[Basic spirometry measurements in workers on pig farmers].

Abstract

INTRODUCTION: Many epidemiological and clinical studies have demonstrated an increased risk for the symptoms of respiratory disorders consistent with chronic bronchitis and asthma and alterations of pulmonary function tests in pig farmers. AIM: The aim of this study was to determine basic pulmonary function values in workers in swine confinement buildings and to compare them with the same values in the control group of unexposed persons. The next aim was to examine the association between these values with duration of professional exposure, cigarette smoking, age, and sex of the examined persons. METHODS: We randomly selected for examination 145 workers of both sex who had worked for at least 2 previous years in pig farms and spent at least 3 hours per day, 6 days per week in a swine confinement building. The farmers worked at 6 different farms with 12,383 pigs on average on each farms. The subject was eligible for the study if he had had no history of atopic disease nor any serious chronic disease, and no acute respiratory infection within 3 previous months. As control group we examined 156 subjects who had lived and/or worked in the same areas and had had no history of exposure to farming environment or any other known occupational air pollutants. In both groups the study comprised cigarette smokers and persons who had never smoked. Pulmonary function data were collected according to the standard protocol with a Micro Spirometer, (Micro Medical Ltd, England, UK). The registered parameters were FEV1 and FVC. At least three satisfactory forced maximal expirations were performed by each subject and the best value was accepted for analyses. The results were also expressed as a percentage of predicted values and FEV1/FVC x 100 was calculated. RESULTS: There were no differences in the main demographic characteristics between two examined groups (Table 1). Mean duration of work in pig farming was 11.6 years (SD=8.5; range 2-40). The average values of examined pulmonary function tests are shown in table 2. The values of FEV1 and FVC in each groups were between 92% and 97% of predicted values, and FEV1/FVC x 100 was not lower than 82%. There were no differences in the average values of FEV1 (p=0.574) and FEV1 % predicted (p=0.653) between pig farmers and control subjects. Pearson coefficient of correlation and Spearman nonparametric correlation test revealed a high level of correlation of FEV1 values with sex and age and no correlation of pig farming exposure with cigarette smoking as predictor variables (Table 3). The analysis by linear regression method showed that all examined predictor variables had the effect on the value of FEV1 (Table 4). After the elimination of the two least significant predictor variables it was possible to make the equation for prediction of FEV1 values. DISCUSSION: In the present study there are no significant alterations in the values of the basic pulmonary function tests in pig farmers. In the majority of previous similar studies the differences in the average values of FEV1 and FVC between pig farmers and control subjects were also not found. However, in some studies the alterations in several more specific lung function parameters were registered. The decreased values of FEV1 during workshift were also found and they are probably connected to the bronchial hyperreactivity registered in many studies in pig farmers. Longer exposure to swine confinement environment caused more decline in FEV1 and FVC and accelerated mean age-related annual decline in FEV1 was observed reaching to 44 ml/yrs more than expected. The correlations between values of FEV1 with pig farming exposure and cigarette smoking in this study were not found. However, the analysis by linear regression method showed that all examined predictor variables had the effect on the value of FEV1. In a few previous bronchoscopic, BAL and sputum studies some signs of inflammation and morphological changes of the respiratory tract were observed. The absence of important alterations in the basic spirometric measures in this and the majority of the previous studies suggests that early airway injuries may not be readily apparent using spirometric measures of lung function. CONCLUSION: In contrast to other world studies, our study comprised an important number of women farmers, but alterations associated to sex were not found. To assess the lung function in these pig farmers after several years may be of great importance.