Graphic Analysis of Moment-to-Moment Changes in Blood Passing Through the Pulmonary Capillary, Including a Demonstration of Three Graphic Methods for Estimating the Mean Alveolar-Capillary Diffusion Gradient (Bohr Integration)

¹ From the Departments of Environmental Medicine and of Medicine, The Johns Hopkins University and Hospital, Baltimore, Maryland; and the Department of Physiology, Hebrew University— Hadassah Medical School and the Respiratory Research Laboratory, Hadassah University Hospital, Jerusalem, Israel

Changes in the speed with which equilibrium between alveolar gas and capillary blood is approached along the course of the pulmonary capillary are analyzed graphically. Inflections do not occur in the curve of blood oxygen content vs. time but may occur in the curve of blood oxygen tension vs. time. Such inflections depend on the rate of change of the alveolar-capillary tension gradient in relation to the rate of change of the slope of the oxyhemoglobin dissociation curve. Three graphic methods for estimating the mean alveolar-capillary diffusion gradient are presented.