PHYSIOLOGY OF AORTA AND MAJOR ARTERIES 



83! 



the stroke volume derived from the dye injection or 

 Fick's procedure was within 12 per cent (44). Further 

 work brought to light two areas of discrepancies. 

 First, the predictions tended to underestimate the 

 actual stroke volumes at high pressure ranges. The 

 volume-pressure values were then empirically adjusted 

 to take care of this (94). The correction used is 

 almost identical to the difference between the single 

 continuous stretch curve of figure 3 and the curve 

 connecting the midpoints of the consecutive loops, 

 which fact suggests that there may be a theoretical 

 foundation for the empirical correction. The second 

 and more serious failure of the method is that it 

 yields a definite overestimation of the actual stroke 

 volume in some shock states in which the pressure 

 shows a brisk anacrotic rise with a high shoulder, 

 but is then poorly sustained later in systole. This 

 type of pulse has been described above. The possible 

 causes of the failure in prediction for these rare 

 pulses were discussed rather fully in a symposium 

 presented in 1952 (86a) and little more light has 

 been shed on the problem since. 



A modification of our method to make it applicable 

 to the human has been presented (19, 130). Omitted 

 from the description here are the attempts to equate 

 the stroke index with the pulse pressure. Most es- 

 pecially when the pulse pressure is taken from the 

 brachial artery, such a prediction can be relatively 

 gross (95). 



In summary, the search for an understanding of 

 the nature and functions of the distensible vessels 

 through which blood passes on its way from the heart 

 to the periphery of the circulation is a fascinating 

 pursuit. The physical basis of wave propagation and 

 of the changes in pulse form, attending such propaga- 

 tion, remain indefinite. Some of the possible factors 

 which may contribute to such contour changes have 

 been described. It remains clear that we are in no 

 position to predict a stroke volume from the form or 

 pressure values of a peripheral pulse. The form of the 

 pulse in the upper aorta, however, can reveal much 

 about cardiodynamics. It can also be used for the 

 only practical, if indirect, technique yet developed 

 for reasonably accurate stroke-by-stroke quantitation 

 of the cardiac output. 



REFERENCES 



1. Alexander, R. S. Transformation of the arterial pulse 

 between the aortic arch and the femoral artery. Am. J. 

 Physiol. 158: 287, 1949. 



2. Alexander, R. S. Arterial pulse dynamics in aortic insuf- 

 ficiency. Am. J. Physiol. 158: 294, 1949. 



3. Alexander, R. S. Factors determining the contour of 

 pressure pulses recorded from the aorta. Federation Proc. 1 1 : 



73 8 > '952- 



4. Alexander, R. S. The genesis of the aortic standing wave. 

 Circulation Research I : 145, 1953. 



5. Alexander, R. S. Influence of constrictor drugs on the 

 distensibility of the splanchnic venous system, analyzed on 

 the basis of an aortic model. Circulation Research 2: 140, 



'954- 



6. Alexander, R. S. Elasticity of muscular organs. In : 

 Tissue Elasticity. Washington, DC. : Am. Physiol. Soc, 

 1957, p. in. 



7. Alexander, R. S. Standing wave components in arterial 

 pulses of hypothermic dogs. Circulation Research 6: 580, 

 1958. 



8. Alexander, R. S., and E. A. Webb. An analysis of 

 changes in contour of the femoral arterial pulse in hemor- 

 rhagic shock. Am. J. Physiol. 150: 272, 1947. 



9. Bayliss, L. E. Rheology of blood and lymph. In: Deforma- 

 tion and Flow in Biological Systems. Amsterdam : North-Hol- 

 land Publ., 1952 



10. Bazett, H. C, F. S. Cotton, L. B. LaPlace, and J. C. 

 Scott. The calculation of cardiac output and effective 

 peripheral resistance from blood pressure measurements 

 with an appendix on the size of the aorta in man. Am. J. 

 Physiol. 113:312, 1935. 



1 1. Benninghoff, H. Uber der Beziehungen zwischen elasti- 



schen Geriist und glatter Muskulatur in der Arterienwand 

 und ihre funktionelle Bedeutung. Z. Zellforsch. mikroskop. 

 Anat. 6:349, 1927. 



12. Bleichert, A., R. Lazgus, and F. Martini. Uber die 

 Lange der stehenden Wellen in der Armarterie des 

 Menschen. Z. Biol. 105: 141, 1952. 



13. Bozler, E. Extensibility of contractile elements. In: 

 Tissue Elasticity. Washington, DC. : Am. Physiol. Soc, 

 1957. P- "02. 



14. Bramwell, J. C. Change in form of pulse wave in course 

 of transmission. Heart 12: 23, 1925. 



15. Bramwell, J. C, and A. V. Hill. The velocity of the 

 pulse wave in man. Proc. Roy. Soc, London, B, 93 : 298, 1922. 



16. Brewer, G., W. F. Hamilton, and I. Brotman. Pressure 

 pulse contours in the pulse propagated through the aorta. 

 Am. J. Physiol. 1 07 : 436, 1 934. 



1 7. Broemser, P. Uber die Grundschwingung des arteriellen 

 Pulses. Z. Biol. 100:88, 1940. 



18. Broemser, P., and O. F. Ranke. Uber die Messung des 

 Schlagvolumens des Herzens auf unblutigem Weg. Z. Biol. 



9 0: 467. '93°- 



1 9. Brotmacher, L. Evaluation of derivation of cardiac out- 

 put from blood pressure measurement. Circulation Re- 

 search $: 589, 1957. 



20. Bull, H. B. Protein structure and elasticity. In : Tissue 

 Elasticity. Washington, DC. : Am. Physiol. Soc, 1957, p. 33. 



21. Burton, A. C. Relation of structure to function of the 

 tissues of the wall of blood vessels. Physiol. Rev. 34: 619, 



'954- 



22. Cope, F. W. Elastic characteristics of isolated segments of 

 human aortas under dynamic conditions. J. Appl. Physiol. 

 "4-55. [ 959- 



