Stereo Laryngoscopic Impact Site Prediction for Droplet-Based Stimulation of the Laryngeal Adductor Reflex

Jacob F Fast,Hardik R Dava,Maurice Krauth,Martin Ptok,Svenja Spindeldreier,Dennis Kundrat,Max-Heinrich Laves,Luder A Kahrs,Adrian K Ruppel

doi:10.1109/access.2021.3103049

Abstract

The laryngeal adductor reflex (LAR) is a vital reflex of the human larynx. LAR malfunctions may cause life-threatening aspiration events. An objective, noninvasive, and reproducible method for LAR assessment is still lacking. Stimulation of the larynx by droplet impact, termed Microdroplet Impulse Testing of the LAR (MIT-LAR), may remedy this situation. However, droplet instability and imprecise stimulus application thus far prevented MIT-LAR from gaining clinical relevance. We present a system comprising two alternative, custom-built stereo laryngoscopes, each offering a distinct set of properties, a droplet applicator module, and image/point cloud processing algorithms to enable a targeted, droplet-based LAR stimulation. Droplet impact site prediction (ISP) is achieved by droplet trajectory identification and spatial target reconstruction. The reconstruction and ISP accuracies were experimentally evaluated. Global spatial reconstruction errors at the glottal area of (0.3±0.3) mm and (0.4±0.3) mm and global ISP errors of (0.9±0.6) mm and (1.3±0.8) mm were found for a rod lens-based and an alternative, fiberoptic laryngoscope, respectively. In the case of the rod lens-based system, 96% of all observed ISP error values are inferior to 2 mm; a value of 80% was found with the fiberoptic assembly. This contribution represents an important step towards introducing a reproducible and objective LAR screening method into the clinical routine.

Highlights

According to the World Health Organization, lower respiratory infections were on the fourth position of the global list of cause-specific mortality in 2019 [1]
Global intracloud distances of (0.12 ± 0.05) mm and (0.48 ± 0.13) mm were obtained with the rod lens-based and the fiberoptic stereo laryngoscope, respectively
The ground truth (GT) and stereoscopically reconstructed (SR) point clouds are provided as supporting material in an IEEE DataPort dataset [41]

Summary

Introduction

According to the World Health Organization, lower respiratory infections were on the fourth position of the global list of cause-specific mortality in 2019 [1]. The laryngeal adductor reflex (LAR) is one of the vital protective reflexes of the human airways. This reflex leads to a fast closure of the larynx after impact of a foreign particle, preventing the external matter from entering the lower respiratory system. Clinical research on the LAR has allowed to identify two, presumably independent, components of the LAR [4]. These components, commonly referred to as (L)R1 and (L)R2 [5], [6], are distinct with regard to their location and onset latency.

Methods

Results

Conclusion