1006 workers occupationally exposed to such gases as chlorine, ammonia, phosgen and sulphur dioxide were investigated. Concentration of the substances were slightly higher (in 2-2,5 times) than their maximum allowable concentrations (MACs). Control group is consisted of 170 workers have never exposed to industrial pollutants.

Every worker has filled a questionaire included questions about presence, duration and character of cough; smoking habit. Chronic bronchitis was diagnosed in conformity with WHO recommendations [1]. Respiratory function investigation consisted of common tests: forced vital capacity (FVC), forced expiratory volume per 1 sec. (FEV1) Tiffenau index (FEV1/FVC), forced expiratory flow 25%, 50%, 75%, 25-75% (FEF₂₅, FEF_50, FEF₇₅, FEF_25-75), expressed in percentage to due values of standard in Russia [2].

Acid-base status of blood and gases in blood and expiratory air were investigated in 63 workers.

All data were treated by statistical methods. Original statistical programs were elaborated by Nizhny Novgorod Scientific Research Institute of Applied Mathematics and Cybernetics.

Questionaire results provide evidence that 252 of exposed workers (25.1%) have CB symptoms by epidemiological criteria. CB symptoms were revealed among 22 persons (14.9%) in control group. There were not significant differences in prevalence of CB among workers exposed to different gases. Results of CB prevalence investigation were confirmed by functional condition bronchopulmonary system analysis. It was established that all the gases equally adversely affected on bronchomotor function.

How to evaluate disturbances of bronchomotor function found in workers not having CB symptoms and mainly what is a role of the disturbances in CB developing? The prospective study was conducted to solve the problems.

Studies conducted after 2 years shown that among 89 workers occupationally exposed to irritant gases and who had only bronchial obstruction by previous study, CB symptoms were revealed in 10 persons (11.2%). Among 241 workers who did not have bronchial obstruction by previous study, CB symptoms were revealed in 12 persons (4.9%).

We have found close correlation between contents of oxygen in alveolar air and arterial blood and bronchomotor function indexes, especially FEF₅₀ and FEF₇₅.

Decreasing of FEF₅₀ and FEF₇₅ should be considered as adverse factor promoting CB development. It was confirmed by tendency to more frequent CB development in workers with bronchomotor function disturbances (revealed by primary examination) at level of small and middle bronchi.

The data are a prerequisite for formal procedure of issue solution about possible presence or high risk of CB development in workers. The procedure is based on respiratory function indexes detection. For that purpose preliminary discriminant analysis for each parameter was conducted. It allows to established that FEV₁/FVC, FEF₅₀, FEF₇₅, FEF_25-75 possess acceptable discrimination relatively CB. The highest informativeness of combination FEV₁/FVC, FEF₅₀, FEF₇₅ providing maximal degree of discrimination was revealed by correlation analysis of parameters with sufficient degree of discrimination.

Decision function was made up on basis of final discriminant analysis results:

f = 0,0271 · FEV₁/FVC + 0,016 · FEF₂₅ + 0,0173 · FEF₇₅ - 4,2614

Persons who have f <=0 should be considered as persons with preclinical symptoms of obstructive bronchitis (high risk of its development).

Thus, combined using of the questionaire and proposed algorithm enlarges possibilities of COB early diagnosis.

1. MSR Committee on etiology of chronic bronchitis. // Lancet.- 1965; (1):775-89

2. Klement RF, Aganezova ES, Kotegov IuM.Contemporary problems of clinical physiology of respiration Leningrad (1987). pp. 20-27.