Int Arch Occup Environ Health (2012) 85:623–630 DOI 10.1007/s00420-011-0708-6
ORIGINAL ARTICLE
On-site screening of farming-induced chronic obstructive pulmonary disease with the use of an electronic mini-spirometer: results of a pilot study in Brittany, France Stephane Jouneau • Arnaud Boche´ • Graziella Brinchault • Kristina Fekete • Stephanie Guillot • Sahar Bayat • Benoit Desrues
Received: 8 October 2010 / Accepted: 23 September 2011 / Published online: 11 October 2011 Ó Springer-Verlag 2011
Abstract Purpose Dairy farming is a risk factor for the development of chronic obstructive pulmonary disease (COPD). We assessed the prevalence of farming-induced COPD (FI-COPD) using a new screening device, and we analyzed symptoms and occupational risk factors.
S. Jouneau (&) A. Boche´ G. Brinchault K. Fekete B. Desrues Respiratory Department, Pontchaillou Hospital, Rennes 1 University, 2 Rue Henri Le Guilloux, 35033 Rennes, France e-mail:
[email protected] A. Boche´ e-mail:
[email protected] G. Brinchault e-mail:
[email protected] K. Fekete e-mail:
[email protected] B. Desrues e-mail:
[email protected] S. Jouneau IRSET, UPRES Equipe Associe´e 4427 SeRAIC, Rennes 1 University, Rennes, France S. Guillot Physiology Department, Pontchaillou Hospital, Rennes 1 University, Rennes, France e-mail:
[email protected] S. Bayat Medical Information Department, Pontchaillou Hospital, Rennes 1 University, Rennes, France e-mail:
[email protected] S. Bayat INSERM U936, Rennes 1 University, Rennes, France
Methods We performed on-site screening study of bronchial obstruction using an electronic mini-spirometer (EMS) on an entire population of dairy farmers (n = 147) from two villages in Brittany, France. Suspected bronchial obstruction (FEV1/FEV6 \0.8) was confirmed with standardized lung function tests (FEV1/FVC B0.7). We assessed past medical histories, respiratory symptoms, and occupational tasks of subjects with bronchial obstruction; asthmatics were defined as atopic and/or reversible; smoking-induced COPD patients were defined as non-reversible, non-atopic with smoking histories (C5 PY); and FI-COPD patients were defined as non-reversible, non-atopic, and non-smokers. Results Using the EMS, 30.6% (n = 45) of dairy farmers were suspected of bronchial obstruction and underwent standardized spirometry. The FEV1/FEV6 ratio and FEV1/ FVC ratio were in good agreement (r2 = 0.66, P \ 0.0001). The prevalence of confirmed bronchial obstruction was 9.5% (n = 14), which included 4 asthmatics, 3 smoking-induced COPD subjects, and 7 FI-COPD subjects. All the COPD patients were GOLD Stage II, and none were aware of their respiratory disease. Foddering duration was significantly higher in FI-COPD subjects compared with non-obstructive subjects, with 44 versus 17 min/day, respectively. Conclusions The EMS was a convenient mean of screening for bronchial obstruction, especially in on-site settings, and allowed us to diagnose FI-COPD in a nonspontaneously complaining dairy farmer population. Foddering was considered a significant risk factor. Keywords Farmer Chronic bronchitis Bronchial obstruction Dust exposure Chronic obstructive pulmonary disease Abbreviations COPD Chronic obstructive pulmonary disease
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EMS FEV1 FEV6 FI-COPD FVC PY
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Electronic mini-spirometer Forced expiratory volume in 1 s Forced expiratory volume in 6 s Farming-induced COPD Forced vital capacity Pack-year
Introduction Chronic obstructive pulmonary disease (COPD) is a major health problem and is expected to become the third leading cause of death worldwide by 2020 (Rabe et al. 2007). The most important risk factor for COPD is cigarette smoking, with 80–90% of patients diagnosed with COPD having a history of smoking. Beside tobacco exposure, occupational COPD has been reported, especially in farmers and farm workers (Balmes et al. 2003; Eduard et al. 2009). Accelerated decline in forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) has been observed in grain handlers (Enarson et al. 1985), swine confinement workers (Senthilselvan et al. 1997), and dairy farmers (Chaudemanche et al. 2003; Dalphin et al. 1998a, b). The mechanism of this ‘‘farming-induced COPD’’ (FI-COPD) is not clear. Farmers are exposed to a wide range of organic and inorganic dusts and gases (Dalphin et al. 1989; Linaker and Smedley 2002). Several