Oscillation mechanics of the respiratory system in never-smoking patients with silicosis: pathophysiological study and evaluation of diagnostic accuracy

OBJECTIVES Silicosis is a chronic and incurable occupational disease that can progress even after the cessation of exposure. Recent studies suggest that the forced oscillation technique may help to clarify the changes in lung mechanics resulting from silicosis as well as the detection of these changes. We investigated the effects of airway obstruction in silicosis on respiratory impedance and evaluated the diagnostic efficacy of the forced oscillation technique in these patients. METHODS Spirometry was used to classify the airway obstruction, which resulted in four subject categories: controls (n=21), patients with a normal exam (n=12), patients with mild obstruction (n=22), and patients with moderate-to-severe obstruction (n=12). Resistive data were interpreted using the zero-intercept resistance (R0), the resistance at 4 Hz (Rrs4), and the mean resistance. We also analyzed the mean reactance (Xm) and the dynamic compliance. The total mechanical load was evaluated using the absolute value of the respiratory impedance (Z4Hz). The diagnostic potential was evaluated by investigating the area under the receiver operating characteristic curve. ClinicalTrials.gov: NCT01725971. RESULTS We observed significant (p<0.0002) increases in R0, Rrs4, Rm, and Z4Hz and significant reductions in Crs,dyn (p<0.0002) and Xm (p<0.0001). R0, Rrs4, Rm, and Z4Hz performed adequately in the diagnosis of mild obstruction (area under the curve>0.80) and highly accurately in the detection of moderate-to-severe obstruction (area under the curve>0.90). CONCLUSIONS The forced oscillation technique may contribute to the study of the pathophysiology of silicosis and may improve the treatment offered to these patients, thus representing an alternative and/or complementary tool for evaluating respiratory mechanics.