Rethinking Chronic Obstructive Pulmonary Disease. Chronic Pulmonary Insufficiency and Combined Cardiopulmonary Insufficiency.

Almost 70 years ago, Drs. Baldwin, Cournand, and Richards defined chronic pulmonary insufficiency by the presence of respiratory symptoms, radiologic evidence of pulmonary emphysema on chest radiography, and physiologic gas trapping. A decade later, airflow obstruction on spirometry was added to the definition and insufficiency became a disease. Contemporary studies are reviving the diagnostic approach described by these early luminaries, with researchers finding that symptomatic smokers with preserved spirometry have increased exacerbations and that smokers and non-smokers with normal spirometry but emphysema on chest computed tomography have increased mortality. Hence, the Baldwin-Cournand-Richards concept of disease defined by respiratory symptoms, radiologic findings, and physiology-regardless of spirometric criteria-is being rediscovered. Baldwin, Cournand, and Richards also stated that "functionally, it is obvious that the pulmonary and circulatory apparatus are one unit," and they defined combined cardiopulmonary insufficiency as chronic pulmonary insufficiency with (left or right) cardiac and pulmonary artery enlargement. They appreciated the complexity of these interactions, which include the potential role of gas trapping in heart failure with reduced ejection fraction; the impact of emphysema on blood flow in heart failure with preserved ejection fraction; multiple contributions to cor pulmonale with increased pulmonary artery pressure; and cor pulmonale parvus in emphysema; all of which may be amenable to specific therapeutic interventions. Given the complexity of heart-lung interactions originally identified by Baldwin, Cournand, and Richards and the potentially large therapeutic opportunities, large-scale studies are still warranted to find specific therapies for subphenotypes of combined cardiopulmonary insufficiency.