exposure elements, including dust, ammonia, and endotoxin, have been associated with respiratory symptoms in farmers (Donham et al. 2000, 1995; Eduard et al. 2001, 2004; Kirychuk et al. 2006; Thelin et al. 1984; Vogelzang et al. 1998). Farmers do not seem to complain about respiratory symptoms until advanced stages of the disease, and they may be more reluctant to consult their medical doctor than the general population. Therefore, it would be beneficial to diagnose FI-COPD at an earlier stage in these specific patients to improve prevention strategies and decelerate the decline in lung function (Decramer et al. 2009). Electronic mini-spirometers (EMS) are pocket-size electronic tools that are easy to transport to working sites. The devices have been validated to screen patients for bronchial obstruction in primary care settings (Hankinson et al. 2003; Kaufmann et al. 2009). The FEV1/FEV6 (forced expiratory volume in 6 s) ratio is nearly as strong an independent predictor of decline in lung function as the FEV1/FVC ratio (Enright et al. 2002; Rosa et al. 2007). FEV1/FEV6 can be used as a valid alternative to FEV1/ FVC in diagnosing airway obstruction (Collectif Capital Souffle 2007; Jing et al. 2009; Lundgren et al. 2007). An exhalation maneuver for 6 s is easier to accomplish in most
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patients. Thus, the results seem to be more reproducible and less prone to error compared with FVC. However, mild forms of airflow limitation can be missed because of possible underestimation when using a cutoff point of 0.7 for FEV1/FEV6 (Vandevoorde et al. 2006). As previously reported, it seems reasonable to use a 0.8 cutoff point in comparison to standardized pulmonary function tests when using FEV6 instead of FVC (Kaufmann et al. 2009). To screen on-site the farmers for FI-COPD, we used an EMS on an entire population of dairy farmers in two villages in Brittany, France. In addition, we measured the mean daily duration of different occupational ‘‘dusty’’ tasks to assess their role as risk factors.
Materials and methods This was a prospective observational study performed between January 2008 and January 2009. One district was chosen because of its high prevalence of dairy farming (Balaze´ and Saint M’Herve´, Ille et Vilaine, France). One investigator performed both the questionnaires and screenings using the EMS (A. B.), and only one local respiratory physician performed the standardized lung function tests (K. F.). Subjects Using a database from the ‘‘Mutualite´ Sociale Agricole’’ (MSA, National health insurance for farmers), 216 subjects were identified as dairy farmers in this specific area. Twenty-nine subjects were excluded because their occupation as dairy farmers was \10 years, or they were retired for more than 5 years. Thirty-seven subjects were excluded to avoid exposure bias because they were involved in multiple farming tasks, mainly swine farming. Three other subjects were also excluded: one refused to participate in the study; one had recent abdominal surgery, preventing deep breathing; and one died prior to the study. Finally, 147 subjects were recruited in this study, which was approved by the local ethics committee (registration number 10.12-1). Informed consent was obtained from all subjects. Questionnaire The 147 subjects enrolled were asked about their age, gender, past medical history (personal and familial), smoking history, and atopy [defined by the presence of asthma and/or chronic allergic rhinitis (complaining with this symptom for more than 3 months) and/or eczema]. Respiratory symptoms were reported [chronic cough ([8 weeks), chronic bronchitis and chronic dyspnea
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([3 months)] as previously described (Dalphin et al. 1989). The different agricultural tasks and their daily duration were also assessed: milking, straw litter spreading, and foddering. We also asked the farmers concerning the use of filter masks, duration of tractors use, and time spent in front of open fireplaces (biomass fuel) at home and/or in the farm’s buildings. Spirometry Subjects underwent electronic mini-spirometry using a PiKo-6Ò device with 3 consecutive measurements per subject, with the best measure recorded for analysis. The PiKo-6Ò device is a new, simple, electronic screening tool, which measures FEV1, FEV6, and FEV1/FEV6 (e-Ness, France). FEV6 was the exhaled