Among healthy never-smokers, forced expiratory volume in one second (FEV1) and maximal voluntary ventilation (40 breaths per minute, MVV40) divided by total lung capacity (TLC) showed less interindividual variability than FEV1 and MVV40, whereas the interindividual variability of other flow variables increased after division by TLC. FEV1, MVV40 and peak expiratory flow (PEF) divided by TLC had higher Student's t-values than FEV1, MVV40 or PEF in comparisons between 224 smokers and 232 never-smokers or between 137 asthmatic patients and 456 reference subjects. Thus these airflow variables corrected for lung size appear to be generally useful indicators of airflow limitation. In these comparisons, the variables were adjusted for body size. All t-test comparisons were based on an equal number of tests. Forced expiratory flow at 70% of TLC (MEF70%TLC) and the area of the expiratory part of the flow-volume curve had the highest t-values when comparing airflow before and after bronchodilatation in 70 asthmatic subjects, except in subjects with more advanced bronchoconstriction in whom MVV40 ranked highest. For the computation of MEF70%TLC, measured TLC could be substituted with predicted TLC with little loss of discriminatory capacity. Reference equations for forced expiratory flow at different TLC fractions and for FEV1/TLC are given.

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Reference values for gas exchange during exercise in healthy nonsmoking and smoking men.

The gas exchange at rest and during exercise was measured in 50 healthy men, 25 lifelong nonsmokers and 25 smokers, between 20 and 65 years of age. Arterial blood samples were taken and expired air was collected at rest, supine and sitting, and during graded exercise. Prediction formulas for various gas exchange variables were obtained by multiple regression. Optimal conditions for gas transfer were present at light exercise. The arterial oxygen tension (PaO2) remained approximately constant during exercise, although in individual smokers and nonsmokers it decreased by up to 1.8 kPa (13.5 mmHg) between a workload of 50 W and the maximal workload. The lower limit for PaO2 at maximal exercise was about 10.7 kPa (80 mmHg). The alveolo-arterial difference in oxygen tension (PA-aO2) increased considerably with increased workload, from 1.09 +/- 1.05 kPa at 50 W to 3.1 +/- 0.9 kPa at maximal exercise. Ageing and tobacco smoking were associated with a decrease in PaO2 and an increase in PA-aO2 at rest in the supine position, but at maximal exercise neither PaO2 nor PA-aO2 was significantly influenced by age or tobacco smoking. In contrast, the dead space and total ventilation were increased during exercise by ageing and tobacco smoking.

Adult↗

PubMedDate not supplied

Reference values for lung function tests in females. Regression equations with smoking variables.

Prediction formulas for static and dynamic spirometry, gas distribution, static lung mechanics and transfer test were derived from measurements in healthy females. The measurements included total lung capacity, residual volume, airway resistance, static elastic recoil pressure of the lung, static compliance, closing volume, slope of the alveolar plateau (phase III), flow-volume variables (including mean transit time) during breathing of air or a helium/oxygen mixture, and conventional spirometric indices. The results from 86 smokers and 100 never-smokers were evaluated separately and combined. For all lung function tests, a single regression equation including time-related smoking variables, valid for both smokers and never-smokers, was obtained. For many lung function tests, a nonlinear age coefficient resulted in a significant reduction in variance compared with simple linear models. Heavy tobacco smoking influenced most lung function tests less than ageing from 20 to 70 years, but for airway resistance, volumic airway conductance, closing volume, phase III, FEV1/VC, volume of isoflow and mean transit time the opposite was found.

Adult↗