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.

The 30th scientific meeting of the International Society on Oxygen Transport to Tissue (ISOTT) was held at the Western Conference Centre, UMIST, Manchester, in August 2002. It was attended by some 96 delegates and accompanying persons and there were 128 presentations.

The aim of this treatise is to summarize the current understanding of the mechanisms for blood flow control to skeletal muscle under resting conditions, how perfusion is elevated (exercise hyperemia) to meet the increased demand for oxygen and other substrates during exercise, mechanisms underlying the beneficial effects of regular physical activity on cardiovascular health, the regulation of transcapillary fluid filtration and protein flux across the microvascular exchange vessels, and the role of changes in the skeletal muscle circulation in pathologic states. Skeletal muscle is unique among organs in that its blood flow can change over a remarkably large range. Compared to blood flow at rest, muscle blood flow can increase by more than 20-fold on average during intense exercise, while perfusion of certain individual white muscles or portions of those muscles can increase by as much as 80-fold. This is compared to maximal increases of 4- to 6-fold in the coronary circulation during exercise. These increases in muscle perfusion are required to meet the enormous demands for oxygen and nutrients by the active muscles. Because of its large mass and the fact that skeletal muscles receive 25% of the cardiac output at rest, sympathetically mediated vasoconstriction in vessels supplying this tissue allows central hemodynamic variables (e.g., blood pressure) to be spared during stresses such as hypovolemic shock. Sympathetic vasoconstriction in skeletal muscle in such pathologic conditions also effectively shunts blood flow away from muscles to tissues that are more sensitive to reductions in their blood supply that might otherwise occur. Again, because of its large mass and percentage of cardiac output directed to skeletal muscle, alterations in blood vessel structure and function with chronic disease (e.g., hypertension) contribute significantly to the pathology of such disorders. Alterations in skeletal muscle vascular resistance and/or in the exchange properties of this vascular bed also modify transcapillary fluid filtration and solute movement across the microvascular barrier to influence muscle function and contribute to disease pathology. Finally, it is clear that exercise training induces an adaptive transformation to a protected phenotype in the vasculature supplying skeletal muscle and other tissues to promote overall cardiovascular health. Table of Contents: Introduction / Anatomy of Skeletal Muscle and Its Vascular Supply / Regulation of Vascular Tone in Skeletal Muscle / Exercise Hyperemia and Regulation of Tissue Oxygenation During Muscular Activity / Microvascular Fluid and Solute Exchange in Skeletal Muscle / Skeletal Muscle Circulation in Aging and Disease States: Protective Effects of Exercise / References

This multidisciplinary book covers all aspects of oxygen delivery to tissue, including blood flow and its regulation as well as oxygen metabolism as discussed at the 33rd Annual Meeting of the International Society on Oxygen Transport to Tissue (ISOTT) held in Australia in 2005. Special attention is paid to methods of oxygen measurement in living tissue and the application of these technologies to understanding the physiological and biochemical basis for pathology related to tissue oxygenation.

Since there are many different tissues and organs in the body, a study of oxygen transport to tissue necessarily involves a great diversity of bodily functions. Furthermore, these tissue functions can be approached from the viewpoint of several disciplines. Even tually, however, all of these approaches must be combined to arrive at a comprehensive picture. This multidisciplinary effort, though imperative, has been implemented slowly because traditional biologi cal science has been largely organ- or discipline oriented. Initia tives to realize an effective international multidisciplinary collab oration have assumed increasing momentum for the past 20 years. These include meetings held in Bad Oeynhausen in 1965 (book in 1968, edited by D. W. Lubbers, U. C. Luft, G. Thews and E. Witzleb), in Nijmegen in 1968 (book in 1969, edited by F. Kreuzer), in Vancouver in 1970 (J. Strauss), and in Dortmund in 1971; this last was in connection with the 25th International Physiological Congress in Munich (book in 1973, edited by M. Kessler, D. F. Bruley, L. C. Clark, Jr. , D. W. Lubbers, I. A. Silver and J. Strauss). This increasing international cooperation called for a more formal organization of these individual initiatives. The credit for taking this decisive step goes to H. I. Bicher and D. F. Bruley from the U. S. A. and D. W. Lubbers and M. Kessler from Germany, who got together in 1972 to plan a large-scale inter national meeting and to organize an international society.

Since its inception in 1973, The International Society on Oxygen Transport to Tissue (ISOTT) has provided a unique forum to facilitate and encourage scientific interaction and debate. Welcoming scientists and clinicians from a broad spectrum of disciplines, each with their own particular skills and expertise, ISOTT unites them under the common theme of oxygen transport. The successful blend of scientific presentations and informal discussion which characterizes ISOTT is epitomized best by the many fundamental discoveries and technical advancements which it has spawned. The breadth and strengths of The Society's scientific base promotes the rapid progression of ideas from theoretical concepts to rigorous scientific testing and often, ultimately to the clinical arena. Each publication of the ISOTT proceedings has been recognized by Science Citation Index listing and the papers frequently establish scientific precedents and become considered as standard works in their respective fields. The 21st ISOTT Meeting was held in San Diego from August 14th through August 18th, 1993. The San Diego Meeting attracted about 150 registrants and 40 accompanying persons. Ten state-of-the-art lectures were presented by international experts in ~ transport and there were in addition two symposia -one dealing with assessment of tissue hypoxia and the other with functional heterogeneity in different organ systems. There were 100 free communications, consisting of posters accompanied by an abbreviated oral summary. All manuscripts were reviewed by the Editors for form and content, but as is customary for the ISOTT proceedings, rigorous scientific peer review was not undertaken.

The International Society on Oxygen Transport to Tissue (ISOTT) was founded in 1973 "to facilitate the exchange of scientific information among those interested in any aspect of the transport and/or utilization of oxygen in tissues". Its members span virtually all disciplines, ex tending from various branches of clinical medicine such as anesthesiology, ophthalmology and surgery through the basic medical sciences of physiology and biochemistry to the physical sciences and engineering. The fifteenth annual meeting of ISOTT was held in 1987 for three days, from July 22 to 24, at Hokkaido University in Sapporo, Japan. Previously, all ISOTT meetings had been held in Europe or the USA alternatively. This time, however, the meeting was held for the first time in an Asian country. When we first started preparing for this meeting some of our members were afraid that the number of those attending would not exceed '30. Fortunately the results were quite different. We had more than 60 participants from abroad and an even greater number from Japan. In addition to three special lectures and two symposia there were a total of 88 posters presented over the three days of the meeting. These covered all aspects of physiological oxygen transport including convection, diffusion, chemical reaction, and control of oxygen demand in blood and various tissues as well as the methods, models and instrumentation for their study. The 92 papers which comprise this volume encompass all of these areas.