Blood-gas measurements adjusted for temperature at three sites during incremental exercise in the horse.

This study investigates the differences in blood gas measurements between the rectum, mixed venous blood, gluteal muscle, and skin in Arabian horses during exercise. It is found that temperatures and blood gases changed significantly during exercise and recovery across different sites and suggested that the interpretation of muscle metabolism and gas exchanges could be improved if measurements are adjusted considering the different sites.

Context and Goal of the Research

• The research is situated within the broader context of understanding physiological changes in horses during exercise. Blood gas measurements are crucial for such an understanding as they inform us about the metabolism and gas exchanges in the body.
• One common practice in measuring blood gasses is to adjust them according to the rectal temperature, as it is easy to measure. However, the researchers hypothesized that this might not give accurate results, especially during intense physical activity, given the temperature differences in various parts of the body like the muscles and lungs.
• Therefore, the goal of the research was to evaluate and compare the measurements of blood gases from different sites, namely the rectum, venous blood, gluteal muscle, and skin, during exercise.

Methodology

• Seven Arabian horses underwent an incremental exercise test on a treadmill. Temperatures were measured in the different sites using thermocouples, a device used to measure temperature accurately.
• Blood samples were collected from the horses’ carotid artery and pulmonary artery before each increase in speed and during recovery. In these samples, the researchers measured the blood gases and pH level at a constant temperature of 37 degrees Celsius.
• All the variables were then adjusted to account for the rectal temperature, venous temperature, and muscle temperature.

Findings

• Adjusted variables at different sites during exercise and recovery were found to differ significantly from each other.
• Linear and polynomial equations were used to describe the time course of venous temperature and from the rectal and skin temperature during exercise.
• In recovery, the skin temperature was used to inform these equations.
• Based on these results, the authors argue that adjusting blood gas measurements according to muscle temperature or venous temperature, rather than rectal temperature, might provide a better understanding of muscle metabolism and gas exchanges.
• These can be predicted from skin temperature in addition to rectal temperature during strenuous exercise, and from skin temperature during recovery.