Effects of atropine in ponies with recurrent airway obstruction.

The research article primarily investigates the impact of a drug named atropine on lung function and airway reactivity in two groups of ponies – those with a history of recurrent airway obstruction, and those without. It was determined that atropine was able to reduce pulmonary resistance in ponies with airway obstruction during acute attacks.

Research Design

• The research was a comparative study involving two groups of ponies. The principal group comprised ponies with a history of recurrent airway obstruction when housed in a barn and fed hay, while the control group consisted of ponies without any history of airway obstruction.
• Each principal pony was paired with a control pony for a comparison of the effects of administering atropine.
• Measurements, both before (Period A) and during an acute attack (Period B) of airway obstruction, were taken to understand the function and reactivity of the airways in both conditions.
• The effects of administrating atropine were monitored by measuring the changes in pulmonary resistance (RL), dynamic compliance (Cdyn), and aerosol histamine concentration required to decrease Cdyn to 65% of the baseline (ED65Cdyn).

Key Findings

• Atropine did not make a significant difference to pulmonary resistance, dynamic compliance, or airway responsiveness in either group of ponies during Period A. It was also observed that atropine did not affect control ponies during Period B.
• In principal ponies, during an acute attack (Period B), atropine did not alter Cdyn or ED65Cdyn. However, it effectively reduced RL and the change in RL induced by 0.1 mg/ml histamine (delta RL0.1).
• The correlation between the change in RL and delta RL0.1 suggests that the decrease in pulmonary resistance likely results from geometric changes in the airways due to atropine administration.

Implications of the Study

• The study concludes that atropine showed little impact on resting bronchomotor tone in normal ponies, but significantly reduced the increase in pulmonary resistance in ponies experiencing an acute attack of airway obstruction.
• Interestingly, the research found little to no evidence of muscarinic receptor involvement in the pony’s response to aerosol histamine – both in principal and control ponies.
• The findings of the study could contribute to improved medical treatments for horses suffering from recurrent airway obstruction, utilising atropine’s beneficial influence.