Incremental value of oblique chest radiographs in the diagnosis of asbestos-induced pleural disease

To assess the value of oblique chest radiographs in the diagnosis of asbestos-related pleural disease, we identified 100 asbestos-exposed construction workers and provided separate interpretations of the postero-anterior (PA), left anterior oblique (LAO), and right anterior oblique (RAO) projections using the International Labour Office (ILO) system. We found that the LAO projection identified left-sided pleural thickening more effectively than the PA view and the RAO view improved diagnosis of right-sided disease comparably. Of 62 cases of bilateral pleural thickening, only 43 (68%) were diagnosed by the PA projection alone. The increased diagnostic efficiency of approximately 50% in identifying bilateral pleural thickening appears to justify the routine use of oblique chest films in screening asbestos-exposed populations. Since bilateral pleural thickening among asbestos-exposed workers is an indicator of significant asbestos exposure and increased risk of other asbestos-induced conditions, early detection of this abnormality can lead to interventions designed to reduce asbestos-related morbidity and mortality.     

Asbestos exposure and radiological abnormalities among maintenance and custodian workers in buildings with friable asbestos-containing materials

Objectives Few studies have been carried out to evaluate the respiratory effects of asbestos exposure of custodian and maintenance workers.Methods By a multicentre cross-sectional study, 277 custodian and maintenance employees working in buildings with friable asbestos-containing materials and 87 unexposed subjects were studied for radiological abnormalities by use of the International Labour Office (ILO) classification of radiographs of pneumoconiosis, in relation to parameters of asbestos exposure.Results The cumulative asbestos exposure index was generally low (fewer than 5 fibres/ml × years in 82.3% of exposed workers). On multivariate analysis, pleural thickening was significantly related to latency since onset of exposure to asbestos in exposed workers, after adjustment for age, body mass index and tobacco smoking.Conclusions Asbestos exposure of custodian and maintenance employees in buildings with friable asbestos-containing materials might be associated with an excess of pleural thickening on chest X-rays.     

Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests.

The lungs of 50 symptom free workers exposed to amosite and with normal pulmonary function tests were examined by high resolution computed tomography (HRCT). Twenty five had normal standard chest radiographs whereas the other 25 had radiographs interpreted as near normal (International Labour Office profusion score < 0/1 or suspected pleural plaques). In 13 of the workers the results of HRCT were negative; in 22 pleural plaques were found, in five there was only parenchymal involvement, and 10 had both pleural and parenchymal changes. The mean duration of exposure to amosite was significantly longer for the subjects with parenchymal signs than for those with normal parenchyma and for the workers with pleural plaques than for those with normal pleura and lung parenchyma. The prevalence of identified pleural and parenchymal abnormalities in the 50 workers was also significantly higher than in a reference group without exposure to asbestos. It is concluded that HRCT may detect initial lung and pleural involvement in symptom free workers exposed to amosite and the mean duration of exposure is longer for subjects with parenchymal or pleural involvement.     

High-resolution computed tomography abnormalities in ex-insulators annually exposed to asbestos dust

BACKGROUND: characterize To the effects of high asbestos exposure during annual periods of insulation. METHOD: 170 ex-workers underwent clinical examination, spirometry, standard chest X-rays and high-resolution computed tomography (HRCT). Asbestos exposure was retrospectively assessed for latency, duration, and intensity. RESULTS: Sixty-six percent of these workers were annually exposed to high concentrations of asbestos dust. Respiratory symptoms were mild. One hundred and nineteen subjects had pleural or pulmonary changes on HRCT, compatible with asbestos exposure. Localized pleural thickening was found in 113 subjects (66.5%); pulmonary nodules or lines in 35 (20.6%). The presence of pleural plaques was linked to intensity of asbestos exposure (P <.01), and length of employment (P <.05). Parenchymal lesions were related to intensity (P <.05) and duration of exposure (P <.05). Lung function of subjects with X-ray changes was not significantly altered. CONCLUSIONS: Annual asbestos exposure led to a high prevalence of pleural plaques and to mild parenchymal anomalies.     

