Droplet applicator module for reproducible and controlled endoscopic laryngeal adductor reflex stimulation

Fast, Jacob Friedemann; Westermann, Konrad; Laves, Max-Heinrich; Jungheim, M.; Ptok, M.; Ortmaier, Tobias; Kahrs, Lüder A.

doi:10.1063/5.0004351

Cited by 3 publications

(10 citation statements)

References 57 publications

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“…Part II-A describes the design, manufacturing, and assembly of two different stereo laryngoscopes according to the specific requirements of a targeted MIT-LAR procedure. These optical systems were combined with an endoscopic droplet applicator module, characterized previously [27], incorporating a solenoid valve and an external fluid system pressure control circuit for stable and reproducible droplet formation. The components of the setup are shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…In our recent work, we optimized the droplet applicator module of the original MIT-LAR system [23] to achieve stable droplet formation and muzzle energy variation [27].…”

Section: B Microdroplet Impulse Testing Of the Larmentioning

confidence: 99%

“…A droplet applicator module, enabling the reproducible formation of a single stimulation droplet at a known muzzle energy, which was developed and characterized in a previous contribution [27], was attached to the side of the stereo laryngoscopes. The stability and visibility of the formed droplets was enhanced by addition of sodium chloride and the nontoxic food colorant E 150c [27].…”

Section: ) Droplet Applicator Modulementioning

confidence: 99%

“…This section describes the algorithm for the approximation of the spatial trajectory of a droplet, which is assumed to be highly reproducible after droplet applicator module optimization [27], to enable the visualization of the predicted droplet impact site for the clinician performing MIT-LAR. Fig.…”

Section: Droplet Trajectory Identificationmentioning

confidence: 99%

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

et al. 2021

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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, dropletbased 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.INDEX TERMS Aspiration, biomedical engineering, computer aided diagnosis, endoscopes, image guidance, laryngeal closure reflex, reflex latency, stereo endoscopy.

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Section: Methodsmentioning

confidence: 99%

“…In our recent work, we optimized the droplet applicator module of the original MIT-LAR system [23] to achieve stable droplet formation and muzzle energy variation [27].…”

Section: B Microdroplet Impulse Testing Of the Larmentioning

confidence: 99%

Section: ) Droplet Applicator Modulementioning

confidence: 99%

Section: Droplet Trajectory Identificationmentioning

confidence: 99%

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

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“…Fluid system pressure should be controlled by an autonomous system to further increase usability. 41,42…”

Section: Limitationsmentioning

confidence: 99%

Upper Esophageal Sphincter Response to Laryngeal Adductor Reflex Elicitation in Humans

et al. 2020

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The laryngeal adductor reflex (LAR) is an important mechanism to secure the airways from potential foreign body aspiration. An involvement of the upper esophageal sphincter (UES) in terms of a laryngo-UES contractile reflex has been identified after laryngeal mucosa stimulation. However, the LAR-UES relationship has not yet been fully explained. This study aimed to determine the magnitude, latency, and occurrence rate of the UES pressure response when the LAR is triggered in order to elucidate the functional relationship between the larynx and the UES.Methods: This prospective study included seven healthy volunteers (5 female, 2 male, age 22-34 years). Laryngeal penetration was simulated by eliciting the LAR 20 times in each individual by applying water-based microdroplets onto the laryngeal mucosa. UES pressures were measured simultaneously using high-resolution manometry.Results: Two distinct pressure phases (P1, P2) associated with the LAR were identified. P1 corresponded with a shortterm UES pressure decrease in two subjects and a pressure increase in five subjects occurring 200 to 500 ms after the stimulus. In P2, all subjects experienced an increase in UES pressure with a latency time of approximately 800 to 1700 ms and an average of 40 to 90 mmHg above the UES resting tone.Conclusion: Foreign bodies penetrating the laryngeal inlet lead to a reflex contraction of the UES. Phase P1 could be a result of vocal fold activity caused by the LAR, leading to pressure changes in the UES. The constriction during P2 could strengthen the barrier function of the UES in preparation to a subsequent cough that may be triggered to clear the airways.

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Computational Analysis of the Droplet‐Stimulated Laryngeal Adductor Reflex in High‐Speed Sequences

et al. 2022

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Objectives/Hypothesis The laryngeal adductor reflex (LAR) is an important protective mechanism of the airways. Its physiology is still not completely understood. The available methods for LAR evaluation offer limited reproducibility and/or rely on subjective interpretation. A new approach, termed Microdroplet Impulse Testing of the LAR (MIT‐LAR), was recently introduced. Here, the LAR is elicited by a droplet and a laryngoscopic high‐speed recording is acquired simultaneously. In the present work, image‐processing algorithms for autonomous MIT‐LAR sequence analysis were developed. This allowed the automated approximation of kinematic LAR parameters in humans. Study Design Development and testing of computational methods. Methods Computational image processing enabled the autonomous estimation of the glottal area, the glottal angle, and the vocal fold edge distance in MIT‐LAR sequences. A suitable analytical representation of these glottal parameters allowed the extraction of seven relevant LAR parameters. The obtained values were compared to the literature. Results A generalized logistic function showed the highest average goodness of fit among four different analytical approaches for each of the glottal parameters. Autonomous sequence analysis yielded bilateral LAR response latencies of (229 ± 116) ms and (182 ± 60) ms for cases of complete and incomplete glottal closure, respectively. The initial/average/maximum angular vocal fold adduction velocity was estimated at (157 ± 115) °s−1/(891 ± 516) °s−1/(929 ± 583) °s−1 and (88 ± 53) °s−1/(421 ± 221) °s−1/(520 ± 238) °s−1 for complete and incomplete glottal closure, respectively. Conclusion The automated extraction of LAR parameters from laryngoscopic high‐speed sequences can potentially increase the objectiveness of optical LAR characterization and reduce the associated workload. The proposed methods may thus be helpful for future research on this vital reflex. Level of Evidence NA Laryngoscope, 132:2412–2419, 2022

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Droplet applicator module for reproducible and controlled endoscopic laryngeal adductor reflex stimulation

Cited by 3 publications

References 57 publications

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

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

Upper Esophageal Sphincter Response to Laryngeal Adductor Reflex Elicitation in Humans

Computational Analysis of the Droplet‐Stimulated Laryngeal Adductor Reflex in High‐Speed Sequences

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