Validation of the TruBlue Light Laser for Laryngeal Somatosensory and Perturbation Testing

Clinical assessment of laryngeal somatosensation is limited by the lack of precise tools to directly stimulate the larynx and quantify sensorimotor responses. This study validated a blue light laser method for laryngeal somatosensory testing in vocally healthy adults and developed acoustic measures to quantify vocal responses to controlled laryngeal perturbations.

In this prospective validation study, a 445-nm diode blue light laser was delivered through a channeled flexible laryngoscope to the arytenoid mucosa. Single subablative pulses (1-10 W, 30 ms) were applied during quiet breathing or sustained phonation to determine perceptual and reflexive sensory thresholds, discrimination acuity, and laryngeal perturbation responses. Acoustic recordings during perturbations were analyzed in Praat using custom software to extract continuous fundamental frequency variability and quantify perturbation magnitude and recovery.

Participants demonstrated reliable perceptual detection and laryngeal reflexive responses to laser stimulation. Mean perceptual sensory threshold was 1.46 W (SD = 1.17) and mean laryngeal response threshold was 4.62 W (SD = 2.04). Sensory ratings were higher during stimulation than foil trials (p < 0.001). Sensory perception increased with stimulation intensity (~0.3 points per 1 W; p < 0.001), and higher wattage increased odds of eliciting a laryngeal response (OR = 1.38; p < 0.001). Discrimination accuracy averaged 78.5% (OR = 1.45; p = 0.002). Laser stimulation during phonation produced measurable acoustic perturbations (peak SD(f₀) = 19.35 Hz; recovery = 0.48 s).

Blue light laser stimulation is a feasible and precise method for evaluating laryngeal somatosensation and vocal sensorimotor responses.