Relationship between lung inflammation or fibrosis and frequency dependence of compliance in interstitial pulmonary diseases.

In order to find a physiological parameter which discriminates between the predominance of inflammation or fibrosis, pulmonary function tests and open lung biopsy were performed on 19 patients with interstitial lung disease. Our results showed that the only test which may be useful is the dynamic lung compliance/quasi-static lung compliance (Cdyn/Cst) index. In this context, values equal or lower than 0.85 of the Cdyn/Cst index indicate that inflammation predominates, and values higher than 0.85 suggest that interstitial fibrosis is the main feature.