Chronic emphysema of the lungs, particularly if associated with cardiac complications, has long posed a therapeutic problem. Treatment, until recently, has been limited to the supportive measures of bronchodilators, expectorants, antibiotics, oxygen, and the conventional management of cor pulmonale. The primary problems of defective alveolar ventilation, increased carbon dioxide content of the blood, and respiratory acidosis have remained unsolved.
One of the outstanding features of advanced emphysema of the lungs, particularly when it is complicated by congestive heart failure, is respiratory acidosis. This results from retention of carbon dioxide in the alveoli, consequent decrease in the alveolar blood diffusion gradient, and an increased carbon dioxide content of the blood. The ratio of carbonic acid to sodium bicarbonate, which determines the blood pH, is altered, and a reduction of blood pH ensues. In order to restore the normal carbonic acid-sodium bicarbonate ratio, the plasma bicarbonate level must be increased. This is