The Nature of Gastric Hypersecretion of Acid in Patients with Duodenal Ulcer

during apnoea, so that anoxaemia cannot by itself be held responsible.The carbon dioxide tension is, however, at its lowest during the apnoeic phase (Harrison, 1939), and, since cerebral bloodeflow is directly related to the carbon dioxide tension of the blood (Kety and Schmidt, 1946), reduction of blood flow from this cause may be responsible.We have no data on this aspect. SummaryTwo patients with chronic Cheyne-Stokes respiration are described in some detail.These with a further three patients were investigated, using an ear oximeter.It has been shown that the highest arterial oxygen saturation occurs during the period of apnoea, the lowest during the hyperpnoeic interval.This is due to a delay in circulation time and has been demonstrated by means of dye time-concentration curves.The length of the apnoeic phase seems to be related to the prolongation of the circulation time.The effects of oxygen, carbon dioxide, and amino- phylline on this condition have been studied together with their effect on arterial saturation.In our patient with chronic Cheyne-Stokes respiration a mid-brain lesion is described.The mechanism caus- ing this form of respiration is discussed.It is suggested that two of the factors are a prolonga- tion of circulation time and a change in sensitivity of the respiratory centre.The latter may arise fr6m interruption of cortical pathways to this centre.We should like to express our thanks to Dr. Jean Taylor for the pathological reports, to Dr.