volume within the first 6 s of forced exhalation. Results of exhalation maneuvers were immediately displayed on the PiKo-6Ò device. An audible signal indicated that the required duration of exhalation maneuvers was reached. Furthermore, there was visual feedback concerning the quality of the maneuver. Most of the patients were able to handle the device after the first maneuver; therefore, they could perform the subsequent maneuvers on their own (Kaufmann et al. 2009). According to previous studies and per French recommendations, subjects with FEV1/FEV6 [0.8 were considered normal, and subjects with a ratio \0.8 (at risk subjects) underwent standardized pulmonary function tests with a single respiratory physician (Collectif Capital Souffle 2007; Enright et al. 2002; Hankinson et al. 2003; Kaufmann et al. 2009). We have chosen the high cutoff point of 80% for FEV1/ FEV6 to avoid overlooking any slight airflow limitation, thus accepting a high rate of false-positive results (Kaufmann et al. 2009). Standardized pulmonary function tests were performed with calibrated spirometers (Masterscreen, VIASYS Healthcare, Germany) according to the American Thoracic Society and European Respiratory Society (ATS/ ERS) recommendations (Miller et al. 2005). Subjects with FEV1/FVC B0.7 (pre-bronchodilator values) were considered obstructive patients and reversibility tests were performed. Obstructive patients’ classification In obstructive patients, asthmatics were defined as patients with positive reversibility tests during spirometry [postbronchodilator FEV1 increase C200 ml and C12% (Pellegrino et al. 2005)] and/or atopic; smoking-induced COPD subjects were defined as non-reversible and non-atopic subjects with smoking histories C5 pack-years (PY), and farming-induced COPD subjects were defined as nonreversible, non-atopic, and non-smokers (\5 PY).
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Data analysis Quantitative variables were expressed as mean values with standard deviations. We assumed non-Gaussian distribution and used the Mann–Whitney test for continuous variables (i.e., milking, straw litter spreading, foddering, duration of tractors use, and time spent in front of open fireplaces). We used Fisher’s exact test for dichotomous variables (atopy, symptoms, use of filter masks). Bland– Altman plots were used to evaluate the degree of agreement between FEV1/FEV6 and FEV1/FVC ratios. Data analysis was performed using the SPSSÒ 17.0 statistical software package. Values of P \ 0.05 were regarded as significant.
Results Study population Figure 1 describes the study population. One hundred and forty-seven dairy farmers were included; 102 had a FEV1/ FEV6 [0.8 and were considered as non-obstructive. The remaining 45 subjects underwent standardized pulmonary function tests. The prevalence of bronchial obstruction (FEV1/FVC B0.7) was 9.5% (n = 14). These patients are divided as follows (Fig. 1): 4 asthmatics, 3 smokinginduced COPD patients, and 7 farming-induced COPD (FICOPD) patients; only 3 asthmatics were aware of their diagnosis; none of the patients with COPD were aware of their respiratory disease before the study; and 4 patients (26%) were completely asymptomatic (2 FI-COPD and 2 asthmatics). In the 31 subjects considered as non-obstructive after spirometry, the mean FEV1/FVC ratio was 0.77 ± 0.03, and only 3 subjects had a FEV1/FVC ratio [0.8. Comparison of the two spirometric techniques In the ‘‘at risk’’ subjects defined by FEV1/FEV6 ratio \0.8 (n = 45), Fig. 2a shows the graphic correlation between FEV1/FEV6 and FEV1/FVC ratios (r2 = 0.66, P \ 0.0001). The two techniques (EMS and standardized pulmonary function test) are in good agreement (Fig. 2b). We describe in Table 1 that the number of subjects in each group is divided into FEV1/FEV6 B0.7 or[0.7 and FEV1/ FVC B0.7 or [0.7. In absolute values, the mean difference between FEV1/FEV6 and FEV1/FVC ratios was 0.03 ± 0.03 [range from 0 to 0.08] with several subjects having 0.71 or 0.72 for one method and 0.70 or 0.69 for the other method. In the obstructive population (FEV1/FVC B0.7, n = 14), Fig. 2c shows the graphic correlation between
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Fig. 1 Details of the study population. In total, 147 dairy farmers were included; 102 had FEV1/FEV6 [0.8 and were considered as non-obstructive. The 45 subjects remaining underwent spirometry. The prevalence of bronchial obstruction was 9.5% (n = 14). The subjects were divided as follows: 4 asthmatics, 3 smoking-induced COPD patients, and 7 farming-induced COPD patients (prevalence = 4.8%)
