Recent advances in our understanding of the natural history of chronic airway obstruction have identified aspects of this process that may enhance the morbidity and mortality of patients with a progressive increase in airway resistance. These advances have helped us to be more specific in the investigation and quantitation of the disease in the pulmonary function laboratory and to be more precise in our therapeutic management. Experience has taught us that the most useful measurement with which to characterize the degree of disease and its rate of progression is the forced expired volume in one second (FEV1). The comprehensive studies of Dr. Charles Fletcher in London have demonstrated that the single most important therapeutic factor is avoidance of all airway irritants. The application of aggressive bronchial hygiene in patients with obstructive airways disease may produce an initial improvement in the FEV1 but will not in itself alter the rate of decline in pulmonary function. As the degree of airway obstruction increases, a number of interrelated physiologic abnormalities develop including hypoxemia, hypercarbia, polycythemia, cor pulmonale, and eventually, acute or chronic respiratory failure. These abnormalities account for most of the morbidity in this condition and the majority of patients who develop them have a high degree of airway obstruction. It is not unusual, however, to see patients with a moderate degree of airway obstruction who also manifest these problems. The purpose of this paper is: (1) to review the relationship between a progressive increase in airway obstruction and the associated physiologic abnormalities, and (2) to discuss the therapeutic interventions that show promise of reducing the morbidity from these accelerated physiologic abnormalities
