Studies on the physiopathology of chronic obstructive pulmonary disease in the horse. VII. Percentage venous admixture.

The abstract discusses a study where the researchers investigated the venous admixture (the mixing of oxygenated and deoxygenated blood) in horses with chronic obstructive pulmonary disease (COPD), and compared it with that of healthy horses. They found that horses with COPD showed a significantly larger venous admixture, indicating a higher degree of under-ventilation in their lungs.

Objective

• The primary goal of the study was to calculate and compare the percentage of venous admixture in 21 clinically normal horses and ponies and in 13 horses and ponies suffering from chronic obstructive pulmonary disease (COPD).

Methodology

• To achieve this, the researchers used blood and respiratory gas values to calculate the oxygen contents of end-capillary blood (the part of the capillary where oxygen exchange happens), arterial blood and mixed venous blood. These values were then input into a shunt equation.

Findings

• The results showed that the mean percentage venous admixture (a measure of the mixing of oxygenated and deoxygenated blood) in subjects with COPD were significantly higher than in normal subjects.

Conclusion

• The higher venous admixture in COPD horses indicated a larger proportion of their lung’s alveoli (tiny air sacs in the lungs where gas exchange occurs) were under-ventilated compared to healthy horses. Under-ventilated alveoli does not take in enough oxygen and expel enough carbon dioxide, leading to problems like shortness of breath, typical of COPD.