Respiratory muscle perfusion in ponies during prolonged submaximal exercise in thermoneutral environment.

This study focuses on understanding how blood flow changes among different respiratory muscles in ponies during a period of 30-minutes of submaximal exercise in a thermoneutral environment. The research found that the blood flow significantly increased with exercise in all respiratory muscles and that there was variability in blood flow among different respiratory muscles.

Methodology

• Eight healthy ponies were involved in the study during which the distribution of blood flow among various respiratory muscles was examined.
• The method used for this examination involved injection of radionuclide labeled 15-microns diameter microspheres into the left ventricle of the ponies’ hearts.
• The ponies were subjected to submaximal exercise for a duration of 30 minutes in a thermoneutral environment.

Results

• The heart rates and pulmonary arterial blood temperatures of the ponies increased significantly at 5 minutes, 15 minutes, and 26 minutes during the exercise. Additionally, profuse sweating was observed in the ponies.
• Similarly, mean aortic pressure increased progressively as the duration of exercise increased.
• Among inspiratory muscles (which facilitate inhalation), the greatest perfusion occurred in the diaphragm and ventral serratus, when compared with external intercostal, dorsal serratus, and scalenus muscles.
• Among expiratory muscles (those involved in exhalation), the greatest blood flow was seen in the internal abdominal oblique muscle, followed by flow in the internal intercostal and transverse thoracic muscles.
• Blood flow for all the respiratory muscles studied remained similar for the first 5 and 15 minutes of the exercise, however, increased blood flow was observed in multiple muscles after 26 minutes of exercise as vascular resistance decreased.

Conclusion

• The study concluded that all respiratory muscles were activated during submaximal exercise.
• Moreover, perfusion in these muscles displayed marked heterogeneity, indicating variability in blood flow among different respiratory muscles during exercise.