Maximal expiratory and inspiratory flow-volume curves in bilateral vocal-cord paralysis. Changes after surgical treatment and comparison with glottic resistance characteristics.

The maximal expiratory flow-volume (MEFV) and maximal inspiratory flow-volume (MIFV) curve present maximal attainable flows, plotted against the displaced volume at the mouth during a forced expiratory manoeuvre from total lung capacity (TLC) and a subsequent forced inspiratory manoeuvre from residual volume (RV), respectively. Depending on the glottic resistance characteristics, the usual flow limitation may be absent during forced expiration, drastically influencing the form of MEFV curves. During forced inspiration however, the flow remains effort-dependent. We tested this hypothesis by comparing the form of MEFV and MIFV curves, and the glottic resistance characteristics, before and after an endolaryngeal superolateralization of a vocal cord, in 12 patients with bilateral vocal-cord paralysis. Peak expiratory and inspiratory flows were estimated with the aid of the measured glottic resistance characteristics on the assumption that the maximal alveolar pressures were normal during the manoeuvres. The estimated values agreed well with measured values. The form of the MEFV and MIFV curves was also found to be closely linked to the glottic resistance characteristics. It is concluded that the MEFV and MIFV curves are sensitive indicators of flow limitation in patients with upper-airway obstructions.