Biophysical Analyses of Blood Vessel Walls and Blood Flow

Our knowledge of hemodynamics, or the physics of blood flow, has expanded exponentially in the last 10 or IS years, so the task of providing a comprehensive review in a finite length of time is impossible, at least for me. Thus I have accepted the editor's invitation to write primarily on those aspects of the subject which intrigue me. McDonald's book, Blood Flow in Arteries (133), which appeared in 1960, began the phase of rapid growth of the field of hemodynamics. Attinger's 1964 book Pulsatile Flow in Arteries (9) summarized developments until that time. Bergel's two-volume edition Cardiovascular Fluid Dynamics (23), which appeared in 1972, updated the literature as seen by the contributors. McDonald's second edition (134) came out in 1974 (published posthumously) and provides a more comprehensive survey of the field, although with a bias toward his own work and that of his former students. The text by Strandness & Sumner (214), while designed for surgeons, provides a useful review of hemodynamics for physiologists as well. A recent NATO symposium in Houston was published late in 1976 (114) and, like Bergel's text, summarizes developments in the selected areas of interest of the contributors. While I have access to some chapters in manuscript form, others are not available. Many of the papers were of more surgical than physiological interest. A survey of the literature from 1972 to 1975 inclusive suggests that the major developments have come from better instrumentation, and more extensive use of mathematical and physical models. We still do not know precisely what determines the blood velocity at any one point in any artery. Both the elastic properties of the arterial wall and the fluid factors governing the blood flow are involved. Now we can determine incremental elastic properties of arteries and also have a better understanding of the role of vascular smooth muscle (contracted or relaxed) in