Respiratory control in diffuse interstitial lung disease and diseases of the pulmonary vasculature

Diffuse interstitial lung diseases are common in pulmonary practice and their etiologies encompass a diverse group of causative mechanisms. Because these diseases have clinical, physiologic and morphologic similarities, it is convenient to discuss them as a group. The authors include in this category diseases which affect primarily the pulmonary parenchyma while sparing the airways. This typically results in reduced lung volume, reduced lung, distensibility, characteristic abnormalities in metabolic gas exchange, and a characteristic symptom complex. Rather than experience a compromise of ventilation, such patients increase their ventilatory work and dyspnea becomes a prominent and early symptom. Moreover, because respiratory drive is not reduced to allow lower and more comfortable levels of ventilation, the symptom of dyspnea is in part brought about by this increased ventilation at rest and at all levels of exercise. Thus, in this group of diseases, the study of ventilatory drive and responsiveness is not merely of academic interest but is important to the understanding of the pathophysiology of this form of pulmonary dysfunction. In this discussion the authors present the results of clinical and animal studies on the regulation of breathing in diffuse interstitial lung diseases. As part of this discussion, the authors consider also the regulation of breathing in pulmonary vascular disease which involves many of the mechanisms which exist in interstitial pulmonary diseases.