DYNAMICS OF PULMONARY CIRCULATION 



1729 



fig. 49. Dye-dilution curve inscribed 

 by densitometer from peripheral artery 

 following injection of Evan's blue dye 

 (T-1824) into the pulmonary artery. 

 The upper curve is normal. The short 

 appearance time and abnormal initial 

 deflection of the lower curve are charac- 

 teristic of pulmonary arteriovenous 

 shunts. 



cause of cor pulmonale, i.e., chronic bronchitis and 

 emphysema, a combination of anatomic changes, 

 hypoxia and acidosis are involved : destruction of 

 alveolar capillaries sets the stage by restricting the 

 pulmonary vascular bed, generally without evoking 

 pulmonary hypertension; the picture is completed by 

 disturbances of alveolar ventilation and perfusion — 

 usually incidental to an acute bronchitis — which 

 superimpose the vasoconstriction of hypoxia and 

 respiratory acidosis on the structural changes (fig. 48) 

 (34')- 



It is clinically and physiologically important to 

 recognize the occurrence of right heart failure in 

 patients with cor pulmonale. Prior to heart failure, 

 the enlarged right ventricle functions normally: it is 

 filled by an atrial inflow pressure of a few mm Hg, it 



empties approximately half of its volume during each 

 ejection and it increases its output during exercise in 

 accord with metabolic requirements. The first signs 

 of right ventricular failure generally appear during 

 exercise: as ventricular emptying is compromised, 

 the mean filling pressure increases to abnormal levels 

 (7-10 mm Hg) and the increase in cardiac output is 

 no longer commensurate with the increase in oxygen 

 uptake (341 ). 



Pulmonary Edema 



In 1878, Welch produced pulmonary edema in 

 rabbits by either ligating the aorta or compressing 

 the left ventricle. He attributed the pulmonary edema 

 to the pulmonary congestion and pulmonary venous 



BEFORE VALVULOTOMY 



AFTER VALVULOTOMY 



NK 



to M M U U M A 



MM 



Hg 



-18O 



40 



J 



vL^UUUUUUUuU^ 



fig. 50. Blood pressures recorded during open thoracotomy in a patient with pulmonic stenosis. 

 Before valvulotomy. Marked right ventricular hypertension coexists with systemic hypotension. The 

 pulmonary arterial pressure pulse is vibratory. After valvulotomy. The right ventricular pulmonary 

 hypertension has been considerably relieved. The pulmonary arterial pressure has increased and the 

 pressure pulse is characteristic of pulmonic insufficiency. [After Himmelstein, el al. (210).] 