The usefulness of computed tomography in detecting asbestos-related pleural abnormalities in people who had indeterminate chest radiographs: the Libby, MT, experience

This epidemiological study was conducted to determine whether high-resolution computed tomography (HRCT) is useful to screen for pulmonary abnormalities in people exposed to vermiculite containing asbestos. During June-September 2001, we evaluated HRCT of 353 people in Libby, MT, who had been exposed to asbestiform minerals associated with vermiculite. Of these, 334 participants of the summer 2000 medical testing program underwent HRCT of the chest at St. John's Lutheran Hospital and 19 eligible people who recently had undergone an HRCT scan at the same facility and under the same testing protocol allowed the study reviewers to use that scan. All 353 study participants were former vermiculite mine/mill workers (n = 55), their household contacts (n = 99), and people exposed to vermiculite through recreational or other activities (n = 199). Participants' 2000 medical testing results indicated only one of the three B-reader chest radiograph reviewers had reported a pleural abnormality (indeterminate chest radiograph). Three expert computer tomography (CT) scan evaluators reviewed the HRCT scans and identified pleural abnormalities in 98 (27.8%) of the 353 participants whose previous chest radiographs were classified indeterminate. Of these 98 people, 69 (70.4%) were either former vermiculite mine/mill workers or household contacts, and 40 (40.8%) showed pleural calcification on HRCT. Thirty out of the 40 people with pleural calcification reported having no occupational exposure to either Libby vermiculite or asbestos. Our findings indicate that low-dose HRCT can be considered for screening certain former vermiculite mine/mill workers and their household contacts who have indeterminate chest radiographs and may be useful for diagnosing a suspicious finding on a chest radiograph, particularly in a high-risk person.     

Pulmonary function,smoking habits,and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos

To evaluate the presence of asbestos-related pleural and parenchymal abnormalities and their correlation with pulmonary function and smoking habits, 119 asbestos-exposed asymptomatic workers (mean age, 46.2 years; mean duration of asbestos exposure, 8.6 years; mean latency time, 21.6 years) with normal standard P-A chest radiographs were submitted to HRCT, CO-diffusing capacity, and pulmonary function tests. HRCT scans were normal only in 31 (26%) examined workers; 31 (26%) subjects showed both pleural and parenchymal involvement, and 50 (42%) and seven (6%) had exclusively pleural and parenchymal abnormalities, respectively. Based on CO-diffusing capacity and pulmonary function tests, no significant difference was demonstrated between workers with pleural lesions and subjects with normal pleura; however, lower values of FVC were observed in the nonsmoking workers with parenchymal abnormalities in comparison with nonsmoking subjects with normal parenchyma (78.2 vs. 89.7% of predicted values; p = 0.03 by student's two-tailedttest), and lower values of FEV₁/FVC in the smokers with parenchymal lesions with respect to smokers with normal parenchyma (93.7 vs. 100.2% of predicted values; p = 0.005 by student's two-tailedttest). In conclusion, our results demonstrate that HRCT may detect early parenchymal abnormalities which correlate with exposure to asbestos and respiratory function impairment, including a reduction in obstructive indices in smokers occupationally exposed to asbestos, without any clinically evident disease. © 1996 Wiley-Liss, Inc.     

High prevalence of reversible airway obstruction in asbestos-exposed workers

In this retrospective study of 97 male workers exposed to asbestos for 2-50 yr, data were collected on chest x-ray findings and lung function, including lung volumes, forced expiratory flow rates (i.e., forced expiratory volume in 1 sec [FEV1.0], forced expiratory flow measured between 25% and 75% of forced vital capacity [FEF(25-75%)]), airway resistance (R(aw)), carbon monoxide (CO)-diffusing capacity, and the existence of airway obstruction reversible by a beta-adrenergic agonist (RAO). The authors performed multiple-regression analyses to correlate the variations in lung function data with age, smoking habits, duration of asbestos exposure, and time since last exposure. Occupational activities of subjects that might induce specific lung abnormalities were also considered. No significant decrease was seen in lung volumes or CO-diffusing capacity; however, a decrease in FEV1.0 and an increase in R(aw) were measured in 65% of the subjects, and an isolated decrease in FEF(25-75%) occurred in only 18%. There was no difference in lung-function data between subjects who had chest x-ray signs of abnormalities (n = 59) and those who did not (n = 38). A significant relationship was found between the decrease in FEV1.0 and age; however, no correlation was noted between altered lung function and cigarette smoking, duration of asbestos exposure, or time since last exposure. RAO prevalence was higher (34%) than previously reported (9%) in subjects with chronic obstructive pulmonary disease (COPD) who were not exposed to asbestos or outdoor pollution. The RAO prevalence in asbestos-exposed workers was nearly the same as that measured in COPD subjects who lived downtown and who were exposed to outdoor pollution (36%). The high RAO prevalence in asbestos-exposed workers was found in 43% of subjects who were exposed only to asbestos, and in 33% of subjects who were also exposed to air pollution due to their occupational activities. It is hoped that the observations in this study will encourage practitioners to check for RAO in asbestos workers who use inhaled bronchodilators.     

