Flow-Volume Curve Analysis for Predicting Recurrence After Endoscopic Dilation of Airway Stenosis.

BACKGROUND: The flow-volume curve is a simple test for diagnosing upper airway obstruction. We evaluated its use to predict recurrence in patients undergoing endoscopic dilation for treatment of benign upper airway stenosis. METHODS: The data of 89 consecutive patients undergoing endoscopic dilation of simple upper airway stenosis were retrospectively reviewed. Morphologic distortion of flow-volume loop (visual analysis) and quantitative criteria, including maximal expiratory flow rate at 50% of the vital capacity (MEF50%)/maximal inspiratory flow rate at 50% of the vital capacity (MIF50%) of less than 0.3 or more than 1.0, forced expiratory volume in 1 second/MEF exceeding 10, and forced expiratory volume in 1 second/forced expiratory volume in .05 second exceeding 1.5, were considered predictive of recurrence. In all cases, the recurrence was confirmed by radiologic or bronchoscopic findings, or both. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of visual, quantitative, and aggregate criteria for detecting recurrence were computed and compared. RESULTS: Of 89 patients treated, 27 (30%) had a recurrence. Visual analysis presented a sensitivity, specificity, PPV, NPV, and accuracy of 63%, 83.9%, 63%, 83.9%, and 77.5%, respectively. Among the quantitative criterion, the MEF50%/MIF50% was the most accurate, having a sensitivity, specificity, PPV, NPV, and accuracy of 77.8%, 79%, 61.8%, and 89.1%, and 78.7%, respectively. Aggregate criterion presented the best yield compared with other criteria in sensitivity (81.5%), specificity (91.9%), PPV (81.5%), NPV (91.9%), and accuracy (88.8%). CONCLUSIONS: The flow-volume curve is a simple and noninvasive method to monitor patients undergoing endoscopic dilation of upper airway stenosis. Morphologic changes in the flow-volume loop and in the MEF50%/MIF50% ratio are suggestive of recurrence and guide the physician to implement the follow-up with further diagnostic (non)invasive examinations.