The MVV/FEV1 ratio in normal and asthmatic subjects.

We compared the ratio of maximal voluntary ventilation/forced expiratory volume in one second (MVV/FEV1) in normal individuals and asthmatic subjects. Our hypothesis was that MVV/FEV1 would be lower in asthmatic subjects. We also compared MVV/FEV1 results with the effects of deep inspiration (DI) on bronchomotor tone and with methacholine responsiveness. In normal subjects, MVV/FEV1 was higher than that in asthmatic subjects. Specific conductance (SGaw) increased after a single DI or an MVV maneuver in normal individuals. An MVV maneuver caused SGaw to decrease in asthmatic subjects. In asthmatic subjects, there was a significant correlation between MVV/FEV1 ratio and magnitude of decrease in SGaw after an MVV maneuver. Results of methacholine testing indicated that asthmatic subjects with low MVV/FEV1 ratios were more responsive to methacholine than those whose MVV/FEV1 ratios were within normal range. We conclude that MVV/FEV1 ratios are abnormally low in many asthmatic subjects and that low MVV/FEV1 ratios may indicate increased bronchial responsiveness to methacholine.