FEV1/FEV6 and FEV1/FVC ratios (r2 = 0.74, P \ 0.0001), which were in good agreement (Fig. 2d). Characteristics and symptoms The characteristics and symptoms of the farmer population (n = 147), divided into FI-COPD patients (n = 7) and non-obstructive subjects (n = 133), are described in Table 2. The mean age of FI-COPD patients was 50 ± 9 years. The FI-COPD patients were never-smokers. There was significantly more dyspnea in the FI-COPD patients compared with non-obstructive subjects (71% vs. 16%, P = 0.004). FI-COPD patients (as with the smokinginduced COPD patients) were GOLD Stage II with a mean FEV1 = 66.4 ± 6.6% of predicted values. No significant difference was observed between FI-COPD and smokinginduced COPD (FEV1 = 66.4 ± 6.6% vs. 61.3 ± 9.7%, P = 0.43). Occupational risk factors Daily duration of foddering (‘‘dusty’’ task) was significantly higher in FI-COPD patients compared with nonobstructive subjects; 44 versus 17 min/day (P = 0.02, Fig. 3a). In contrast, daily duration of straw litter
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spreading, another ‘‘dusty’’ task, is not different between FI-COPD patients and control subjects; 20 versus 15 min/ day (P = 0.23, Fig. 3b). Daily duration of milking is approximately 90 min/day in both groups (Fig. 3c). None of the farmers were using filter masks at the time of our screening study. The duration of tractor use and time spent in front of open fireplaces was not significantly higher in obstructive patients compared with non-obstructive subjects. In our study, open fireplaces were used by 42 subjects, which included only 2 obstructive patients with asthma.
Discussion To our knowledge, this on-site screening study of bronchial obstructions in a farmer population was the first using an EMS. We showed that in our dairy farmer population, the EMS was a convenient method of screening for bronchial obstructions, especially in an on-site setting due to its pocket-size. Furthermore, we observed a good correlation between FEV1/FEV6 and FEV1/FVC ratios. The prevalence of farming-induced COPD (FI-COPD) was close to 5%. All of the COPD patients were GOLD Stage II, therefore suitable for maintenance treatment, and were
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Fig. 2 Correlation between FEV1/FEV6 and FEV1/FVC ratios in the ‘‘at risk’’ subjects (FEV1/FEV6 \0.8, n = 45, Fig. 2a) diagnosed with the EMS and obstructive patients (n = 14, Fig. 2c) diagnosed with standardized pulmonary function tests. Figure 2b and d show Bland–Altman plots for the agreement between FEV1/ FEV6 and FEV1/FVC in the ‘‘at risk’’ subjects (n = 45) and the obstructive patients (n = 14), respectively
Table 1 Analysis of patients at risk for bronchial obstruction (FEV1/ FEV6 \0.8, n = 45) FEV1/FEV6 B0.7
FEV1/FEV6 [0.7
FEV1/FVC B0.7
8
7
FEV1/FVC [0.7
5
25
The subjects in each group are divided into FEV1/FEV6 B0.7 or[0.7 (electronic mini-spirometry) and FEV1/FVC B0.7 or [0.7 (standardized pulmonary function tests)
unaware of their respiratory disease prior to the study. The duration of foddering was significantly higher in FI-COPD patients, as this task exposed the farmers to high concentration of dust. The standardized pulmonary function test is the gold standard to diagnose bronchial obstruction. Portable pneumotachographs can be used in on-site settings, but they need to be calibrated daily for atmospheric pressure, hygrometry, and temperature (Chaudemanche et al. 2003; Dalphin et al. 1998a, b; Eduard et al. 2009; Gainet et al. 2007; Venier et al. 2006). Moreover, if farms are distant from one to another, then there is a need to calibrate the spirometer at each site, at least for temperature. The size and simplicity of the EMS device made it easy to screen for bronchial obstructions and could be a useful tool for occupational health physicians, especially in an on-site setting. In addition, an exhalation maneuver for 6 s was easier to accomplish in most patients. Thus, the results seemed to more reproducible and less prone to error compared with FVC (Kaufmann et al. 2009). EMS has been validated to screen patients for bronchial obstructions in primary care settings (Hankinson et al. 2003; Kaufmann
