Inducible laryngeal obstruction: Endoscopic quantitative analysis of glottic aperture
Paulo Henrique Peitl Gregorio MD  Juliana Teixeira Gomes MBBS  Roberto Rodrigues MD, PhD  Marcia Jacomelli MD, PhD  Ellen Samara Santos MBBS  Marcelo Gervilla Gregorio MD, PhD
First published: 30 July 2019 https://doi.org/10.1002/lary.28213
The authors have no funding or conflicts of interest to disclose.
We thank our colleagues from Respsono Clinic who assisted the research throughout the entire process of development along 3 years. The authors would like to thank Rodrigo Edelmuth, MD, for his thorough review of the article.
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Abstract
Objectives
Using a method developed for this study, the objective was to perform a quantitative analysis of glottic aperture during the respiratory cycle in subjects suspected of having inducible laryngeal obstruction (ILO) and to compare results to healthy individuals. Correlations between glottic aperture and spirometric parameters were assessed.

Methods
Subjects with high clinical suspicion of ILO and atypical inspiratory findings in spirometry had the images of their laryngoscopy displayed alongside a respiratory flow chart and both were recorded simultaneously. This method allowed detailed analysis of the glottic aperture by measuring the angle of the anterior commissure during inspiration and expiration. Healthy volunteers who performed the same tests and agreed to provide data to this study were used as a control group.

Results
All 15 subjects with ILO and 16 healthy participants were evaluated successfully using the proposed method. Measures of the anterior commissure angle in the ILO versus control group were significantly different in all observed parameters and just three ILO subjects had an anterior commissure closure greater than 50% during the respiratory cycle. Inspired volume (FIF50) and mid‐vital capacity ratio (FEF50/FIF50) had a significant correlation with glottic aperture parameters when considering the evaluation of the subjects all together.

Conclusion
The proposed method provided precise and quantitative analysis of glottic aperture during the respiratory cycle thus indicating that the usage of equipment that allows for such assessment should be encouraged. Also, the threshold of vocal cords closure accepted as indicative of ILO should be reconsidered, especially during the intercritical period of the disease.

Level of Evidence
4 Laryngoscope, 2019