Reference values for forced expiration parameters in Bulgarian children and adolescents aged 7 to 18 years.

INTRODUCTION: A diagnosis of lung function impairment in childhood is highly dependent on the respective reference values. Population differences in the pulmonary function of children have been frequently reported. The AIM of this study was to derive normal spirometric reference values for Bulgarian children and adolescents and to compare these results with other data set including our own reference equations developed 20 years ago. MATERIAL AND METHODS: Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and parameters of maximum expiratory flow-volume curves were measured in 671 healthy Bulgarian school children (339 males and 332 females) aged 7-18 years. Multiple linear regression analysis was performed for each spirometric parameter against age, height, weight, chest circumferences and fat free mass in both sexes. RESULTS: Excluding ratios, all measured spirometric parameters increased nonlinearly with age and height, and were significantly higher in boys than girls in adolescence. Height (H) explained the maximum variance for spirometric parameters and the best-fit regression equation relating functional parameters and body height was a power function (Y = a.Hb). FVC and FEV1 showed close correlations with height (r2 between 0.85 and 0.92), whereas the coefficients of determination for the flows were less close (r2 from 0.85 for PEF to 0.67 for MEF25%; always higher in boys). CONCLUSIONS: The developed prediction equations can be used in clinical practice. In comparison with reference equations based on European or USA populations, regional reference values are biologically more suitable for the interpretation of spirometric data.

Respiratory and cardiovascular functions among smoking and nonsmoking girls from two regions with different air pollution degree.

AIM: The aim of the present study was to analyze the respiratory and cardiovascular functions among smoking and nonsmoking girls attending two schools situated in regions with different levels of air pollution. The characteristic of air pollution is based on the data gathered by stations 1 and 2 belonging to the Uniform National System for Monitoring the Air Pollution in Bulgaria. The participants (n=108, 16.07+/-0.80 years) were separated in two groups: smokers (S1 - from school 1, S2 - from school 2) and nonsmokers (NS1 - from school 1, NS2 - from school 2). All of them performed pulmonary function testing and .cardiopulmonary exercise testing on a treadmill using our modification of the Balke protocol (Marinov et al., 2000). Reference values for European children, previously validated for the Bulgarian population, were used. RESULTS: There are no significant differences in mean levels of VC, IC, FEV1, MEF50 and MEF25 (as a percentage from the predicted value as well). The average level of the Tiffneau index is noticeably higher among nonsmokers from the two regions and is the lowest among smokers from the more polluted area, but a significant difference exists between S2 (88.7+/-5.9) and NS2 (92.6+/-4.7), p=0.047; T(L,CO)%pred: S1 (85.4+/-7.2) vs. S2 (86.7+/-8.2), p=0.048 and NS1 (88.3+/-8.2) vs. NS2 (92.8+/-14.5), p=0.037; V(E)%pred: S1 (127.5+/-9.6) vs. S2 (123.7+/-6.1), p=0.035; higher levels of total lung capacity (TLC%pred), S1 (107.3+/-9.2) vs. NS2 (104.3+/-9.1), p=0.009 and alveolar ventilation (VA), S1 (5.0+/-0.6) vs. NS2 (4.6+/-0.5), p=0.008. CONCLUSIONS: 1. The negative effects of the combined influence of tobacco smoking and air pollution on some respiratory and cardiovascular functions of adolescent girls are more pronounced than each influence alone. 2. The cardiopulmonary exercise test gives adequate information about the combined effect of air pollution and smoking and using it for preventive purposes is an advisable method.