Study objective: Determine why crackles on chest auscultation are characteristic of most interstitial lung diseases, but may not be heard in sarcoidosis.
Design: All patients with sarcoidosis or cryptogenic fibrosing alveolitis seen during a four-week period were studied. In a second study to relate ausculatory findings to anatomy, patients with fibrotic changes on their chest roentgenogram were studied.
Setting: Patients were recruited from outpatient clinics.
Patients: In the first part, all patients seen over the course of one month were studied. In the second study, patients with pulmonary fibrosis seen on chest roentgenograms were studied.
Interventions: For the first study, two independent observers performed auscultation on five sites for crackles and reviewed four roentgenogram quadrants for changes. For the second study, patients underwent VC measurements, auscultation, and high resolution computer tomography scans.
Measurements and results: For the first study, crackles were noted at greater than 2 sites in all 11 CFA patients, but only one of 17 SARC patients (p less than 0.001). Roentgenogram changes were seen in greater than 2 quadrants in nine of 11 CFA patients and eight of 17 SARC patients (p = ns). In the second study, the VC was similar in the two groups: SARC: 1.96 +/- .90 L (means +/- SD), 58 +/- 20.4 percent predicted; CFA: 1.81 +/- .33 L, 59 +/- 9.2 percent predicted). Only two of 14 SARC patients had crackles in greater than 1 area, while all 14 CFA patients had crackles at greater than 2 sites. The HRCT studies were read by a radiologist unaware of the diagnosis. The presence and degree (0 to 3 scale) of subpleural and peribronchial fibrosis were scored. Twelve SARC patients had peribronchial changes (mean score 1.9 +/- 1.08), while only eight had subpleural fibrosis (mean score .6 +/- .52). There was a significantly different pattern in the CFA patients, where eight had peribronchial fibrosis (mean score = .9 +/- .78, p less than 0.05) and all 14 had subpleural fibrosis (mean score = 1.6 +/- .73, p less than 0.01).
Conclusions: We conclude that crackles are more frequent in fibrosing alveolitis than in sarcoidosis; this difference may be due to the distribution of parenchymal fibrosis.