Acid-base indicators in the venous and arterial blood of horses affected by recurrent airway obstruction (RAO)

The acid-base equilibrium is closely linked to gas exchange in the lungs, and respiratory exchange ratios are used to evaluate respiratory effectiveness and tissue oxygen levels. Acid-base indicators are determined in both arterial and venous blood samples. This study compares the usefulness of acid-base indicators of venous and arterial blood in monitoring the condition of horses with recurrent airway obstruction. Prior to treatment involving bronchodilating glucocorticoids, expectorant and mucolytic drugs, more pronounced changes were observed in venous blood (pH 7.283, pCO(2) 61.92 mmHg, pO(2) 35.541 mmHg, HCO3- 31.933 mmHg, BE 2.933 mmol/l, O(2)SAT 58.366%, ctCO(2) 38.333 mmol/l) than in arterial blood (pH 7.309, pCO(2) 53.478 mmHg, pO(2) 90.856 mmHg, HCO3- 28.50 mmHg, BE 3.133 mmol/l, O(2)SAT 93.375%, ctCO(2) 31.652 mmol/l), indicating compensated respiratory acidosis. The improvement of respiratory efficiency minimized acidosis symptoms in both venous blood (pH 7.365, pCO(2) 43.55 mmHg, pO(2) 47.80 mmHg, HCO3- 30.325 mmHg, BE 3.050 mmol/l, O(2)SAT 80.10%, ctCO(2) 29.80 mmol/l) and arterial blood (pH 7.375, pCO(2) 39.268 mmHg, pO(2) 98.476 mmHg, HCO3- 26.651 mmHg, BE 4.956 mmol/l, O(2)SAT 98.475%, ctCO(2) 28.131 mmol/l). Venous blood parameters were marked by greater deviations from mean values, both before and after treatment. Acid-base indicators determined in venous blood are indicative of respiratory disturbances, but they do not support a comprehensive evaluation of gas exchange in the lungs.