrations of histamine solutions.

Methodology

• The study used histamine solutions as a provocative agent to test changes in dynamic airway reactivity in equids (horses, donkeys, zebras, and related animals).
• The researchers measure several parameters including dynamic compliance (Cdyn), airway resistance, work of breathing, and maximum intrathoracic differences in pressure.
• Both Cdyn and airway resistance increased after the inhalation of histamine solutions.
• The change in Cdyn closely correlated with the inhaled histamine concentrations, allowing researchers to assess airway reactivity.

Results

• The research involved a histamine inhalation provocation test carried out on 40 equids.
• Using linear regression, specific histamine concentrations were calculated which resulted in a 35% decrease in dynamic compliance. These concentrations were defined as 35% provoking concentration Cdyn.
• Nonspecific airway hyperreactivity, an exaggerated airflow obstruction response, was not observed in animals that did not present clinical signs of respiratory tract disease. However, it was observed in a quarter of the equids with low-grade lung disease.
• Equids with severe lung disease demonstrated this hyperreactivity in all instances.

Conclusion

• The study suggests that the histamine inhalation provocation test is a useful method for identifying non-specific airway reactivity in equids.
• This research aids in understanding how airway reactivity can be influenced and measured using histamines, providing a potential method for early diagnosis and management of lung diseases in equids.