Evaluation of physiological tests in epidemiological surveys of lung function. Final report on CEC Contract 6244-00-8-102

A comparison has been made of the correlation between the cumulative dust exposure of coalminers and various tests of pulmonary function. In particular it was intended to assess the usefulness of tests of small airways function (SAP) in the investigation of occupational lung disease. It is uncertain whether more complex tests of SAP performed on a limited sample of coal-workers will provide more information than one or two simple measurements made on the entire population.Results are reported of lung function tests carried out on 943 underground workers drawn from groups of (1) young men, who have just begun work at the coal face; (2) older men, who have had their dust exposure monitored since starting work at the face 20 years ago; (3) men with simple pneumoconiosis (CWP); (4) men without CWP of the same age range as (3) and (5) men without GOT selected randomly from the remainder of the population.Measurements included were lung volumes by spirometry and helium dilution, carbon monoxide transfer factor during breathholding and steady state exercise, one second forced expiratory volume, maximum expiratory flow at 50/o and 25%of vital capacity… (Vmax50 and Vmax25), volume of isoflow breathing helium (V .isoV), single breath nitrogen index of uneven distribution of ventilation and closing volume.A statistical analysis of the correlation of 16 selected measurements of lung function (LF) with dust exposure enabled partial correlation coefficients to be derived for each variable. Allowance was made for the contributory effects of CWP, smoking habits and the presence of symptoms of bronchitis and breath-lessness amongst other factors, which may have accounted for the variability of each LP variable.Deterioration in several measurements was significantly related to dust exposure, although the absolute effect was relatively small. The one second forced expiratory volume : forced vital capacity ratio was most closely correlated withdust exposure (partial correlation : P<0.01), while N2 index and Vmax50, (P<0.05), one second forced expiratory volume, residual volume and forced expired time (P<0.10) also showed some correlation with dust exposure.It is concluded that, within the limitations of the present analysis, FEV. and FEV../FVC, which are measurable by simple spirometry, provide as much information about the effects of airborne dust exposure as d'o technically more complex SAP tests, such as instantaneous maximum expiratory flow rates. V isoV and closing volume (expressed as closing capacity as a percentage of total lung capacity) demonstrated no correlation with dust exposure and therefore do not appear to warrant inclusion in a cross-sectional, epidemiological survey of this kind.Measurements of forced expiration could justifiably be included in surveys of occupational effects of dust exposure. It is noted that an improved 'best fit' model relating LP to its explanatory variables needs to be achieved in order to decrease the proportion of unexplained variability of some of the physiological measurements. However, there is evidence in the literature that tests of SAF, which generally have poorer reproducibility than FEV>, may be more useful in studying the course of occupational lung disease in longitudinal or follow-up studies of workers in dusty locations. “”