et al. 2009). FEV1/FEV6 can be used as a valid alternative for FEV1/FVC in diagnosing airway obstructions (Collectif Capital Souffle 2007; Jing et al. 2009; Lundgren et al. 2007). However, mild forms of airflow limitation can be missed because of possible underestimation when using a cutoff point of 0.7 for FEV1/FEV6 (Vandevoorde et al. 2006). We had chosen the high cutoff point of 0.8 for FEV1/FEV6 to be sure not to miss a single slight airflow limitation and thus, accepting a high rate of false-positive results, especially in a screening setting (Kaufmann et al. 2009). Indeed, we observe a good correlation between the two techniques (Fig. 2) and the differences between FEV1/ FEV6 and FEV1/FVC ratios are minor with a mean of 0.03. Comparing the EMS to the standardized lung function test, we observed only 5 false-positive subjects with FEV1/FEV6 B0.7 and FEV1/FVC [0.7. Both measurements are in accordance in 33/45 (Table 1). One limitation of the study design was that subjects with FEV1/FEV6 [0.8 were considered healthy and were not subject to standardized lung function tests. Therefore, we cannot assess the sensitivity and specificity of our EMS device. One of the strengths of our study was that all measurements with the EMS were performed by the same doctor, which increased reproducibility of our FEV1/FEV6 ratios. It would be of interest to assess this device with more physicians, including occupational health care specialists in larger populations. The population of farmers did not complain of any symptoms nor did they consult their medical doctors until very advanced stages of the disease despite suffering from cough, chronic bronchitis, or dyspnea. This poor perception of COPD symptoms has also been shown in the general
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Table 2 Characteristics and symptoms of 147 subjects with a comparison between farming-induced COPD (FI-COPD, n = 7) and nonobstructive (n = 133) subjects Farming-induced COPD (n = 7)
Non-obstructive subjects (n = 133)
Whole population (n = 147)
Age (years)
50.1 ± 9.1
48.3 ± 4.2
48.7 ± 8.6
Gender m/f (% m)
6/1 (86%)
77/56 (58%)
87/60 (59%)
Smoker (%)
0
13.5
15.0
Cough (%)
14.2
17.3
19.0
Chronic bronchitis (%)
14.2
11.3
12.9
Dyspnea (%)
71.4*
16.5*
21.7
There was significantly more dyspnea in the FI-COPD patients compared with the non-obstructive patients. Cough and chronic bronchitis were not different between the groups. The subjects were considered as ‘‘smokers’’ if they had a smoking history [5 pack-year * P = 0.004 (farming-induced COPD vs. non-obstructive subjects; Fischer’s exact test)
population (Roche et al. 2009). It was interesting to notice that the 14 obstructive farmers diagnosed had a mean age of 50 years, which is relatively young compared with the older retired farmers we normally diagnose at our respiratory department. Indeed, in our experience, we commonly have diagnosed COPD in farmers when they are at terminal stage of their obstructive disease with frequent exacerbations and often need oxygen supplementation. Diagnosing COPD at an earlier GOLD stage allows us to manage the disease earlier, decrease the lung function decline, enhance quality of life, and decrease the number of exacerbations in smoking-induced COPD (Cazzola and Tashkin 2009; Decramer et al. 2009; Rennard et al. 2001; Tashkin et al. 2008). Therefore, to screen farmers for bronchial obstruction is relevant. Indeed, 4 of our obstructive patients were free of respiratory symptoms despite FEV1/ FVC B0.7 and underwent standardized pulmonary function tests solely on the FEV1/FEV6 ratio. Dyspnea was the main symptom in our study, with a prevalence of 71% in FI-COPD patients versus 16% in non-obstructive subjects. The prevalence of dyspnea in our dairy farmer population (21.7%) has been similar to other studies (18.5–28%) (Chaudemanche et al. 2003; Dalphin et al. 1998a, b; Mustajbegovic et al. 2001). The prevalence of chronic bronchitis (12.9%) has also been similar to other studies (5.8–17%) (Chaudemanche et al. 2003; Dalphin et al. 1998a, b; Eduard et al. 2009; Gainet et al. 2007). According to the literature, the prevalence of chronic bronchitis has been higher and respiratory function has been lower in dairy farmers compared with control groups (Chaudemanche et al. 2003; Dalphin et al. 1998a, b; Gainet et al. 2007). It has been interesting to notice that even in 2008, with most of the farms in our study being modern, approximately 10% of the farmer population was considered obstructive; however, it has been shown that the more modern the farm, the less decline in the lung function of farmers (Venier et al. 2006). Barn threshing and cattle foddering were incriminating tasks because of plant dust
