Cardiorespiratory measurements and indices of oxidative stress in exercising COPD horses.

This study investigates the effects of a chronic obstructive pulmonary disease (COPD) crisis on several physiological parameters in horses, such as heart rate, lactate levels, and measures of oxidative stress, during exercise until fatigue. It found that horses suffering from a COPD crisis show a significant decrease in performance, which is not connected with an increase in oxidative stress.

Study Methodology

• The study observed six horses suffering from COPD, and they were assessed twice – once during a COPD crisis (C), and once during a clinically stable period (R).
• The exercise routine was a progressively intense treadmill workout until the horses showed exhaustion symptoms. The performance was evaluated based on the number of steps taken and the duration of the last step in the exercise.
• Heart rate was continuously monitored, and samples of arterial and mixed venous blood were collected before, immediately after, and an hour post-exercise. These samples were analyzed for partial pressures of oxygen (O2) and carbon dioxide (CO2), plasma lactate (LA), packed cell volume (PCV), reduced glutathione, glutathione disulphide, glutathione redox ratio (GRR), and lipid hydroperoxides (LPH) as markers of oxidative stress.

Findings and Interpretations

• A COPD crisis significantly shortened the time to fatigue, meaning the horses could not maintain the exercise for as long as when they were in remission.
• Even though the intensity and duration of exercise were lesser during the crisis, the peak heart rate and plasma lactate levels were similar in both C and R stages.
• Arterial hypoxaemia and hypercapnia, along with packed cell volume, were significantly higher during the COPD crisis, indicating increased physiological stress.
• Contrary to expectations, the oxidative stress appeared to be higher during remission than during the COPD crisis, as reflected by the marked increase in GRR and LPH values one hour post-exercise.
• The absence of exercise-induced oxidative stress during the COPD crisis might be related to the lower intensity of exercise achieved and the severe hypoxaemia experienced in this condition.

Conclusion

• The study concluded that horses during a COPD crisis have notably reduced exercise performance.
• The reasons for this exercise intolerance are not yet clear but are not believed to be associated with increased oxidative stress during the crisis. More research is needed to fully understand the physiological responses of COPD horses during exercise.