Brit. oT. Dis. Chest (1966) 60, x97.

THE FORCED EXPIRATORY VOLUME AND THE PEAK EXPIRATORY FLOW RATE

IN PNEUMOCONIOSIS BY TREVOR PHILLIPS

Pneumoconiosis Medical Panel, Government Buildings, St. Mary's Place, Newcastle upon Tyne I

THE ventilatory function of subjects claiming disablement benefit for pneumo- coniosis is usually estimated by Pneumoconiosis Panels in this country by spirometry. The Wright Peak Flow Meter (Wright and McKerrow, 1959) is also often employed. Knowledge of the correlation between the forced ex- piratory volume (F.E.V.1) and the peak expiratory flow rate (P.E.F.R.) in pneumoconiosis would be valuable.

Materials and Method One hundred and sixty men with coal-miner's pneumoconiosis, who were

judged to be fully co-operative, were studied. In order to observe only those men who gave consistent results, no case was included where, excluding trial attempts, the difference between the highest and the lowest F.E.V. 1 was greater than 0"2 litres. The F.E.V. 1 was obtained with a Poulton spirometer with an electric timing device. The average P.E.F.R. was chosen in preference to the highest P.E.F.R. (Wright and McKerrow, I959) , and was plotted against the average F.E.V. 1. The first i io men were selected at random, and it was found that, of these, 27 (24 per cent.) had chronic bronchitis as defined by agreement among the Pneumoconiosis Panels, i.e. had suffered from rhonchi as well as a history of persistent cough and sputum for some part of the day for at least three months of the year, together with one or more chest illnesses causing absence from work for over a week, in the preceding three years. It was then noticed that the performance of the tests by the men with chronic bronchitis differed from that of those without chronic bronchitis. I t was therefore decided to divide the men into two groups, according to the presence or absence of chronic bronchitis. The remaining men were selected so as to bring the total number studied to I oo without chronic bronchitis and 60 with chronic bronch- itis.

Resul t s Group I : Pneumoconiosis without chronic bronchitis. The correlation coefficient

(r) was o'9394 , and the regression of F.E.V. 1 (y) on P.E.F.R. (x) was y = o.oo6289x, the estimated maximum possible error being o.7864. It was also found that the presence or absence of progressive massive fibrosis made no difference to this relationship.

(Recdved for publication, May r966 )

198 PHILLIPS

Group H: Pneumoconiosis with chronic bronchitis. The correlation coefficient here was o.8668, and the regression of F.E.V. 1 (y) on P.E.F.R. (x) was y=o.oo576x+o.3o16 , the estimated maximum possible error being o.7221. Here again, the presence or absence of progressive massive fibrosis made no difference to this relationship.

D i s c u s s i o n

A good correlation between the F.E.V. 1 and P.E.F.R. has been obtained in the past by many workers, though such a relation has not been shown in subjects with coal-miner's pneumoconiosis. Higgins (1957) found a correlation coefficient of 0.86 between the P.E.F.R. and the maximum breathing capacity in a random sample of elderly men who had never worked in dusty occupa- tions, while Shepherd (1962) obtained a correlation coefficient of 0"88 in his series of males with airways obstruction. Fairbairn et al. (I962) found that the correlation coefficient between F.E.V. 1 and P.E.F.R. was 0.8 in their series of 72 male Post Office employees, of whom 17 had chronic bronchitis. They also calculated that the regression of F.E.V. 1 (y) on P.E.F.R. (x) wasy=o.oo412x + 0-622, and suggested that the F.E.V. 1 in ml. could be roughly calculated by multiplying the P.E.F.R. by 4 and adding 600. A better correlation (r= 0.94 ) was obtained by Lal, Ferguson, and Campbell (1964) in 95 subjects, of whom about half were normal and half had diffuse airways obstruction: the regression obtained wasy = o.oo567x + 0"219. The only series where subjects with pneumo- coniosis were studied would appear to be that of Lockhart et al. (196o), who found that, while the correlation between the F.E.V. 1 and the P.E.F.R. was good in subjects with chronic bronchitis, asthma, and emphysema, it was poor in 16 flax-workers with byssinosis.

The present results show that a good correlation exists between the F.E.V. 1 and the P.E.F.R. in subjects with coal-miner's pneumoconiosis, even though the relationship varies if chronic bronchitis is present. This is to be expected, as the pattern of forced expiration in those subjects with chronic bronchitis differs from the normal. I t is therefore possible that the difference in correlation coefficients and regression equations obtained by previous workers has been due to the inclusion of a varying proportion of bronchitics in the groups observed. In this connection, it is noteworthy that the curve obtained by Lal and his colleagues from their subjects (half of whom had chronic bronchitis) falls approximately halfway between those obtained from the two groups in the present study.

The results also indicate that the F.E.V. 1 in coal miners with pneumo- coniosis but without chronic bronchitis may be calculated by multiplying the P.E.F.R. by 6.25. However, multiplying the P.E.F.R. by 6 is an easier mental calculation for everyday use, and the results should be sufficiently accurate for practical purposes. As for those miners with chronic bronchitis, the F.E.V. 1 in ml. may be conveniently estimated by multiplying the P.E.F.R. by 6 and adding 300.

T H E 1LE.V. 1 AND T H E P . E . F . R . IN PNEUMOCONIOSIS I99

Summary One hundred and sixty men with coal-miner's pneumoconiosis were studied

in two groups to ascertain whether a good correlation existed between the F.E.V. 1 and the P.E.F.R. The first group consisted of Ioo miners without chronic bronchitis and the second of 6o miners with chronic bronchitis.

Correlation was good in both groups. The results indicated that, if chronic bronchitis is absent, the F.E.V.1 in ml. may be estimated by multiplying the P.E.F.R. by 6-25, or, more conveniently, by 6. I f chronic bronchitis is present, the F.E.V. 1 in ml. may be obtained by multiplying the P.E.F.R. by 6 and adding 3oo.

It was also found that the presence of progressive massive fibrosis did not alter these relationships.

REFERENCES FAIRBAIRN, A. S., FLETCHER, C. M., TINKER, C. M., & WOOD, C. H. (I962). Thorax, x7, x68. HIOGINS, I. T. T. (I957). Brit. med. J., ii, xi98. LAL, S., FERGUSON, A. D., & CAMPBELL, E.J.M. (I964). Brit. med. J., ii, 814. LOCKnART, W., SMITH, D. H., MAre, A., & WILSON, W. A. (I96o). Brit. med. o7, ii, 37. SnnPnnRD, R.J. (I962). Thorax, x7, 39. WPaom', B. M., & McK~RROW, C. B. (I959). Brit. med..7., ii, io4I.