Applying the ‘expiratory disproportion index’ in the pulmonary clinic as a spirometry-derived screening tool for upper airway obstruction in adults

Upper airway obstructions, such as a subglottic stenosis, are often not recognized early due to the asthma-like symptoms. This delay may result in a high morbidity and mortality. In this study, our aim was to evaluate the clinical implementation of the expiratory disproportion index (EDI), derived from standard spirometry, as a non-invasive screening method for upper airway obstructions in new patients in the outpatient pulmonary clinic. In a retrospective cohort study, we analysed the EDI and the subsequent clinical course of 244 consecutive patients referred for spirometry. Of 244 patients, 3 patients with an upper airway obstruction were identified by EDI and confirmed with endoscopy. This study supports the use of the EDI as a standard screening tool for earlier detection of UAO, representing a simple and effective approach with limited impact on the number of referrals generated. Therefore, this study strengthens the validation of the EDI parameter as non-invasive screening tool for patients with upper airway obstructions presenting in the outpatient pulmonary clinic.