Control of breathing in experimental anemia

Pulmonary ventilation was measured by a plethysmographic technique in unanesthetized, unrestrained rats and cats before and several days after they were made anemic or underwent a sham procedure. Animals were tested while breathing air, pure O 2, 10% O 2 in N 2, 7% CO 2 in air, and a mixture of 11% O 2 and 6% CO 2 in N 2. Baseline observations showed that ventilation on pure O 2 was no different from that on air, whereas hypoxia, hypercapnia and asphyxia evoked brisk ventilatory responses in all animals. Anemia did not influence ventilation during exposure to air or any of the other gas mixtures. Resting O 2 consumption was also found to be unaltered by anemia, as was the pH of arterial blood, evaluated by an in vitro equilibration method. Although the anemic state is associated with several processes that might be expected to affect the chemical control of breathing, the results of these experiments in resting, unanesthetized animals were all negative.