Abstract
A study has been made of arterial blood changes during the respiratory cycle in patients with cardiac enlargement, prolonged circulation time, and Cheyne-Stokes breathing. In these patients, Cheyne-Stokes breathing appeared to depend upon the delay in passage of blood from the lungs to the arterial chemoreceptors and respiratory center. This delayallowed cyclic over- and underventilation. There was little or no central nervous system depression. In contrast, one case of Biot's breathing is presented as an example of another mechanism responsible for periodic breathing. Here irregular breathing seems to depend on fluctuations in activity of a severely damaged central nervous system.