Objective Sizing of Upper Airway Stenosis: A Quantitative Endoscopic Approach

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Abstract
In patients with airway stenosis, anatomy of the lesion determines the magnitude of the biomechanical ventilatory disturbance and thus the nature and severity of symptoms. It also gives information about biology, likelihood of response to treatment, and prognosis of laryngotracheal lesions. Accurate airway sizing throughout treatment is therefore central to managing this condition. We developed a method for objective assessment of airway lesions during endoscopy. We used airway simulations to investigate the effects of endoscope tilt and lens distortions on measurement accuracy, devising and validating clinical rules for quantitative airway endoscopy. A calibrator was designed to assess lesion length, location, and cross-section during tracheoscopy. It proved possible to calculate the length and location of the stenosis using simple mathematics. Cross-section measurements were more than 95% accurate, independent of endoscope tilt and without making assumptions about endoscope optics and visuospatial distortion, for both pediatric and adult airway dimensions. The technique was used to characterize airway lesions in 10 adult patients with an average age of 48 years undergoing therapeutic laryngotracheoscopy. Lesions occurred on average 36 mm below the glottis (range, 21-54 mm) and were 9.3 mm long (5-17 mm). The average pretreatment airway cross-section was 48.3 mm, increasing to 141.1 mm after laser therapy. Two independent observers calculated airway cross-sections, achieving an interobserver concordance of 0.98. This method can be used to objectively and precisely determine the anatomy of airway lesions, allowing accurate documentation of lesion characteristics and surgical results, serial monitoring throughout treatment, and comparison of outcomes between different centers.

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