Usefulness of a newly developed endoscope for the observation of the posterior tracheal wall

OBJECTIVE: Videoendoscopic evaluation of swallowing is an objective swallowing function evaluation method used in dysphagia rehabilitation. However, it is anatomically difficult to detect the entry of foreign substances through the posterior tracheal wall using a conventional endoscope (CE). In this study, we developed an endoscope that can observe the posterior tracheal wall and investigated its reliability and validity in healthy adults. METHODS: Twenty healthy adults were included. The trachea was observed from inside the larynx using a CE and a portable, flexible two‐step angulation endoscope (two‐AE) with a two‐step curved shaft tip. The visibility of the anterior and posterior walls was recorded. The time from the endoscope tip entering the larynx to the posterior tracheal wall was measured. Additionally, discomfort events were assessed after the examination. McNemar's test and a paired t‐test were used for statistical analysis. Kappa coefficients and concordance rates were calculated. RESULTS: The anterior tracheal wall was observed using both endoscopes. The posterior tracheal wall was significantly observed in 18 participants with the two‐AE (p < .001), compared to only three of 20 participants with the CE. The time to observation of the posterior tracheal wall for examiners 1 and 2 was 13.3 ± 6.5 and 12.0 ± 6.7 s, respectively, with no difference between groups (p = .400). The kappa coefficients of examiners 1 and 2 and between the examiners were 0.444, 0.643, and 0.643, respectively, with concordance rates of 90%, 95%, and 95%, respectively. CONCLUSION: Regardless of the examiner's years of experience, we observed that the two‐AE could observe the posterior tracheal wall. LEVEL OF EVIDENCE: Step 5.