Blood gas measurements during exercise: errors due to temperature correction.

The research article investigates how the correction of blood gas measurements to rectal temperature could lead to errors compared to when the measurements were corrected to temperatures where gas exchange actually occurs. The study used exercising horses and steers to explore this phenomenon.

Objective of the Research

• The primary purpose of this research was to determine the accuracy of blood gas measurements corrected to rectal temperature in comparison to those corrected to the temperatures at the sites of gas exchange; the pulmonary artery and intramuscular sites. The errors resulting from these corrections were then analyzed.

Research Methodology

• Horses and steers weighing about 450 kg were used in this study. They were made to run on a treadmill at speeds that elicited their maximum oxygen consumption rate.
• Temperatures were then measured in different body departments including the rectal and pulmonary arterial areas.
• The temperature of the intramuscular area was only measured in horses.

Key Findings

• The study found that during the run, pulmonary arterial temperature increased at a faster rate than rectal temperature in both horses and steers. The difference between the two temperatures, however, was dependent on the exercise’s intensity and duration.
• Only in horses, the intramuscular temperature significantly increased quicker than the pulmonary arterial temperature during the run and it decreased more slowly after the run.
• The significant finding is that the correction of blood gas values measured at an analyzer temperature of 37 degrees Celsius to rectal temperature, without considering the transient increases of pulmonary arterial and intramuscular temperatures that did not manifest in rectal temperature readings, resulted in inaccurate estimates of blood gases.
• This inaccuracy falsely indicated that both species experienced a more severe deficiency of oxygen in the blood (hypoxemia) than actually occurred at their maximum oxygen consumption rate.
• The inaccurate measurements also concealed the presence of substantial carbon dioxide in the blood (hypercapnia) experienced by the horses at maximum oxygen consumption rate.

Conclusions and Implications

• The study hence concludes that applying correction to blood gas measurements using rectal temperature alone can lead to significant errors.
• The findings highlight the importance of considering other body temperatures such as those in the pulmonary arterial and intramuscular areas, especially during physical activity, to obtain accurate blood gas analyses.