Workplace spirometry monitoring for respiratory disease prevention: a methods review.

This report reviews methods applicable in workplace spirometry monitoring for the identification of individuals with excessive lung function decline. Specific issues addressed include 1) maintaining longitudinal spirometry data precision at an acceptable level so that declines due to adverse physiological processes in the lung can be readily detected in an individual; 2) applying interpretative strategies that have a high likelihood of identifying workers at risk of developing lung function impairment; and 3) enhancing effectiveness of spirometry monitoring for intervention and disease prevention. Applications in ongoing computerized spirometry monitoring programs are described that demonstrate approaches to improving spirometry data precision and quality, and facilitating informed decision-making on disease prevention.

Comparing film and digital radiographs for reliability of pneumoconiosis classifications: a modeling approach.

RATIONALE AND OBJECTIVES: The International Labour Office (ILO) system for classifying chest radiographic changes related to inhalation of pathogenic dusts is predicated on film-screen radiography. Digital radiography has replaced film in many centers. Digital images can be printed on film ("hard copy") or can be viewed at a computer workstation ("soft copy"). The goal of the present investigation was to compare the inter-reader and intra-reader agreement of ILO classifications for pneumoconiosis across image formats. MATERIALS AND METHODS: Traditional film radiographs, hard copy digital images, and soft copy digital images from 107 subjects were read by six B readers. A multiple reader version of the inter-reader kappa statistic was compared across image formats. Intra-reader kappa comparisons were carried out using an iterative least-squares approach (unadjusted analysis) as well as a two-stage regression model adjusting for readers and subject-level covariates. RESULTS: There were few significant differences in the inter-reader and intra-reader agreement across formats. For parenchymal abnormalities, inter-reader and intra-reader kappa values ranged from 0.536 to 0.646, and 0.65 to 0.77, respectively. In the covariate-adjusted analysis film-screen radiography was generally associated with a numerically greater reliability (ie, higher kappa values) than the other image formats, although differences were rarely statistically significant. CONCLUSION: Film-screen radiographs, hard copy digital images, and soft copy digital images yielded similar reliability measures. These findings provide further support to the recommendation that soft copy digital images can be used for the recognition and classification of dust-related parenchymal abnormalities using the ILO system.

Comparison of storage phosphor computed radiography with conventional film-screen radiography in the recognition of pneumoconiosis.

Traditional film-screen radiography (FSR) has been useful in the recognition and evaluation of interstitial lung diseases, but is becoming increasingly obsolete. To evaluate the applicability of storage phosphor digital computed radiography (CR) images in the recognition of small lung opacities, we compared image quality and the profusion of small opacities between FSR and CR radiographs. We screened 1,388 working coal miners during the course of the study with FSR and CR images obtained on the same day from all participants. Each traditional chest film was independently interpreted by two of eight experienced readers using the International Labour Office (ILO) classification of radiographs of pneumoconiosis, as were CR images displayed on medical-grade computer monitors. The prevalence of small opacities (ILO category 1/0 or greater) did not differ between the two imaging modalities (5.2% for FSR and 4.8% for soft copy CR; p>0.50). Inter-reader agreement was also similar between FSR and CR. Significant differences between image modalities were observed in the shape of small opacities, and in the proportion of miners demonstrating high opacity profusion (category 2/1 and above). Our results indicate that, with appropriate attention to image acquisition and soft copy display, CR digital radiography can be equivalent to FSR in the identification of small interstitial lung opacities.

Classification of voluntary cough sound and airflow patterns for detecting abnormal pulmonary function.

