Studies on the physiopathology of chronic obstructive pulmonary disease in the horse. IV. Blood gas and acid-base values at rest.

Radiometer Blood Micro-system 2 was used in studies designed to, (a) compare the mean blood gas and acid-base values of 38 normal horses and 20 horses with chronic obstructive pulmonary disease (COPD), (b) determine the means and standard deviations of blood gas and acid-base values of Thoroughbred horses in training, and (c) investigate the relationships between clinical data, blood gas values, intracardiac and pulmonary arterial pressures in subjects with COPD. There were significant differences between the mean values for partial pressure of arterial oxygen (PaO2), arterial carbon dioxide (PaCO2) and mixed venous carbon dioxide (PvCO2) in normal and COPD subjects. The mean values and standard deviations for determinations of blood gases and acid-base status in Thoroughbred horses in training were as follows: PaO2 = 77,4 +/- 4,3 mm Hg; PvO2 (mixed venous oxygen partial pressure) = 36,2 +/- 4,1 mm Hg; PaCO2 = 40,9 +/- 5,8 mm Hg; PvCO2 = 49,4 +/- 5,0 mm Hg; pHa (arterial) = 7,358 +/- 0,051; pHv (venous) = 7,343 +/- 0,027; standard bicarbonate = 22,7 mM/l. The PaO2, the PaCO2 and the arterial pH were significantly correlated to the respiratory frequency in COPD subjects. The correlations of pulmonary diastolic pressure to both PaO2 and pHa were of probable significance (P less than 0,05) in COPD subjects. PaCO2 was highly significantly correlated to PaO2 and pHa in COPD subjects.