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

Abstract

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.

Early Diagnosis of Respiratory Abnormalities in Asbestos-Exposed Workers by the Forced Oscillation Technique

“…Other authors, investigating early changes in sarcoidosis, found results similar to our findings [28]. These results are also consistent with those observed in systemic sclerosis [23], silicosis [29] and smoking [77]. In subjects with coal mining-related pneumoconiosis, a pattern of reticular nodulation on the chest radiograph was reported, representing the initial stage of dust deposition in the lung.…”

Relationships between the pulmonary densitometry values obtained by CT and the forced oscillation technique parameters in patients with silicosis

“…In agreement with other studies, 21,22 patients with silicosis showed changes in both reactive and resistive properties of the respiratory system. Silicosis is characterized by airway impairment owing to its distortion and compression by the silicotic nodules and the involvement of the lung parenchyma owing to the conglomerate masses and scar-related emphysema.…”

“…Thus, the extensive replacement of the pulmonary parenchyma by fibrous tissue in patients with silicosis can contribute to changes in elasticity, which in turn can cause an imbalance in the respiratory system's time constants and increase the heterogeneity of the system. 22 In this study, a reduced dynamic compliance of the respiratory system was associated with larger size and higher weight of nonaerated compartment. Dynamic compliance of the respiratory system includes the compliances of the lung and bronchial walls, the chest wall and thoracic gas compression.…”

“…Zrs4Hz is related with the necessary work to promote the movement of air in the respiratory system and may therefore be associated with fatigue and shortness of breath, which are common symptoms in patients with silicosis. 22,43,44 We suggest that Zrs4Hz can be used as a severity marker for silicosis. Thus, Zrs4Hz might be of clinical importance in the clinical scenario.…”

“…FOT has a high potential to increase our understanding of the pathophysiology of respiratory diseases as well as to aid in the diagnosis of abnormalities resulting from these diseases. [18][19][20] In silicosis, de Mesquita Júnior et al 21 and Sá et al 22 reported that the reduction of spirometric parameters promoted increased resistive properties, decreased reactive properties and decreased homogeneity of the respiratory system measured by FOT.…”