Silicosis other diagnostic studies
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Lung Function Tests These tests are used in diagnosis and follow-up of patients to detect lung involvement, support the diagnosis of severity in each case, and guide future occupational choices. Spirometry is performed at the time of diagnosis and at check-ups for the evaluation of possible functional deterioration[1][2] Diffusion capacity is affected in the complicated forms of the disease and is sensitive to the presence of fibrosis.14 Static lung volumes can demonstrate a reduction in total lung volume associated with radiological involvement. These examinations are performed in patients with complicated silicosis or if abnormalities are detected on standard spirometry (consistent recommendation). Pulse oximetry and arterial blood gases are useful for establishing severity, since they can detect respiratory failure (PaO2<60 mmHg with SpO2<90%) in the more advanced cases.
- Pulmonary function testing (PFTs) are a key component of the evaluation of respiratory symptoms and abnormal radiographic findings. Typically, spirometry before and after bronchodilator, lung volumes, diffusing capacity for carbon monoxide (DLCO), and resting pulse oxygen saturation are obtained.
- Complete cardiopulmonary exercise testing may be helpful in evaluating patients with respiratory symptoms, particularly exertional dyspnea, who have a history of exposure to silica and whose resting lung function is normal.
- Workers exposed to respirable crystalline silica may have normal spirometry or may develop a range of pulmonary function test abnormalities [62,64-66]. In a study of 1028 foundry workers without chest radiograph abnormalities, there was a 1.1 mL per year decline in forced expiratory volume in one second (FEV1) for each mg per cubic meter (mg/m3) or mean silica exposure [64]. The presence of even mild radiographic findings of chronic or accelerated silicosis is associated, on average, with a greater degree of abnormality in pulmonary function. Spirometry shows a mixed picture of obstructive and restrictive ventilatory impairment with decreased FEV1 and FEV1/forced vital capacity (FVC) ratio [61]. (See "Overview of pulmonary function testing in adults".)
Pulmonary function, on average, worsens in association with worsening radiographic abnormalities of chronic or accelerated silicosis; cigarette smoking is often contributory [67]. PMF is associated with the worst pulmonary function abnormalities, including decreased compliance, decreased FEV1 and FEV1/FVC ratio, and decreased diffusing capacity for carbon monoxide (DLCO) [61,68]. In a number of studies using chest CT scan to evaluate lung parenchyma in chronic or accelerated silicosis, lung function abnormalities correlated better with the emphysematous changes of silicosis than the nodular changes of silicosis [69-71].
- Bronchoalveolar lavage — When acute silicosis is suspected, bronchoalveolar lavage (BAL) is used to exclude infection, eosinophilic pneumonia, and alveolar hemorrhage. In acute silicoproteinosis, BAL yields a thick, opaque (milky) effluent similar to that seen in pulmonary alveolar proteinosis. On cytologic examination, the macrophages in the BAL are foamy and the lipoproteinaceous material stains brightly positive with periodic acid-Schiff (PAS) reagent [3]
- Lung biopsy — The histopathology of acute silicosis is different from that of chronic or accelerated silicosis. Silicotic nodules are rarely seen, and, if present, are usually poorly developed. As described for BAL fluid, proteinaceous material fills the alveoli and consists largely of phospholipids or surfactant (or surfactant-like material) and stains with PAS reagent. The interstitium is thickened with inflammatory cells; a minimal amount of pulmonary fibrosis is typically present. Alveoli may be lined with prominent epithelial cells, the majority of which are hypertrophic type II pneumocytes [57]. In addition, desquamated pneumocytes, macrophages, and silica particles are found in the alveolar spaces. The histologic appearance of acute silicosis resembles that of idiopathic alveolar proteinosis (picture 1) [44]
References
- ↑ Mirabelli MC, London SJ, Charles LE, Pompeii LA, Wagenknecht LE (2012). "Occupation and three-year incidence of respiratory symptoms and lung function decline: the ARIC Study". Respir Res. 13: 24. doi:10.1186/1465-9921-13-24. PMC 3352304. PMID 22433119.
- ↑ Hochgatterer K, Moshammer H, Haluza D (2013). "Dust is in the air: effects of occupational exposure to mineral dust on lung function in a 9-year study". Lung. 191 (3): 257–63. doi:10.1007/s00408-013-9463-7. PMID 23568145.
- ↑ Nugent KM, Dodson RF, Idell S, Devillier JR (1989). "The utility of bronchoalveolar lavage and transbronchial lung biopsy combined with energy-dispersive X-ray analysis in the diagnosis of silicosis". Am Rev Respir Dis. 140 (5): 1438–41. doi:10.1164/ajrccm/140.5.1438. PMID 2817609.