BACKGROUND: Involuntary cough is a classic symptom of many respiratory diseases. The act of coughing serves a variety of functions such as clearing the airways in response to respiratory irritants or aspiration of foreign materials. It has been pointed out that a cough results in substantial stresses on the body which makes voluntary cough a useful tool in physical diagnosis. METHODS: In the present study, fifty-two normal subjects and sixty subjects with either obstructive or restrictive lung disorders were asked to perform three individual voluntary coughs. The objective of the study was to evaluate if the airflow and sound characteristics of a voluntary cough could be used to distinguish between normal subjects and subjects with lung disease. This was done by extracting a variety of features from both the cough airflow and acoustic characteristics and then using a classifier that applied a reconstruction algorithm based on principal component analysis. RESULTS: Results showed that the proposed method for analyzing voluntary coughs was capable of achieving an overall classification performance of 94% and 97% for identifying abnormal lung physiology in female and male subjects, respectively. An ROC analysis showed that the sensitivity and specificity of the cough parameter analysis methods were equal at 98% and 98% respectively, for the same groups of subjects. CONCLUSION: A novel system for classifying coughs has been developed. This automated classification system is capable of accurately detecting abnormal lung function based on the combination of the airflow and acoustic properties of voluntary cough.

Comparison of digital radiographs with film radiographs for the classification of pneumoconiosis.

RATIONALE AND OBJECTIVES: Digital chest imaging has replaced film chest radiographs in many centers, but the International Labour Organization classification system, which is the most widely used system for recognition and classification of dust-related abnormalities, is predicated on film chest radiographs. The purpose of this study was to evaluate the equivalency of digital chest radiographs (including both hard copy and soft copy) with film radiographs for the recognition and quantification of abnormalities consistent with pneumoconiosis using the International Labour Organization classification system. MATERIALS AND METHODS: Digital chest images and film images, obtained from 107 subjects with a range of parenchymal and pleural abnormalities, were classified in random order by six B readers. RESULTS: Readings of film and soft copy images were equivalent for small opacity profusion; readings of hard copy images had significantly greater prevalence of small opacities compared to film and soft copy. The prevalence of large opacities differed significantly among all three image formats: hard copy greater than film greater than soft copy. However, film and soft copy readings for large opacities did not differ significantly when images demonstrating the coalescence of small opacities that had not yet become a large opacity were grouped with large opacities. The prevalence of pleural abnormalities differed significantly among all three image formats: film greater than hard copy greater than soft copy. CONCLUSIONS: Film and soft copy images can be recommended for the recognition and classification of dust-related parenchymal abnormalities using International Labour Organization classifications. The role of digital radiography in reading for pleural abnormalities requires additional investigation.

A prospective cohort study among new Chinese coal miners: the early pattern of lung function change.

AIMS: To investigate the early pattern of longitudinal change in forced expiratory volume in 1 second (FEV1) among new Chinese coal miners, and the relation between coal mine dust exposure and the decline of lung function. METHODS: The early pattern of lung function changes in 317 newly hired Chinese underground coal miners was compared to 132 referents. This three year prospective cohort study involved a pre-employment and 15 follow up health surveys, including a questionnaire and spirometry tests. Twice a month, total and respirable dust area sampling was done. The authors used a two stage analysis and a linear mixed effects model approach to analyse the longitudinal spirometry data, and to investigate the changes in FEV1 over time, controlling for age, height, pack years of smoking, mean respirable dust concentration, the room temperature during testing, and the groupxtime interaction terms. RESULTS: FEV1 change over time in new miners is non-linear. New miners experience initial rapid FEV1 declines, primarily during the first year of mining, little change during the second year, and partial recovery during the third year. Both linear and quadratic time trends in FEV1 change are highly significant. Smoking miners lost more FEV1 than non-smokers. Referents, all age less than 20 years, showed continued lung growth, whereas the miners who were under age 20 exhibited a decline in FEV1. CONCLUSION: Dust and smoking affect lung function in young, newly hired Chinese coal miners. FEV1 change over the first three years of employment is non-linear. The findings have implications for both methods and interpretation of medical screening in coal mining and other dusty work: during the first several years of employment more frequent testing may be desirable, and caution is required in interpreting early FEV1 declines.

Rapidly progressive coal workers' pneumoconiosis in the United States: geographic clustering and other factors.