High Prevalence of Reversible Airway Obstruction in Asbestos-Exposed Workers

In this retrospective study of 97 male workers exposed to asbestos for 2-50 yr, data were collected on chest x-ray findings and lung function, including lung volumes, forced expiratory flow rates (i.e., forced expiratory volume in 1 sec [FEV_1.0], forced expiratory flow measured between 25% and 75% of forced vital capacity [FEF_25-75%]), airway resistance (R_aw), carbon monoxide (CO)-diffusing capacity, and the existence of airway obstruction reversible by a β-adrenergic agonist (RAO). The authors performed multiple-regression analyses to correlate the variations in lung function data with age, smoking habits, duration of asbestos exposure, and time since last exposure. Occupational activities of subjects that might induce specific lung abnormalities were also considered. No significant decrease was seen in lung volumes or CO-diffusing capacity; however, a decrease in FEV_1.0 and an increase in R_aw were measured in 65% of the subjects, and an isolated decrease in FEF_25-75% occurred in only 18%. There was no difference in lung-function data between subjects who had chest x-ray signs of abnormalities (n = 59) and those who did not (n = 38). A significant relationship was found between the decrease in FEV_1.0 and age; however, no correlation was noted between altered lung function and cigarette smoking, duration of asbestos exposure, or time since last exposure. RAO prevalence was higher (34%) than previously reported (9%) in subjects with chronic obstructive pulmonary disease (COPD) who were not exposed to asbestos or outdoor pollution. The RAO prevalence in asbestos-exposed workers was nearly the same as that measured in COPD subjects who lived downtown and who were exposed to outdoor pollution (36%). The high RAO prevalence in asbestos-exposed workers was found in 43% of subjects who were exposed only to asbestos, and in 33% of subjects who were also exposed to air pollution due to their occupational activities. It is hoped that the observations in this study will encourage practitioners to check for RAO in asbestos workers who use inhaled bronchodilators.     

Role of computed tomography in evaluating asbestos related lung disease

To find how computed tomography (CT) may be effectively used in individuals with suspected asbestos related lung disease 30 men with a history of exposure to asbestos were studied. All subjects underwent high kilovoltage posteroanterior and left lateral chest radiographs and chest CT. Eighteen were randomly selected asbestos workers referred for routine surveillance. The remaining 12 were patients who had been referred for investigation of respiratory symptoms or abnormal routine chest radiograph, or both, and found to have chest radiographic changes compatible with asbestos related lung disease. In the group referred for routine surveillance both pleural shadowing and pulmonary shadowing were shown on CT but not chest radiographs in only one case. Five were thought to have pleural shadowing on chest radiographs but this was confirmed on CT in only one case. All 12 patients referred for investigation showed pleural shadowing on chest radiographs; this was confirmed in all cases on CT which also showed unsuspected pulmonary shadowing in five cases. These findings suggest that it is not appropriate to use chest CT routinely in all asbestos workers referred for routine surveillance. When CT is used selectively in those with pleural shadowing on plain chest radiography, however, it is helpful in refuting or confirming the presence of pleural disease and may show unsuspected pulmonary shadowing.     

Role of computed tomography in evaluating asbestos related lung disease.

