Expiratory lung crackles in patients with fibrosing alveolitis.

Inspiratory lung crackles are a diagnostic feature of interstitial pulmonary fibrosis, but expiratory crackles are not well documented. In a phonopneumographic study of 13 patients with fibrosing alveolitis, expiratory crackles were audible with the stethoscope in 12. Phonopneumographic analysis of these 12 patients showed the crackles to be fine with the initial wave deflection of the expiratory and inspiratory crackles in opposite directions. They were few in number, occurred predominantly in mid- and late expiration, and were not affected by varying the volume history or by breath holding maneuvers. These observations support the theory that some crackles are produced by vibration of the walls of peripheral airways. In addition, this group of patients showed a significant correlation between the number of expiratory crackles and the reduction in predicted transfer factor, suggesting that expiratory crackles may be a clinical indicator of the severity of disease in fibrosing alveolitis.