THE INFLUENCE OF HYPERPNEA AND OF VARIATIONS IN THE O2 AND CO2 TENSION IN THE INSPIRED AIR UPON NYSTAGMUS

Abstract

In studies on the effect of CO2 excess, O2 lack and hyperpnea on nystagmus in the human, it was found that breathing CO2 air-mixtures results in a decrease in the no. of nystagmic movements and that hyperpnea produces an increase. The brain stem reacts to increases and decreases in the CO2 tension of the blood with the same direction of change in excitability as occurs with spinal reflexes. O2 lack produces an effect on the nystagmus (decrease in no.) only under the conditions of severe anoxemia. The effects are temporary, and as soon as 3 min. afterward control values are obtained. These reactions are strikingly different from those observed in the case of the more strictly cortical processes reported in preceding papers. The differences appear to be largely associated with the relative sensitivity to O2 lack. The cortical nuerones are extremely sensitive to alterations in O supply, while the brain stem centers studied, either because of a more adequate blood supply, or for other reasons, are relatively insensitive to such changes.