Asbestosis (Asbestos pneumoconiosi) is a form of pneumoconiosis that develops as a result of prolonged inhalation of asbestos-containing dust and is characterized by diffuse fibrosis of the lung tissue. The clinic of asbestosis consists of general somatic disorders (malaise, fatigue, anorexia), signs of respiratory failure (shortness of breath, cyanosis, deformities of the terminal phalanges of the fingers), symptoms of respiratory damage (cough with mucous sputum, pleural syndrome). For the diagnosis of asbestosis, X-ray, CT scan of the lungs, spirometry, examination of sputum and bronchial washings are used. With asbestosis, supportive therapy is carried out (breathing exercises, physiotherapy, oxygen therapy).
Asbestos pneumoconiosis, or asbestosis – diffuse interstitial pneumosclerosis, caused by inhalation of asbestos particles. Along with talcosis, it belongs to silicosis- lung damage caused by exposure to lung tissue of silicic acid compounds. Asbestosis is observed in persons engaged in the extraction and processing of asbestos, as well as those working with asbestos-containing materials. The highest prevalence of asbestos pneumoconiosis is recorded in Canada, the country holding the world championship in asbestos reserves. The incidence of asbestosis increases in proportion to the increase in the time of contact with this material and averages 25-65% of cases. The danger of asbestosis lies not only in the development of diffuse fibrosis of the lung tissue, but also in terrible long-term consequences – an increased risk of developing asbestos-tuberculosis, mesothelioma of the pleura and peritoneum, adenocarcinoma of the lungs and stomach.
Causes of asbestosis
The immediate cause of this form of pneumoconiosis is prolonged inhalation of asbestos fibers. At the same time, asbestosis can develop both with work experience of less than 3 years, and 15-20 years after the termination of professional contact with asbestos dust. Asbestos is a fine-fibred mineral represented by hydrosilicate of magnesium, iron, calcium and sodium. Among the various varieties of asbestos, serpentine asbestos (chrysotile and antigorite), as well as amphibole asbestos (amosite, anthophyllite, crocidolite, tremolite) are of the greatest industrial importance – the latter are more fibrogenic and carcinogenic.
By the nature of their professional activity, workers employed in the asbestos mining and processing industry, construction, machine-building, shipbuilding, and aviation industries are in close contact with asbestos. These individuals constitute a high-risk group for the development of asbestosis. In addition, cases of asbestosis are known to occur with relatively short and mild exposure to asbestos-containing dust, for example, among women washing their husbands’ work clothes, or painters and electricians working in a room where asbestos-containing materials are used. In addition to professional exposure, household contact with asbestos is possible when using baby powder or asbestos textile products in residential buildings. It is known that smoking contributes to the occurrence of asbestosis, its rapid progression and severe course.
The mechanism of development of pulmonary fibrosis in asbestosis remains unclear. In pulmonology, it is customary to consider several versions of the onset of the disease: mechanical irritation of the lung tissue by asbestos needle fibers, damage to the alveoli by released silicon dioxide, the cytotoxic effect of asbestos on macrophages, the development of immunopathological reactions, etc. There are pulmonary and pleural forms of asbestosis. From the point of view of morphological changes in the lungs, asbestosis in its development goes through two phases: desquamative alveolitis and bronchiolitis. Pneumofibrosis (pneumosclerosis) is interstitial in nature, localized mainly in the middle and lower lobes, while emphysema is determined in the upper sections. Asbestosis is characterized by the presence of coarse pleural adhesions, sometimes pleural effusion. In the sputum, as well as in the lung parenchyma, the presence of asbestos bodies is detected, but this only confirms the fact of contact with asbestos dust, but is not the basis for establishing a diagnosis. In the pleural form of asbestosis, an isolated lesion of the pleura is noted with intact lung parenchyma.