To find how computed tomography (CT) may be effectively used in individuals with suspected asbestos related lung disease 30 men with a history of exposure to asbestos were studied. All subjects underwent high kilovoltage posteroanterior and left lateral chest radiographs and chest CT. Eighteen were randomly selected asbestos workers referred for routine surveillance. The remaining 12 were patients who had been referred for investigation of respiratory symptoms or abnormal routine chest radiograph, or both, and found to have chest radiographic changes compatible with asbestos related lung disease. In the group referred for routine surveillance both pleural shadowing and pulmonary shadowing were shown on CT but not chest radiographs in only one case. Five were thought to have pleural shadowing on chest radiographs but this was confirmed on CT in only one case. All 12 patients referred for investigation showed pleural shadowing on chest radiographs; this was confirmed in all cases on CT which also showed unsuspected pulmonary shadowing in five cases. These findings suggest that it is not appropriate to use chest CT routinely in all asbestos workers referred for routine surveillance. When CT is used selectively in those with pleural shadowing on plain chest radiography, however, it is helpful in refuting or confirming the presence of pleural disease and may show unsuspected pulmonary shadowing.     

A new high resolution computed tomography scoring system for pulmonary fibrosis, pleural disease, and emphysema in patients with asbestos related disease.

The aim of this study was to describe a scoring system for high resolution computed tomographic (HRCT) scans analogous to the International Labour Office (ILO) scoring system for plain chest radiographs in patients with asbestos related disease. Interstitial fibrosis, pleural disease, and emphysema were scored, the reproducibility and the interobserver agreement using this scoring system were examined, and the extent of the various types of disease was correlated with measurements of lung function. Sixty asbestos workers (five women and 55 men) mean age 59 (range 34-78) were studied. The lungs were divided into upper, middle, and lower thirds. An HRCT score for the extent of pleural disease and pulmonary disease in each third was recorded in a way analogous to the International Labour Office (ILO) method of scoring pleural and parenchymal disease on chest radiographs. A CT score for the extent of emphysema was also recorded. Pleural disease and interstitial fibrosis on the plain chest radiographs were assessed according to the ILO scoring system. A chest radiographic score for emphysema analogous to that used for HRCT was also recorded. Two independent readers assigned HRCT scores that differed by two categories or less in 96%, 92%, and 85% compared with 90%, 78%, and 79% of cases for chest radiographs for fibrosis, emphysema, and pleural disease respectively. There was better intraobserver repeatability for the HRCT scores than for the chest radiograph scores for all disorders. Multiple regression analysis showed that scores for interstitial fibrosis, emphysema, and pleural disease on chest radiographs and HRCT correlated to a similar degree with impairment of lung function.     

A new high resolution computed tomography scoring system for pulmonary fibrosis, pleural disease, and emphysema in patients with asbestos related disease.

The aim of this study was to describe a scoring system for high resolution computed tomographic (HRCT) scans analogous to the International Labour Office (ILO) scoring system for plain chest radiographs in patients with asbestos related disease. Interstitial fibrosis, pleural disease, and emphysema were scored, the reproducibility and the interobserver agreement using this scoring system were examined, and the extent of the various types of disease was correlated with measurements of lung function. Sixty asbestos workers (five women and 55 men) mean age 59 (range 34-78) were studied. The lungs were divided into upper, middle, and lower thirds. An HRCT score for the extent of pleural disease and pulmonary disease in each third was recorded in a way analogous to the International Labour Office (ILO) method of scoring pleural and parenchymal disease on chest radiographs. A CT score for the extent of emphysema was also recorded. Pleural disease and interstitial fibrosis on the plain chest radiographs were assessed according to the ILO scoring system. A chest radiographic score for emphysema analogous to that used for HRCT was also recorded. Two independent readers assigned HRCT scores that differed by two categories or less in 96%, 92%, and 85% compared with 90%, 78%, and 79% of cases for chest radiographs for fibrosis, emphysema, and pleural disease respectively. There was better intraobserver repeatability for the HRCT scores than for the chest radiograph scores for all disorders. Multiple regression analysis showed that scores for interstitial fibrosis, emphysema, and pleural disease on chest radiographs and HRCT correlated to a similar degree with impairment of lung function.     

