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. Morphological distortion of flow-volume loop (visual analysis) and quantitative criteria including MEF50% /MIF50% <0.3 or > 1.0; FEV1 /MEF>10; and FEV1 /FEV0.5 >1.5 were considered as predictive of recurrence. In all cases, the recurrence was confirmed by radiological and/or bronchoscopic findings. The sensitivity, specificity, PPV, NPV, and accuracy of visual, quantitative and aggregate criteria for detecting recurrence were computed and compared.

RESULTS: Of89 patients treated, 27 (30%) had a recurrence. Visual analysis presented a sensitivity, specificity, PPV, NPV, and accuracy of 63%; 83.9%; 63%; and 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 to other criteria in terms of 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 non-invasive method to follow patients undergoing endoscopic dilation of upper airway stenosis. Morphological 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 exams.