A five-year followup of lung function among chemical workers using flow volume and impedance measurements

Impedance of the respiratory system, measured using the forced oscillation technique (FOT), has repeatedly been proposed as a tool for occupational health screening. The aim of this study was to compare the outcome of impedance measurements and flow-volume curves, and to study relationships between lung function decline and specific exposures and smoking. Both measurements were applied in 136 chemical workers from seven main production/personnel groups during a 5 year follow-up (1990-1995). The prevalence of airway obstruction (forced expiratory volume in one second (FEV1) 330 mL) was only accompanied by a significant decrease in the reactance at 8 Hz (X8) and an increase in the resonance frequency (f0). Interestingly, decline in FEV1 was significantly dependent on age, years of employment, pack-years, FEV1, and all impedance parameters at the start in 1990 (r=0.35; p=0.01). Similarly, the increase in f0 was significantly dependent on age, years of employment, pack-years, f0, FEV1, forced vital capacity (FVC), peak expiratory flow (PEF) and maximal mid-expiratory flow (MMEF) at the start (r=0.56;