BACKGROUND: Despite significant progress made in reducing dust exposures in underground coal miners in the United States, severe cases of coal workers' pneumoconiosis (CWP), including progressive massive fibrosis (PMF), continue to occur among coal miners. AIMS: To identify US miners with rapidly progressive CWP and to describe their geographic distribution and associated risk factors. METHODS: Radiographic evidence of disease progression was evaluated for underground coal miners examined through US federal chest radiograph surveillance programmes from 1996 to 2002. A case of rapidly progressive CWP was defined as the development of PMF and/or an increase in small opacity profusion greater than one subcategory over five years. County based prevalences were derived for both CWP and rapidly progressive cases. RESULTS: A total of 886 cases of CWP were identified among 29 521 miners examined from 1996 to 2002. Among the subset of 783 miners with CWP for whom progression could be evaluated, 277 (35.4%) were cases of rapidly progressive CWP, including 41 with PMF. Miners with rapidly progressive CWP were younger than miners without rapid progression, were more likely to have worked in smaller mines (<50 employees), and also reported longer mean tenure in jobs involving work at the face of the mine (in contrast to other underground mining jobs), but did not differ with respect to mean underground tenure. There was a clear tendency for the proportion of cases of rapidly progressive CWP to be higher in eastern Kentucky, and western Virginia. CONCLUSIONS: Cases of rapidly progressive CWP can be regarded as sentinel health events, indicating inadequate prevention measures in specific regions. Such events should prompt investigations to identify causal factors and initiate appropriate additional measures to prevent further disease.

Respiratory symptoms among crab processing workers in Alaska: epidemiological and environmental assessment.

BACKGROUND: Crab processing workers may develop respiratory symptoms and specific IgE responses, but the risk factors have not been fully described. METHODS: In 1998, 107 workers at a crab processing facility completed a survey both at the beginning and end of the processing season. The surveys included standardized symptom questionnaires, spirometry, and serological testing, as well as measurement of workplace airborne crab allergens and microscopic analysis of aerosolized materials. RESULTS: Over the crab processing season, asthma-like symptoms developed in 26% of study participants and bronchitic symptoms in 19%. Only 9% of those with new asthma-like symptoms were IgE-sensitized to crab at the end of the season. Among the crab processing jobs, butchering and degilling workers had the highest incidence of respiratory symptoms. CONCLUSIONS: Both personal and process-related factors appear to affect the development of respiratory symptoms in crab processing workers. In this study, crab specific IgE was not detected in most of the workers with new symptoms. Published 2001 Wiley-Liss, Inc.

Lung area--volume models in relation to the recruitment--derecruitment of individual lung units.

The objective of this study was to reconsider some of the previous experimental results in terms of simple geometric models in order to determine if any of the apparent conflicts could be explained within a more unified concept. These models allow individual lung units and the entire lung to expand differently with regard to their area-volume relationship. The effect of a recruitment-derecruitment process as the lung inflates-deflates is also considered. Examples are used to illustrate how some of the apparent conflicts found in the literature may arise from whether or not recruitment and derecruitment take place during lung expansion and contraction.

Rapid declines in FEV1 and subsequent respiratory symptoms, illnesses, and mortality in coal miners in the United States.

Coal mine dust exposure is associated with accelerated loss of lung function. We assessed long-term health outcomes in two groups of underground coal miners who during previous mine surveys had shown either high rates of FEV1 decline (cases, n = 310) or relatively stable lung function (referents, n = 324). Cases and referents were matched initially for age, height, smoking status, and FEV1. We determined vital status for 561 miners, and obtained a follow-up questionnaire for 121 cases and 143 referents. Responses on the follow-up questionnaire were compared with those on the last previous mine health survey questionnaire. Cases showed a greater incidence of symptoms than did referents for cough, phlegm production, Grades II and III dyspnea, and wheezing, and greater incidences than referents of chronic bronchitis and self- reported asthma and emphysema. More cases than referents (15% versus 4%) left mining before retirement because of chest illnesses. After controls were applied for age and smoking, cases had twice the risk of dying of cardiovascular and nonmalignant respiratory diseases and a 3.2-fold greater risk of dying of chronic obstructive pulmonary disease than did referents. Rapid declines in FEV1 experienced by some coal miners are associated with subsequent increases in respiratory symptoms, illnesses, and mortality from cardiovascular and nonmalignant respiratory diseases.

