Cardio-pulmonary function of congested lungs.
Investigation of the cardio-pulmonary function of six patients in chronic renal failure who required regular haemodialysis showed that their lungs continued to transfer gas to the arterial blood normally even when they contained a fourfold increase in their water content, though hypoxaemia developed whenever cardiac failure supervened. At the time of study (by multiple indicator-dilution techniques using radioactive labelled albumen, sodium, and water) all of them had excess blood (Vc.) and excess water (P.E.V.W.v) in their lung capillary bed though the latter decreased after exercise in four subjects. There was a fair correlation (r = 0.9 and 0.8) between the two components of the carbon monoxide transfer factor (Vc. and Dm) and the amount of extravascular water (P.E.V.W.v). When the lungs were overloaded with fluid they actually increased their ability to transfer gas during exercise. But the gas exchange deteriorated because of ventilation/perfusion imbalance when heart failure supervened with an impaired exercise output. In all cases the minute ventilation (VE) and ventilatory equivalent (VO2/VE) for oxygen were increased at rest and during exercise. The sodium (24Na) exchange between the blood and extravascular lung tissue decreased when the blood flow through the lungs was augmented but the reverse occurred when cardiac function was poor. The arteriovenous oxygen content difference CaO2-CvO2 was less than normal at rest but reached maximal values during exercise.