Steady-state diffusing capacity for carbon monoxide in the rat

Abstract

Steady-state diffusing capacity for carbon monoxide was determined in rats anesthetized by pentobarbital at normoxia and hypoxia and in conscious rats at normoxia by three experimental arrangements. The carbon monoxide back pressure was estimated by a method adapted to small animals and its influence was evaluated. There was a significantly higher diffusing capacity, alveolar ventilation, and oxygen uptake in the unanesthetized rats compared with the anesthetized animals at normoxia. A linear regression between diffusing capacity and alveolar ventilation was found in all rats at normoxia. The diffusing capacity measured at hypoxia was higher than in normoxic animals of similar body weight at the same level of ventilation. No significant difference between the previously measured diffusing capacity for oxygen (Turek, Frans and Kreuzer, 1970) and the present values of the carbon monoxide diffusing capacity in rats of similar body weight was found. The relationship between the diffusing capacity for oxygen measured directly and that calculated indirectly from the diffusing capacity for carbon monoxide is discussed.