8 5 6 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



A P = P, - P 2 



fig. 23. The "raking in" or "vis a fronte" action of the right 



ventricle and tricuspid valve ( diastole ; systole), and 



the principle of blood movement without net gradient. 



SURCAVA PRES. 



fig. 24 Pulsatile How in the superior vena cava [Brecher (5)] 

 as measured by the bristle flowmeter, showing the effect of 

 changes in heart rate on inflow into right atrium. Venous 

 return is phasically recorded with the bristle flowmeter in the 

 superior vena cava (open chest). From above downward the 

 tracings are time, aortic pressure in mm Hg, superior vena 

 caval flow in ml/min, and superior vena caval pressure in mm 

 HjO. PAS denotes peak of atrial systole. 



systolic pressure reversal demonstrated already across 

 the aortic valve. This difference is possibly due to two 

 causes: first, there may be more effective resistance in 

 the pulmonary artery due to the sharp turn that it 

 makes immediately after arising from the ventricle, 

 and, second and more importantly, since there is a 

 smaller acceleration and more sustained peak flow, 

 the differential term of the equation relating flow and 

 differential pressure is relatively small. This equation 

 rewritten for convenience is as follows: AP = L/ 

 dF dt + RF. 



Pulsatile Flow in the Pulmonary Capillary Bed 



Direct observations through the microscope of 

 pulmonary capillaries in vivo clearly indicate a 

 markedly pulsatile character of the blood flow. In 

 addition, nitrous oxide uptake curves in the body 

 plethysmograph which represent an integral relation- 

 ship to the pulmonary capillary flow demonstrate 

 pulsatile flow through the vessels perfusing the al- 

 veoli. These pulsations are relatively small, however, 

 and are superimposed upon a strong mean flow 

 through the same vessels. Pulmonary capillary 

 pressures, taken through the wedged cardiac catheter, 

 generally demonstrate a marked pulsatile pressure 

 in the pulmonary capillaries, and thus represent 

 indirect evidence of phasic flow in these vessels. 



VI. NONLAMINAR FLOW AND MURMURS 



Normal Murmurs 



Careful evaluation of the normal circulation for 

 murmurs by means of sensitive microphones, in- 

 cluding the application of a barium titanate phono- 

 catheter directly to the surface of the heart and 

 blood vessels, has been made. The assumption is 

 made that the presence of a murmur indicates a 

 nonlaminar and turbulent flow pattern. Frequently, 

 one can detect a brief systolic murmur in the arch of 

 the aorta corresponding in time to the peak of the 

 ejection pulse. Groom (19) has also shown con- 

 siderable indirect evidence that systolic murmurs can 

 frequently be recorded from normal humans with 

 sensitive microphones on the body surface under the 

 low-background noise conditions of a soundproof 

 room. In addition, low-frequency vibrations can be 

 recorded from the normal cardiac chambers during 

 diastole by means of intracardiac phonocatheters. 



Relationship Between the Murmur of Coarctation 

 Stenosis and Blood Flow Through the Stenotic Area 



A study of the pressure-flow-murmur dynamics in 

 coarctation of the aorta illustrates many principles 

 applicable to stenosis of the larger arteries as well as 

 flow through the pathological heart valve orifices of 

 stenosis and regurgitation. 



Coarctation was produced by progressively con- 

 stricting a wire loop passed around the descending 

 aorta of an experimental animal (49) (fig. 27). 

 Changes in the flow contour were noted during 

 constriction from a normal diameter of 6.5 mm down 



