Interpretation of changes in spirographic and flow-volume variables after operative treatment in bilateral vocal cord paralysis.

In 13 patients, who underwent a superolateralization of a vocal cord after bilateral vocal cord paralysis, we studied pre- and postoperatively spirometric dynamic and static lung volumes and variables from maximal expiratory and maximal inspiratory flow-volume (MEFV and MIFV) curves. The effects of surgical treatment on these variables have been established by comparing the statistical significance of the changes post- versus preoperative. A significant increase was found in the vital capacity and a significant decrease in the indices associated with the dynamic variability of the obstruction. The most significant changes were found in peak inspiratory flow and peak expiratory flow, and in the inspiratory defined dynamic estimates, as forced inspiratory volume in 1 second and maximal voluntary ventilation at a frequency of 30 c X min-1. Significant correlations, however, were found to exist only for the changes within the group of flow-volume indices and for those within the group of spirographic variables. This led us to the conclusion that for the diagnosis of this type of upper airway obstruction these measurements are additive, reflecting different aspects of airway mechanics.