Short-term ventilatory effects in workers exposed to fumes containing zinc oxide: comparison of forced oscillation technique with spirometry.

Following the occurrence of metal fume fever in some subjects after the installation of an electric furnace in a steel plant, a survey was undertaken to examine whether subjects exposed to fumes containing zinc oxide would exhibit a detectable impairment in ventilatory function, and whether a forced oscillation technique (FOT) was more suited for this detection than conventional spirometry. Pulmonary function measurements were made in 57 exposed workers (production or maintenance) and 55 nonexposed workers (maintenance or strandcasting department) at the beginning and near the end of a work shift (day or night). Maximal expiratory volumes and flows were measured by means of a pneumotachograph, and respiratory resistance (Rrs) and reactance at various frequencies by means of a FOT. These measurements were repeated 1 day later. During the day shift, there were no significant differences in pulmonary function between exposed and control workers. However, during the night shift, an influence of exposure on pulmonary function was revealed both by spirometry and by FOT: workers exposed at night showed a slight decrease in vital capacity (VC) and in forced expiratory volume in one second (FEV1), and a decline in respiratory resistance (Rrs) with oscillation frequency, that were more marked than in unexposed subjects. In contrast to the frequency dependence of Rrs, the changes of lung volumes and expiratory flows were related to differences in initial values between exposed and nonexposed workers. The decrease in FEV1 was maintained the day after exposure. The forced oscillation technique proved at least as sensitive as spirometry to detect small across-shift changes in ventilatory function. Although the effects on pulmonary function were small, it is likely that they represent a subclinical response to the inhalation of small quantities of zinc oxide.

Total respiratory impedance measured by means of the forced oscillation technique in subjects with and without respiratory complaints.

The purpose of this study was to determine whether the forced oscillation technique is more sensitive than spirometry to detect lung function alterations in subjects with respiratory complaints. The input impedance of the respiratory system (between 2 and 24 Hz) and maximal expiratory flows and volumes were measured in 1,255 subjects referred for routine spirometry. A questionnaire concerning respiratory complaints was administered. A discriminant analysis was performed between subgroups of subjects without (137 males and 140 females), with moderate (115 males and 109 females) and with marked respiratory complaints (149 males and 132 females). A clear-cut separation was achieved by this analysis only between those subjects without and with marked complaints. Both lung volumes and flows as well as impedance parameters (mean value and frequency dependence of resistance in females, mean resistance in males) contributed to the discrimination of subjects without and with marked respiratory complaints, although there was only a moderate decrease of discriminative power when the impedance parameters were excluded. The contribution of the forced oscillation parameters to discriminative power was larger in females than in males (40 vs 19%), which may be related to the higher prevalence of asthma in our population of females. Excluding the subjects with marked functional impairment improved the share of forced oscillation parameters only slightly with respect to lung volumes and flows (females 54 vs males 23%). Considered separately, however, the sensitivity of spirometry and forced oscillation technique to detect symptomatic people appeared to be similar. We conclude that impedance measurements by forced oscillation technique and routine spirometry are both associated with respiratory complaints. Our results indicate that the information provided by impedance measurements can be complimentary to that obtained by spirometric indices.