Design strategies for longitudinal spirometry studies: study duration and measurement frequency.

Measuring the longitudinal change in FEV(1) is useful for assessing the adverse effects of respiratory exposures and pulmonary diseases. Investigators seek to estimate the "true" mean FEV(1) slope (mu(beta)) of an infinite population. The difference between the estimated mean FEV(1) slope (mu(beta)) and the true mean slope, resulting from biological variation and measurement errors, can be minimized by increasing the number of subjects (N), years of follow-up (D), or the frequency of measurements (P). We defined maximum error e(max) such that P[|mu(beta) - mu(beta)| < or = e(max)] = 0.95, and thus e(max) is one-half the width of the 95% confidence interval for mu(beta). We computed the values of e(max) on the basis of actual data obtained from 160 coal miners and working nonminers who had completed 11 spirometry measurements, using recommended equipment and procedures, at 6-mo intervals over 5 yr. Individual 5-yr FEV(1) slopes (Delta FEV(1)) were calculated by linear regression. For a range of values of N, D, and P, tables are provided for e(max), the magnitude of detectable differences in Delta FEV(1) between two groups, and the recommended number of subjects needed in each of two groups to reliably detect the anticipated differences in Delta FEV(1). The tables provide unique guidance for investigators in selecting among various study design options.

Asthma-like symptoms in wood product plant workers exposed to methylene diphenyl diisocyanate.

BACKGROUND: Diisocyanates, a group of highly reactive chemicals, have frequently been associated with occupational asthma. We evaluated respiratory health in workers at a new wood products manufacturing plant that uses methylene diphenyl diisocyanate (MDI), and was designed and operated with a goal of minimizing worker exposures. METHODS: Health surveys using standardized respiratory questionnaires were done prior to the initial use of diisocyanates in the plant, and semiannually thereafter for a period of 2 years. Other testing included occupational and work practice histories, serial peak flow measurements, spirometry, methacholine challenge, and measurement of specific IgE antibodies to MDI-albumin conjugate. RESULTS: Of 214 plant employees who participated in at least one health survey, a follow-up survey was also available from 178 employees (83%). New-onset asthma-like symptoms (NAS) were reported by 15 of 56 workers (27%) in areas with the highest potential for exposures to liquid MDI monomer and prepolymer, vs 0 of 43 workers in the lowest potential exposure areas (p = 0.001). In the areas with high potential exposure, NAS developed in 47% of workers who had noted MDI skin staining, vs 19% without skin stains (p = 0.07). Working around and cleaning up liquid MDI represented a significant risk for asthma-like symptoms in both current smokers and nonsmokers; work with finished wood products did not. Asthma-like symptoms were associated with variable airflow limitation (odds ratio [OR], 5.0; confidence interval [CI], 1.4 to 18.7) and specific IgE to MDI-albumin (OR, 3.2; CI, 1.1 to 9.0), but not with skin prick tests to common aeroallergens (OR, 1.1; CI, 0.5 to 2.7). CONCLUSIONS: During the first 2 years of operation, in a plant designed and operated to control exposure to diisocyanates, the development of asthma-like symptoms was reported in a relatively high proportion of the employees who worked with liquid MDI. To prevent asthma symptoms among workers, careful control of respiratory tract exposures associated with liquid MDI is important, especially during cleanup activities. Strict limitation of skin contact with diisocyanates may also be necessary.

