Principles of Subglottic and Tracheal Visualization with Transnasal Flexible Laryngoscopy.

The subglottic area and trachea are important parts of the upper airway, and can be visualized easily using transnasal flexible laryngoscopy (TFL). The aim of this study was to develop a clinical grading system to assist in documentation of the subglottic area and trachea with TFL, and to demonstrate the basic principles of visualization of these anatomic areas as a laryngology practice. The TFL videos of 100 randomized patients were evaluated by three laryngologists. The simple head extension (SHE) position and flexion position (FP) were applied to the patients during the visualization of the subglottic area and trachea. A paired t test was used to compare the grades of the subglottic and tracheal view according to the SHE and FP scores. This study examined 50 male and 50 female patients ranging in age from 28 to 83 years (mean age: 50.09 ± 13.05 years). For the SHE and FP, the numbers of patients constituting grade 1 were 2 and 35, grade 2 were 2 and 37, grade 3 were 30 and 19, and grade 4 were 41 and 9, respectively. There was a statistically significant difference between SHE and FP (P  <  0.05). The k score was 0.785 between the ratings of observer 1 and observer 2; 0.771 between observer 1 and observer 3; and 0.757 between observer 2 and observer 3 (P  <  0.001). This new grading system for the visualization of the subglottis and trachea can help physicians assess and identify the upper airways, and FP provides a better subglottic and tracheal view than SHE.

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