562 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION I 



depletion (108). Dogs in extremis from hemorrhagic or 

 traumatic hypotension do not often show discrepant 

 pulses. 



The forms of these discrepant pulses show stigmata 

 that make them recognizable on inspection. The 

 diastolic pressure is relatively high, systole is relatively 

 short, and there is often an early systolic peak fol- 

 lowed by a marked preincisural drop. Perhaps the 

 most important evidence of a discrepant pulse is the 

 slope of the diastolic limb. If the diastolic pressure is 

 above 40 mm Hg and the slope of diastole so flat that 

 its prolongation to the initial upstroke cuts the 

 anacrotic limb below one-half the pulse pressure, the 

 pulse curv'e is considered one that will give a calcu- 

 lated stroke index that is larger than that calculated 

 from other methods (108). 



A refinement of the pulse contour method was de- 

 scribed by which the time course of cardiac ejection 

 could be calculated (no, in) and compared with the 

 cardiometer curve of Wiggers & Katz (146). The 

 ejection curves were calculated according to the same 

 principle as that for calculating the stroke volume, 

 except that the uptake was figured from pressure 

 measurements made at lo-msec intervals from the be- 

 ginning of the pulse wave, and the drainage figured 

 as in the stroke volume calculation and partitioned 

 from interval to interval beginning at Tw and in 

 accordance with the early pressures (for details of 

 this calculation see 1 10 and 1 1 1). The curves plotted 

 from this measurement agree closely in contour with 

 those drawn by the cardiometer (73, 146) and show 

 the large variations in the time course of ejection 

 which cause the greatly differing pulse forms seen 

 under different circumstances (see fig. 9). 



BALLISTOC.-\RDIOGR.APHY 



As the heart pumps blood around the circulation, 

 it accelerates the blood from a static condition in the 

 ventricle to rapidly moving streams in the aorta and 

 in the pulmonary artery. The recoil from this sudden 

 acceleration tends to move the body in the opposite 

 direction, the two forces being equal and opposite. 

 As the surge of blood in the great arteries reaches the 

 arch of the aorta or the bifurcation of the pulmonary 

 artery it is stopped in its headward course, and either 

 mostly reversed down the aorta or surges laterally out 

 the pulmonary branches. The impacts at the arch 

 and pulmonary bifurcation occur during early systole, 

 and they are in opposite direction to the cardiac re- 

 coil. There arc other impacts, occurring later, but 



60- 



50 



40 



30 



20 



10 



/ • 



o 



UJ 



-> 



z 



/ 



/ 



/ 



/ 



•/ 





^ 



-^. 



^. 'STROKE VOLUME. CC . PULSE CONTOUR 



10 



20 



30 



40 



50 



60 



FIG. 7. Relation of stroke volume as calculated from the 

 Fick or dye dilution methods and that calculated from the 

 pulse contour. [From Hamilton & Remington (64).] 



they have not been used in calculating the stroke 

 volume. 



The first attempt to record the movements of the 

 body in response to these forces was that of Gordon, 

 followed by Henderson and several others (for refer- 

 ences see 59). The earliest effort to get quantitative 

 optical records of these forces was that of Starr and 

 colleagues (128). Using a complex equation contain- 

 ing terms for age, sex, as well as dimensional terms, 

 the first two strokes of the ballistocardiogram were 

 used in calculating the cardiac output. The equation 

 was admittedly an empirical one of best fit and has 

 been modified repeatedly by these and other authors 

 (e.g., 104, 105). 



There are several reasons why the relation between 

 the ballistocardiogram and the stroke volume is hard 

 to understand theoretically. In the first place the re- 

 coil is evident only to movements which work in 

 accelerating blood within the great arteries. This is 

 clear from a series of experiments on a model (25, 59) 

 in which the drixins; force was cut short in early, mid, 

 and late "systole." This dri\ing force caused ejection 

 to continue and the stroke \olume to become greater 

 the longer it lasted. As long as the dri\iiig force (sud- 

 den increase in air pressure surrounding a collapsible 

 bag which acts like a heart) was of the same intensity, 

 the recoil curve was unchanged, even though ejection 

 lasting until late "systole" would give a much larger 

 stroke \olume than ejection cut short in early systole. 



