Ventilatory responses of the horse to exercise: effect of gas collection systems.

The study investigates if respiratory masks interfere with normal gas exchange in horses during exercise. Different types of respiratory masks were tested to see their effect on the horses’ blood gas levels and heart rate-O2 uptake relationship.

Objective of the Research

• The objective of the research was to examine whether the use of respiratory masks on horses during strenuous exercise could impact their normal gas exchange process.

Research Design and Methodology

• Four distinct types of collection systems were examined. Two were flow-through systems and the other two incorporated one-way valve systems with subject-generated airflow.
• Six horses were subjected to a sequence of standard treadmill exercise tests, consisting of a 2-minute warm up, followed by galloping for one minute each at speeds of 8, 9, and 10 meters per second.
• The horses were tested six times with each of the four respiratory masks, cycling through different flow rates for the flow-through systems.
• During the exercise at each speed, arterial blood gas tensions were measured for each system and compared to the values that were measured when horses exercised without a mask.

Findings

• Results indicated that Hypercapnia, an excessive amount of carbon dioxide in the bloodstream, developed during exercise with all of the respiratory masks except the one with the highest flow-through system (6,300 liters per minute).
• All horses became hypoxemic (low oxygen levels in the blood) during every exercise test, however, this condition was most severe when using systems incorporating one-way valves.
• The researchers found an abnormal heart rate-O2 intake relationship when using these respiratory masks, implying that these systems might severely inhibit ventilation.

Conclusion

• The study concluded that certain respiratory masks can interfere with normal gas exchange in horses during intense exercise.
• The findings suggest that experiments conducted using respiratory systems incorporating one-way valves do not reflect the normal exercise conditions, as they significantly impede ventilation and cause abnormal blood gas levels and heart rate-O2 uptake relationships.