Introduction Silicosis belongs to the interstitial lung diseases, a heterogeneous group of many diseases of a different aetiology. Common symptom of all these diseases is dyspnoea. Lung function tests usually show restrictive defect with decreased diffusion capacity (DLCO). However, the heterogeneity of these diseases brings a question, if silicosis, a typically occupational disease, differs from other non-occupational interstitial diseases in the pathogenesis of symptoms and lung function impairment. The aim of study was comparison of lung functions in patients with silicosis and non-occupational interstitial lung diseases.

Methods In total, 30 patients with simple silicosis, 32 patients with complicated silicosis and 30 patients with non-occupational interstitial lung diseases underwent spirometry, bodypletysmography and DLCO examination. We compared vital capacity (VC), forced expiratory volume in one second (FEV₁), FEV1/VC ratio (Tiffeneau index), total lung capacity (TLC), residual volume (RV) and DLCO between these 3 groups of patients.

Results Vital capacity was more decreased in silicosis, both simple and complicated compared to the non-occupational interstitial lung diseases (p<0.001). However, TLC was the highest in complicated silicosis because of high residual volume which did not change significantly in non-occupational interstitial lung diseases (p<0.001). In the group of patients with silicosis, the decrease of airflows has been shown. The highest decrease of DLCO occurred in patients with non-occupational interstitial lung diseases (63%) in comparison to simple (p<0.001) and complicated (p<0.01) silicosis. Only 10% of patients with non-occupational interstitial lung diseases had normal DLCO compared to 75% in simple silicosis and 45% in complicated silicosis.

Discussion Study confirmed differences in the pathogenesis of symptoms in silicosis and patients with non-occupational interstitial lung diseases. Apparently, in the case of simple silicosis, the symptoms are the result of bronchial obstruction without severe lung parenchyma destruction. In the case of non-occupational interstitial lung diseases, a predominant sing was decreased DLCO as a result of alveolocapillary membrane impairment without significant changes in lung volumes and airflows. However, complicated silicosis was characterised by significant volumes and airflows impairment and lung hyperinflation with decreasing DLCO.