Asbestosis is a type of interstitial pulmonary fibrosis caused by asbestos exposure. Occupational exposure such as for:
- Textile and construction workers who do asbestos abatement (Plumbers, Pipefitters, Electricians, Carpenters and Welders)
- Brake repairs
- Secondhand exposure may occur among family members of exposed workers and among people who live close to mines.
NOTE: Asbestosis- related disorders are caused by inhalation of asbestos fibers. The disorders include asbestosis, lung carcinoma, non malignant pleural plaque formation and thickening, benign pleural effusions, and mesothelioma. Asbestosis and mesothelioma both cause progressive dyspnea, as well as extensive effusions and plaques. Diagnosis is based on history and chest x-ray or CT findings and, in the case of cancer, tissue biopsy. Treatment is supportive care as for diffuse interstitial fibrosis, except for cancer, which may require surgery, chemotherapy, or both.
Asbestos is a generic term for several different mineral silicates: Chrysolite, Amosite, Anthophyllite, and Crocidolite
PATHOPHYSIOLOGY OF ASBESTOSIS
- Pulmonary fibrosis is initiated by injury to epithelial and mesothelial cells by asbestos fibers through formation of reactive oxygen intermediates
- Amount of injury is directly related to intensity and duration of exposure.
- After moderates to severe exposure, it usually takes at least 10 years before disease manifests.
- Asbestos fibers may also be directly toxic to lung tissue. Risk of disease is generally related to duration and intensity of exposure and type, length and thickness of inhaled fibers.
SIGNS AND SYMPTOMS OF ASBESTOSIS
- Asbestosis is initially asymptomatic but can cause progressive tachypnea, dyspnea, nonproductive cough and fatigue.
- The disorder progresses in more than 10% of patients even after cessation of exposure.
- Advanced asbestosis may cause clubbing and cyanosis of digits, bibasilar and expiratory dry crackles, and, in severe cases, symptoms and signs of right ventricular failure ( cor pulmonale).
DIAGNOSIS OF ASBESTOSIS
Work up should include:
- Chest x-ray
- Past exposure indicated by pleural plaques
- Benign pleural effusion
- Indistinct heart border, or “ground glass” appearance in lung fields, seen in some cases.
- Diagnosis is based on history of exposure and chest x-ray or chest CT. Chest x-ray shows linear reticular opacities signifying fibrosis, usually in the peripheral lower lobes.
- Preferably chest CT
- Thin silicon chest CT is useful when asbestosis is a likely diagnosis. CT is also superior to chest x-ray in identifying pleural abnormalities.
- Pulmonary function test
- Restrictive pattern with a decrease in lung volumes.
- Flow rates commonly reduced less than would be predicted on the basis of volume reduction.
- Reduced diffusion capacity
- Sometimes, bronchoalveolar lavage or lung biopsy
- On rare occasions when the diagnosis of asbestosis hinges on demonstration of asbestos bodies and fibers to document exposure, BAL should be performed if sputum analysis is negative.
- Bronchoalveolar lavage or lung biopsy is indicated only when noninvasive measures fail to provide conclusive diagnosis
TREATMENT OF ASBESTOSIS
No specific treatment exists.
- Supportive care as for diffuse interstitial fibrosis
- Smoking cessation
- Prevent further exposure
- Prompt attention to respiratory infections
- Early detection of hypoxemia and right ventricular failure leads to use of supplemental O2 and treatment of heart failure. Pulmonary rehabilitation can be helpful for patients with impairment.
PREVENTION OF ASBESTOSIS
Preventive measures include:
- Eliminating exposure, asbestos abatement in occupational and nonoccupational settings
- Smoking cessation and pneumococcal and influenza vaccination. Smoking cessation is particularly important in light of the multiplicative risk of lung cancer in patients who have both tobacco smoke and asbestos exposure.
COMPLICATIONS OF ASBESTOSIS
- Chronic obstructive pulmonary disease
- Congestive heart failure
- Increased risk of mesothelioma
- Increases risk of lung cancer
PROGNOSIS OF ASBESTOSIS
- Prognosis varies. A number patients have no or mild symptoms and do well, while some develop progressive dyspnea and a few develop respiratory failure, right ventricular failure, and cancer.
- Lung cancer (usually non-small cell lung carcinoma) develops in patients with asbestosis at 8 to 10 times the rate of those with no asbestosis and is especially common in workers exposed to amphibole fibers, although all forms of inhaled asbestos have been related with an elevated cancer risk. Asbestos and smoking have synergistic effect on lung cancer risk.
- Mortality due to malignancy was 5 times higher than expected
- Deaths attributed to lung cancer were 8 times higher than expected.