Increased body mass index is related to apparent circumscribed pleural thickening on plain chest radiographs

BACKGROUND: Diffuse pleural thickening and pleural plaques are the commonest radiological manifestations of asbestos exposure. Differentiation between subpleural fat and non-calcified pleural plaques is important clinically and medico-legally. This study aims to determine if apparent circumscribed pleural thickening on chest radiographs is related with obesity. METHODS: Surveillance chest x-rays of 693 former asbestos workers were read with the ILO classification. Subjects with costophrenic angle obliteration (n = 57) were analyzed separately. The remaining subjects were subdivided according to their body mass index (BMI): Group 1 < 26 kg/m(2); Group 2 26-30 kg/m(2); Group 3 > 30 kg/m(2). RESULTS: Baseline characteristics, asbestos exposure, and profusion scores were evenly distributed. BMI of > 30 kg/m(2) was associated with a higher prevalence of pleural thickening on CXR (Gp1 = 8.5%; Gp2 = 9.3%; Gp3 = 18.3%). This relationship was strongest in the subgroups with 25-50% of the lateral chest wall involved and pleural thickness of < 10 mm. CONCLUSIONS: Obesity (BMI > 30 kg/m(2)) is related to apparent circumscribed pleural thickening on CXR, especially thin (< 1 cm) shadows covering 25-50% of the lateral chest wall.     

Computed tomography in the early detection of asbestosis.

Computed tomography (CT; both conventional (CCT) and high resolution (HRCT)) scans of the thorax were evaluated to detect early asbestosis in 61 subjects exposed to asbestos dust in Québec for an average of 22(3) years and in five controls. The study was limited to consecutive cases with chest radiographs of the International Labour Organisation categories 0 or 1 determined independently. All subjects had a standard high kilovoltage posteroanterior and lateral chest radiograph, a set of 10-15 1 cm collimation CCT scans and a set of three to five 2 mm collimation HRCT scans in the upper, middle, and lower lung fields. Five experienced readers independently read each chest radiograph and sets of CT scans. On the basis of three to five readers agreeing for small opacities of the lung parenchyma, 12/46 (26%) negative chest radiographs were positive on CT scans, but 6/18 (33%) positive chest radiographs were negative on CT scan. On the basis of four to five readers agreeing on a chest radiograph, 36/66 (54%) subjects were normal (group A), 17/66 (26%) were indeterminate (group B), and 13/66 (20%) were abnormal (group C). By the combined readings of CCT and HRCT, 4/31 (13%) asbestos exposed subjects of group A were abnormal (p < 0.001), 6/17 (35%) of group B were abnormal, and in group C, 1/13 (8%) was normal, 2/13 were indeterminate, and 10/13 (77%) were abnormal. Separate readings of CCT and HRCT on distinct films in 14 subjects showed that all cases of asbestosis were abnormal on both CCT and HRCT. Inter-reader analyses by kappa statistics showed significantly better agreement for the readings of CT than the chest radiographs (p < 0.001), and for the reading of CCT than HRCT (p < 0.01). Thus CT scans of the thorax identifies significantly more irregular opacities consistent with the diagnosis of asbestosis than the chest radiograph (20 cases on CT scans v 13 on chest radiographs when four to five readers agreed, 13% of asbestos exposed subjects with normal chest radiographs or 21% of asbestos exposed subjects with normal or near normal chest radiographs. It decreased the number of indeterminate cases significantly from 17 on chest radiographs to 13 on CT scans. All cases of asbestosis detected only on CT scans were similarly seen on CCT and HRCT and did not have significant changes in lung function. The CT scans significantly reduced the inter-reader variability, despite the absence of ILO type reference films for these scans.     

Progression of pleural and parenchymal disease on chest radiographs of workers exposed to amosite asbestos.