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exposure inducing chronic bronchitis (Dalphin et al. 1993). Grain handlers and swine confinement workers were also at risk of chronic respiratory symptoms, especially in female workers (Senthilselvan et al. 2007; Zejda et al. 1993). These respiratory symptoms were linked to the number of hours worked per day, which was an indirect index of exposure. We used the same method to assess exposure to dust when measuring the duration of specific farming tasks, mainly milking, straw litter spreading, and foddering, as previously described (Zejda et al. 1993). The daily duration of foddering, which has been responsible for the majority of dust exposure, was significantly higher in the FI-COPD group compared with the non-obstructive group. None of the farmers were using filter masks during our screening study. Interestingly, after the study, some farmers were using them for foddering and straw litter spreading, and other farmers were doing these two tasks separately from milking, which was done by another farmer to avoid inhalation of dust. Further studies are needed to assess if using a filter mask for these activities will be beneficial in preventing bronchial obstruction, inflammation, and development of COPD. The pathophysiology of FI-COPD is unclear, but ammonia, hydrogen sulfide, inorganic and organic dust may be involved, although a role for specific biological agents cannot be excluded (Eduard et al. 2009). There has also been some evidence that pesticide use may increase the prevalence of chronic bronchitis (Hoppin et al. 2007). To improve understanding of the pathophysiology of FI-COPD, it would be of interest to compare measurements of volatile organic compounds, particulate air pollution, and endotoxins in dairy farms from both the obstructive patients and the ‘‘healthy’’ subjects collected in our study. The duration of tractor and biomass fuel usage (open fireplace at home or on the farm) was not different between obstructive and non-obstructive farmers. Biomass smoke exposition has been a well-known COPD determinant in countries with low to middle income (Mannino and Buist 2007). In our study in France, it was expected that fireplaces were not a risk factor for bronchial obstruction.
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physicians deserves to be considered. Also, on-site air quality assessment of farming activities would be of interest to better understand the mechanism of this disease. Acknowledgments The authors thank the farmers for their participation, Antoine Magnan, Philippe Delaval and Nadia Khorasani for their help in writing the manuscript and the ‘‘Mutualite´ Sociale Agricole des portes de Bretagne’’ for their help in accessing the database on farming activities. Conflict of interest
The authors declare no conflict of interest.
References
Fig. 3 Daily duration of foddering was significantly higher in farming-induced patients (FEV1/FVC B0.7) compared with nonobstructive subjects (FEV1/FVC [0.7) with 43 versus 17 min (P = 0.02; Fig. 3a). Daily duration of straw litter spreading was significantly higher in pooled asthmatics and smoking-induced patients compared with non-obstructive subjects (Fig. 3b). We observed no difference in the daily duration of milking (Fig. 3c). ‘‘Other obstructive’’ group (n = 7) consisted in pooled patients with asthma (n = 4) and smoking-induced COPD (n = 3), both with FEV1/FVC B0.7
Nevertheless, we were expecting more cast iron fireplace inserts and less open fireplaces in our population. In conclusion, the use of an EMS device was a convenient means of on-site screening for farming-induced COPD in this specific population of dairy farmers, who did not complain about respiratory symptoms until the disease was at an advanced stage. Foddering was considered to be a significant risk factor. Using a filter mask for this activity could be beneficial in preventing bronchial obstruction and therefore, the development of COPD in these farmers. A larger study is needed to confirm these results. Adding routine EMS devices to the armamentarium of occupational
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