Regulation of Tissue Oxygenation, Second Edition

Roland N. Pittman is a professor of Physiology and Biophysics at the Medical College of Virginia Campus of Virginia Commonwealth University in Richmond, Virginia. He received his S.B. in Physics from the Massachusetts Institute of Technology in 1966, his M.A. in Physics from the State University of New York at Stony Brook in 1968, and his Ph.D. in Physics from the State University of New York at Stony Brook in 1971. He then received postdoctoral training in microcirculation in the laboratory of Dr. Brian R. Duling in the Department of Physiology at the University of Virginia. Dr. Pittman also holds joint faculty appointments in the Department of Biomedical Engineering and the Department of Emergency Medicine at Virginia Commonwealth University. His research has focused on the transport of oxygen and its regulation from the perspective of the microcirculation, and he has worked with several different colleagues to develop intravital microscopic methods to measure blood and tissue oxygenation. He has published more than 150 articles on oxygen transport and related topics.

This presentation describes various aspects of the regulation of tissue oxygenation, including the roles of the circulatory system, respiratory system, and blood, the carrier of oxygen within these components of the cardiorespiratory system. The respiratory system takes oxygen from the atmosphere and transports it by diffusion from the air in the alveoli to the blood flowing through the pulmonary capillaries. The cardiovascular system then moves the oxygenated blood from the heart to the microcirculation of the various organs by convection, where oxygen is released from hemoglobin in the red blood cells and moves to the parenchymal cells of each tissue by diffusion. Oxygen that has diffused into cells is then utilized in the mitochondria to produce adenosine triphosphate (ATP), the energy currency of all cells. The mitochondria are able to produce ATP until the oxygen tension or PO2 on the cell surface falls to a critical level of about 4-5 mm Hg. Thus, in order to meet the energetic needs of cells, it is important to maintain a continuous supply of oxygen to the mitochondria at or above the critical PO2 . In order to accomplish this desired outcome, the cardiorespiratory system, including the blood, must be capable of regulation to ensure survival of all tissues under a wide range of circumstances. The purpose of this presentation is to provide basic information about the operation and regulation of the cardiovascular and respiratory systems, as well as the properties of the blood and parenchymal cells, so that a fundamental understanding of the regulation of tissue oxygenation is achieved.