Normal values for the ratio of one-second forced expiratory volume to forced vital capacity.

Abstract

Normal standards for the ratio of 1-second forced expiratory volume to forced vital capacity have previously either assumed a value greater than 70 or 75 per cent or else provided prediction formulas based on populations of small size or groups that included cigarette smokers. The ratio was measured in 963 healthy, nonsmoking men and women. Negative correlation was obtained with age, and no significant correlation was found with standing height. Regression equations were derived for men and women. The addition of standing height did not affect the multiple correlation coefficient and standard error of the estimate for women but did have a small influence for men. Normal mean values and standard deviations by age decade were tabulated. With these more precise values, differentiation between restrictive and obstructive abnormalities is improved. The relative contribution of each process to impairment of ventilation is revealed by the relationship of the forced vital capacity and the ratio of 1-second forced...