Airway obstruction in interstitial lung disease.

There is no question that most interstitial lung diseases result in structural alteration of the small airways as well as the alveoli. These structural changes of the airways produce airflow abnormalities that, depending on their extent and severity, are reflected in a variety of tests of pulmonary function. However, in most situations, obstructive lung disease rarely dominates the clinical picture. Airflow limitation may be the predominant defect in patients with Wegener's granulomatosis, lymphangioleiomyomatosis, and chronic eosinophilic pneumonia. Concomitant risk factors such as cigarette smoking or dust inhalation may contribute to airway obstruction. Sporadic cases of interstitial lung disease progressing to overt airflow obstruction have been reported. The clinical significance of airway narrowing in interstitial lung disease is a maldistribution of ventilation that causes abnormalities on gas exchange, thereby increasing the work of breathing and possibly the sensation of dyspnea.