Couriers of asthma: antigenic proteins in natural rubber latex.

Natural rubber latex (NRL) is a milky, white liquid containing the polymer cis-1,4-polyisoprene, derived from the laticifer cells of the rubber tree, Hevea brasiliensis. Reports of allergic reactions to NRL, ranging in severity from skin rashes to anaphylaxis and death, have been increasing. High rates of latex allergy are seen in children with spina bifida. Healthcare workers, especially those who frequently use powdered latex medical gloves, can develop NRL allergy and asthma, often resulting in considerable disability. Atopy and, possibly, pre-existing dermatitis predispose to sensitization and allergic symptoms. NRL protein antigens are found in many NRL products and also have been shown to bind to cornstarch glove-donning powders. Of the approximately 240 polypeptides in NRL, nearly 60 are antigenic, and nine have been identified and registered (Hev b 1&ndash9). Many natural latex antigens share epitopes with structural proteins and enzymes from other plant species. Current knowledge indicates that proposed reductions in total glove protein and limitations on the use of powder on NRL gloves are likely to result in a decline in the prevalence and severity of NRL allergies among healthcare workers.

Clinical evaluation, management, and prevention of work-related asthma.

Work-related asthma (WRA) is asthma that is attributable to, or is made worse by, environmental exposures in the workplace. WRA has become the most prevalent occupational lung disease in developed countries, is more common than is generally recognized, and can be severe and disabling. Identification of workplace exposures causing and/or aggravating the asthma, and appropriate control or cessation of these exposures can often lead to reduction or even complete elimination of symptoms and disability. This depends on timely recognition and diagnosis of WRA. In this review, the diagnostic evaluation has been organized in a stepwise fashion to make it more practical for primary care physicians as well as physicians specializing in occupational diseases and asthma. WRA merits more widespread attention among clinicians, labor and management health and safety specialists, researchers, health care organizations, public health policy makers, industrial hygienists, and others interested in disease prevention.

Discountinuous lung sounds and hysteresis in control and Tween 20-rinsed excised rat lungs.

In the past, the relationship between pulmonary hysteresis and a model of the recruitment-derecruitment of lung units has been explored (Cheng, W., DeLong, D.S., Franz, G.N., Petsonk, E.L., Frazer, D.G., 1995, Resp. Physiol. 102, 205-215). The recruitment process is characterized by a sequence of events which represents discrete configurational changes in lung structure. It is assumed that energy released during the opening of lung units is associated with the formation of discontinuous lung sounds. The goal of this study was to record tracheal sounds for lungs inflated from different end-expiratory pressures and to relate the sound power to the normalized hysteresis of individual pressure-volume (PL-VL) loops. PL-VL curves and lung sounds were recorded for control lungs and lungs rinsed with Tween 20 in order to estimate the role of alveolar surfactant on the recruitment-derecruitment process. Results indicate that there may be two populations of lung units, one which is altered by Tween 20 and another which is not. The population not affected by Tween 20 appears to be responsible for producing discrete lung sounds and may represent the opening of larger conducting airways. The second population, possibly within the respiratory zone, is affected by alterations in surface tension and contributes to pulmonary hysteresis, but, apparently, does not contribute significantly to lung sound power measured at the trachea.

Clinically important FEV1 declines among coal miners: an exploration of previously unrecognised determinants.