The severity of asbestosis symptoms depends on the duration of exposure to asbestos particles and their concentration in the air. It is believed that with an occupational hazard of 3-4 years, a mild form of asbestosis develops, 8 years – moderate, 10 or more years – a severe form. Like the course of other pneumoconiosis, the clinic of asbestosis is characterized by chronic bronchitis and signs of pulmonary emphysema. All complaints and objective manifestations fit into three groups of symptoms: general somatic, signs of damage to the respiratory system and respiratory failure. Nonspecific symptoms include malaise, fatigue, pallor, weakness, anorexia, and weight loss. Often, warty outgrowths appear on the arms and legs – the so-called “asbestos warts”.
The involvement of the respiratory tract and pleura in the pathological process is indicated by the appearance of an unproductive cough or with scanty mucous sputum and severe pain in the chest. In severe cases, shortness of breath is expressed, cyanosis develops, thickening of the nail phalanges of the fingers is determined. Perhaps the development of exudative pleurisy, which has a serous or hemorrhagic character.
The course of asbestosis is often complicated by pneumonia, bronchiectasis, bronchial asthma, cor pulmonale, which aggravate the prognosis of pneumoconiosis. Most often, the death of patients occurs from respiratory and cardiopulmonary insufficiency. Asbestosis has been associated with rheumatoid arthritis. Against the background of asbestosis, patients are several times more likely to develop pulmonary tuberculosis (mainly its focal form), lung cancer, malignant mesothelioma of the peritoneum and pleura, cancer of the esophagus, stomach and colon.
Examination of patients with suspected pneumoconiosis is carried out by a pulmonologist with the participation of an occupational pathologist. In establishing the diagnosis of asbestosis, the study of the occupational route and the availability of data indicating exposure to asbestos dust play a decisive role. During auscultation, moist small bubbling (sometimes dry) rales, pleural rub are heard. Above the upper sections of the lungs, a box sound is determined percussion. In blood tests, accelerated ESR, hypergammaglobulinemia, RF, antinuclear antibodies, and a decrease in the level of oxygen in arterial blood can be detected.
Radiographic signs of asbestosis are linear-mesh deformation of the lung pattern, hilar fibrosis, pleural changes (plaques, adhesions, effusion), in the later stages – “honeycomb lung”. With dubious results of lung radiography, I resort to high-resolution CT of the lungs, which allows one to reliably consider subpleural linear, focal or irregularly shaped shadows.
The study of the function of external respiration in asbestosis indicates the predominance of restrictive disorders over obstructive ones (decrease in VC and respiratory volume, etc.). Due to the similarity of the clinical and radiological picture of asbestosis with other pneumoconiosis, a differential diagnosis is made with anthracosis, pulmonary hemosiderosis, stannosis, talcosis, fibrosing alveolitis, and other diseases. For this purpose, a microscopic analysis of sputum, a study of bronchial washings, a biopsy of lung tissue, in which asbestos bodies and fibers are found, is carried out.
Treatment of Asbestosis
Since changes in the lungs with asbestosis are irreversible, the disease is treated symptomatically. First of all, it is necessary to completely stop contact with asbestos, get rid of nicotine addiction, and exclude significant physical exertion. In order to avoid the addition of infections that aggravate respiratory failure, vaccination against influenza and pneumococcal infection is recommended. Supportive care is aimed at relieving symptoms; it includes postural drainage, chest massage, medicinal inhalations, breathing exercises, physiotherapy, and, if necessary, oxygen therapy. Drug treatment involves the use of inhaled bronchodilators, taking vitamins.
Forecast and prevention
With the development of complications, the prognosis for working capacity and a satisfactory quality of life is not encouraging: there is a high probability of disability, the development of severe concomitant diseases and the death of patients. Prevention of asbestosis consists of industrial and medical measures. The first of them involves the provision of the required sanitary and hygienic conditions and individual protection of workers, compliance with safety regulations. All workers in contact with asbestos or materials containing asbestos should undergo periodic medical examinations according to the established schedule. Considering the increased risk of developing tuberculosis and malignant tumors against the background of asbestosis, patients with an established diagnosis are recommended to be monitored by a phthisiatrician and an oncologist.
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