[Lung function in the elderly: do we need new reference values?]

The structure of our aging population has significantly changed in the last three decades as have also the anthropometric data. Therefore, the question arises as to whether or not the largely accepted reference values for ventilatory lung function, which were suggested by the European Community for Coal and Steel (EGKS), may still be used today, since these values were obtained in the 1960s from subjects in a limited age range. For the elderly, the measured values are deduced by extrapolation beyond the range of reference equations which had been obtained in a different population. Therefore decisions concerning elderly and smaller subjects concerning remuneration due to impaired lung function after industrial exposure on the basis of EGKS values are questionable.

We have examined lung function using pneumotachography for recording static lung volumes and flow-volume curves in 176 asymptomatic non-smoking males, aged 20 to 90 years, and correlated the results to the reference values of the EGKS, SAPALDIA and LuftiBus.

The age dependence of respiratory parameters (VC, FVC, FEV (1), FEV (1) %FVC, PEF, MEF (75,50,25)) for the healthy subjects can be described with a linear function (y = - m x age + n). The forced expiratory volume in one second, FEV (1), is calculated by FEV (1) = - 0.046 x age + 6.11; r = 0.88. Mean FEV1 for younger subjects was found to be 108 +/- 9.9 % of the EGKS reference values, 105 +/- 13.7 % in the middle-aged group and 97.3 +/- 12.4 % in the older subjects. All measured parameters concerning lung function can be described as linear functions of age which are steeper than those described by the EGKS reference values. The steeper slope in age dependency was also seen in other investigated parameters. The correlation of lung function parameters to height largely follows the EGKS predictions.

Measured lung function values of healthy younger and elderly subjects showed a close correlation to the extrapolated reference values of the EGKS. Our results relating to normal lung function justify an extrapolation of the reference equations beyond the common ranges of age while applying the same limitations as described for subjects in the middle-age range. Our results permit an extrapolation of EGKS values beyond the range of the reference values and can be used for the classification of impaired lung function in older subjects. The alternatively discussed reference equations of the SALPADIA Study, of NHANES and partially of the LuftiBus Study are higher, but do not cover all the necessary parameters and/or age ranges. A multicentric study for contemporary reference values should be performed in order to solve the problems concerning valid reference values.