OBJECTIVES: The relation between occupational exposure to dust and loss of ventilatory lung function is now well established. However, many exposures during work and other activities might also have important roles in determining clinically important losses of lung function. In this study, we attempted to explore additional plausible determinants of exposures and other potential risk factors for clinically important decline in forced expiratory volume in 1 second (FEV1) during work in dusty trades. METHODS: The study was performed in 264 underground coal miners whose lung function had been followed up for an average of 11 years. With an extensive follow up questionnaire, miners were asked about their occupational and non-occupational exposures, smoking, personal and family medical history, and living conditions during childhood. RESULTS: Several variables of the mine environment (as well as previously recognised effects of mining work and region) were found to be associated with excess decline in FEV1, including work in roof bolting, exposure to explosive blasting, and to control dust spraying water that had been stored in holding tanks. Use of respiratory protection seemed to reduce the risk of decline in FEV1. Other factors that were found to be associated with declines in pulmonary function included smoking, body mass, weight gain, childhood pneumonia, and childhood exposure in the home to passive tobacco smoke and possibly smoke due to wood and coal fuels. Miners with excessive decline in FEV1 were less likely to be working in mining jobs at follow up. CONCLUSIONS: These findings suggest the existence of additional risk factors for decline in lung function in dusty trades, and may be useful in developing additional approaches to the prevention of chronic respiratory disease.

Bronchial responsiveness and five-year FEV1 decline: a study in miners and nonminers.

Increased nonspecific bronchial responsiveness (NSBR) may be a risk factor for the development of chronic airflow obstruction. We evaluated this hypothesis in a cohort of 378 underground coal miners and working nonminers. Methacholine testing was performed at the beginning and end of a 5-yr study period. Spirometry was repeated at 6-mo intervals and individual 5-yr FEV1 slopes were calculated by linear regression. Relationships between FEV1 slopes and NSBR were examined using multiple linear regression models, controlling for FEV1 level, smoking, and mining. Increasing NSBR at the initial survey was associated with a somewhat greater rate of subsequent FEV1 decline. Methacholine responders at the final survey had a considerably increased rate of decline during the previous years. Responsiveness status changed over the 5 yr in 22% of the subjects. Both the development and persistence of increased NSBR were strongly associated with higher rates of FEV1 decline. In contrast, FEV1 declines were not accelerated among workers with increased NSBR that reverted to normal. Smoking and mining were both independently associated with FEV1 declines, but did not substantially modify the effect of NSBR. Due to its variability over time, NSBR testing predicts lung function decline only in some individuals, and its value as a prognostic test for chronic airway disorders is limited. Because improvement in bronchial hyperresponsiveness was associated with a reduction in the rate of FEV1 loss, interventions directed at preventing or reducing nonspecific airway hyperresponsiveness should be investigated.

Weight gain and longitudinal changes in lung function in steel workers.

Associations among dust exposure, smoking habits, and demographic factors and longitudinal changes of lung function were assessed among male steel workers. Cohort descriptive data analysis was conducted in 541 steel workers who had performed spirometry at least twice between 1982 and 1991 (mean follow-up, 6.1 years). The annual change (slope) in FVC, FEV1, FEV1/FVC%, and in body weight was determined by simple linear regression. The Pearson correlation coefficient between weight change and spirometry changes was calculated. Comparisons were also done in 75 pairs of steel workers matched by age, height, initial FEV1, and smoking status, but whose FEV1 declines differed by > or = 60 mL/yr. The FEV1 and FVC declined an average of 44 and 50 mL/yr, respectively, for the cohort as a whole. The FEV1 and FVC declined 52 and 54 mL/yr for current smokers, 43 and 53 mL/yr for ex-smokers, and 36 and 43 mL/yr for nonsmokers, respectively. Increasing weight was highly correlated with accelerated decline in lung function (p<0.0001). In the matched pairs, mean slopes for FVC, FEV1, and FEV1/FVC ratio were -96 mL/yr, -95 mL/yr, and -0.40%/yr for the rapid decliners; and +5 mL/yr, +10 mL/yr, and +0.10%/yr for their partners (p<0.0001). Matched pair comparisons showed that the rapid decliners averaged a 4.313 kg weight gain, while their partners gained 1.044 kg during the follow-up period. The slope of weight gain was 0.708 kg/yr for rapid decliners and 0.191 kg/yr for comparison workers (p<0.0036). Weight gain, in addition to aging and cigarette smoking, was found to be associated with the longitudinal rate of decline in FVC, FEV1, and FEV1/FVC ratio.