OBJECTIVES: To determine predictors of progression of pleural and parenchymal disease on the chest radiographs of workers exposed to a short term, intense exposure of amosite asbestos. METHODS: The first and last of a series of chest radiographs of 887 workers exposed to amosite was interpreted and coded according to International Labour Organisation (ILO) standards by two physicians. Significant predictors of disease progression were found by a linear stepwise regression analysis from among such variables as smoking history, latency (time since first exposure), duration and intensity of exposure, and cytology. RESULTS: Although most radiographs remained normal, some showed progression of disease with about twice as many patients with abnormalities on the last film. Various combinations of age, intensity of exposure, and time between films were significant predictors of pleural and parenchymal disease and progression of such disease. No predominance of one sided disease was noted. Cytology and smoking were unreliable predictors of disease. Most disease progression was minor, usually of less than two scoring categories. CONCLUSION: An intense, yet short, exposure to amosite asbestos can produce pleural and parenchymal changes on chest radiographs. The number of those affected roughly doubled over a period spanning 10 to 20 years after exposure. Age and intensity of exposure are the most important predictors of disease.     

Non-malignant asbestos-related diseases in Brazilian asbestos-cement workers

BACKGROUND: Production of asbestos-cement products in Brazil started in the 1940s, peaked in the 60-70s and is still an active industry. This study was designed to assess the non-malignant effects of asbestos exposure in the asbestos-cement industry in Brazil. METHODS: A group of 828 former asbestos-cement workers enrolled in a cross-sectional and cohort study of respiratory morbidity, submitted to a detailed occupational history, respiratory symptoms questionnaire, spirometry, PA chest x-ray, and high resolution computed chest tomography (HRCT). Asbestos exposure was assessed by years of exposure, cumulative exposure (a semi-quantitative method), and latency time from first exposure. Asbestosis and pleural thickening were assessed according to HRCT criteria. RESULTS: Asbestosis was present in 74 (8.9%) and pleural thickening in 246 (29.7%). Using the HRCT as the "best available evidence", it was shown that were more false negatives than false positives in the x-ray readings for parenchymal (21.6% false negatives, 4.2% false positives) and pleural (26.0% false negatives, 14.4% false positives) diseases due to asbestos. Latency time from first exposure was the best predictor for both asbestosis and pleural thickening. Subjects in the higher exposure groups presented lower levels of lung function. Obstructive defects were significantly related to smoking, shortness of breath, body mass index, and age, whereas restrictive defects were related to asbestosis, shortness of breath, and latency time. Chronic bronchitis increased with latency time in the three smoking groups and was significantly related to pleural thickening (OR 1.56 (1.00-2.42)). Shortness of breath was significantly associated with body mass index and pleural thickening (OR 1.30 (1.24-2.09)). CONCLUSIONS: Pleural thickening and asbestosis showed a significant association with latency time and exposure. FVC and FEV(1) decreased across increasing profusion with an added effect of pleural thickening. There was a significant and independent effect of exposure on lower levels of FVC and FEV(1). Obstructive defects were mainly related to smoking and restriction to asbestosis. Dust exposure and smoking were synergistic in increasing chronic bronchitis and shortness of breath report. Shortness of breath report was also related to pleural thickening and higher body mass index.     

High-resolution computed tomography in the early detection of asbestosis

Summary A group of 21 former asbestos sprayers was studied with high-resolution computed tomography (HRCT), and the findings were compared with radiographic, exposure and lung function variables. HRCT was superior to plain radiography in detecting parenchymal and pleural changes. It showed changes indicative of lung fibrosis, especially septal lines and parenchymal bands, in 9 of the 12 subjects (75%) with a plain radiographic category of 0/0 in the International Labour Office (ILO) 1980 classification of radiographs of pneumoconioses. The HRCT findings were classified according to a method developed by the authors, and an HRCT parenchymal score was calculated. The HRCT revealed pleural plaques in 19 of the 21 (90%) asbestos sprayers, whereas plain radiography detected pleural plaques in only 5 (24%) sprayers. Changes in the visceral pleura were detected twice as often with HRCT as with plain radiography. In the group without radiographic evidence of lung fibrosis (ILO < 1/0) and without evidence of emphysema in either the radiographs or the HRCT examination, there was a correlation between the HRCT parenchymal score and diffusion capacity (r = –0.64, P = 0.03) and total lung capacity (r = –0.61, P = 0.04). This finding indicates that parenchymal changes seen only with HRCT are of clinical importance. The study strongly suggests that for asbestos exposed workers with an ILO classification of < 1/0 and functional impairment, an HRCT examination should always be considered.     

