BRONCHODILATATION AND THE INSPIRATORY FLOW-VOLUME CURVE

The inspirator, flow volume curve is included in the spirometric traci ng provided by most pulmonary function laboratories and is useful in a ssessing upper airway abnormalities. We analyzed the changes in peak i nspiratory flow (PIF), forced inspiratory flow at 50% (FIF50), and for ced inspiratory vital capacity (FIVC) that occur with bronchodilator c hallenge resting (3 puffs of a beta-agonist by metered-dose inhaler wi thout a spacer device) in 145 consecutive patients, Fifty-five patient s responded to bronchodilators with either a 12% or 200-mL change in F EV(1) or FVC, All of these subjects produced forced expiratory maneuve rs that fulfilled American Thoracic Society criteria or acceptability. The FIVC was the only inspiratory parameter that consistently showed a similar correlation to the bronchodilator responsiveness demonstrate d by the FEV(1) or FVC. With the reduction in air trapping, a 12% or 2 00-mL change in the FIVC is additional confirmatory evidence of bronch odilator responsiveness.