胸膜增厚对石棉工人肺功能的影响

[目的]探讨胸膜增厚对石棉工人肺功能的影响。[方法]接触组为某温石棉厂134名男性工人，对照组为同一地区不接触粉尘、劳动强度与接触组大体相似的某仪表厂135名男性工人。对两组对象的肺功能测定和后前位X射线胸片检查结果进行对比分析。[结果]与对照组相比，在控制了肺内小阴影改变和累积吸烟量等混杂因素的影响后，石棉接触工人中胸膜正常细和双侧胸膜增厚组用力肺活量（FVC）和一秒钟用力呼气容积（FEV1）均显著下降（P〈0．05），单侧胸膜增厚组仅FVC显著下降（P〈0．05）；而与胸膜正常组相比，在控制了肺内小阴影改变、累积吸烟量和接尘年限等混杂因素的影响后，双侧胸膜增厚组FVC和FEV1显著下降（均为P〈0．05）；在控制了肺内小阴影改变、累积吸烟量和接尘年限等混杂因素的影响后，胸膜增厚范围与FVC呈负相关，与弥散系数（Kco）呈正相关（均为P〈0．05）。[结论]胸膜增厚范围越大，肺功能损害也越严重，呈限制性肺功能障碍的特征。     

The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan

BACKGROUND: Since asbestos has been widely used in Japanese building materials since 1960s, a large number of Japanese construction workers may be exposed to asbestos occupationally. METHODS: Among 2951 construction workers in Okayama, Japan, the prevalence of asbestos-induced pleural or pulmonary changes was examined by screening chest x-rays; these findings were confirmed by computed tomography (CT) scanning of the chest. RESULTS: Among 2951 construction workers, 168 (5.7%) were found to have significant findings for pleural plaque or pulmonary changes on chest x-ray. Seventy-four had both pleural plaque and asbestosis, 85 pleural plaques alone, and 9 asbestosis alone. In 11 subjects, pleural plaques were suggested by chest x-ray, but neither pleural plaque nor asbestosis was demonstrated by chest CT. Honeycombing as one of the characteristic findings of asbestosis was found in 29 subjects. Others showed subpleural spots or curvilinear shadow, which suggested the early stage of asbestosis. The occupations of these workers were carpenters (64), plasterers (27), and concrete board cutters (14). About 30% of the workers with these findings were aware that they were handling asbestos in activities such as installation of asbestos boards, and/or asbestos spraying. CONCLUSIONS: As the incidence of malignant mesothelioma and primary lung cancer associated with asbestos exposure are high, screening by chest CT is necessary for detecting asbestos-induced pulmonary and/or pleural lesions. Education for protection such as telling about the presence of asbestos in building materials is also necessary.     

Biphasic lung diffusing capacity: detection of early asbestos induced changes in lung function.

Asbestos related changes in the single breath carbon monoxide diffusing capacity (DLCO) were longitudinally analysed in 14 subjects exposed predominantly to chrysotile asbestos in an asbestos cement factory. These subjects were examined annually over the past nine years; their lung function was initially characterised with increased DLCO as the sole functional abnormality and they had normal chest radiographs. The radiological examination included a chest x ray film and, in the past two years, high resolution computed tomography (HRCT). A biphasic DLCO change was found: an initial increase followed by a relative decrease. The increase in DLCO was mainly caused by an increase in the membrane component (Dm). Indomethacin treatment applied after the sixth annual follow up significantly reduced DLCO and Dm. The decrease in DLCO correlated well with the parenchymal abnormalities found on HRCT, whereas the chest x ray film profusion score for small opacities (ILO classification) was unchanged. In conclusion, the data suggested that, as well as the absolute values of pulmonary function tests, the measurement of progression of functional parameters is essential in the assessment of pleural and parenchymal disease of the lung related to exposure to asbestos. High resolution computed tomography is suggested as the radiological method of choice in subjects with an isolated decrease in DLCO. Exposure to asbestos can be associated not only with a reduction in DLCO, but also with a temporary increase in DLCO caused by a subclinical inflammatory reaction.