Design of a new somatosensory stimulus delivery device for measuring laryngeal mechanosensory detection thresholds in humans

Abstract

Laryngeal control is essential for airway protection, breathing, deglutition, speech, and voice. Unfortunately, integration of laryngeal sensory assessment in research and clinical practice is limited by technical and practical limitations of commercially available technology. A commercial device is available, but reported limitations include procedural complexity requiring two or three individuals to operate, limited stimulus dynamic range, device generated noise, and questionable stimulus reproducibility. The objective of this study was to design a new laryngeal somatosensory stimulus delivery device that provides direct, reliable control over the timing, duration, and dynamic range of stimulus presentation, and test the device in individuals who may manifest a laryngeal sensory deficit. The new device operates silently and has more than four times greater stimulus dynamic range than the commercial device. Testing with the new device revealed laryngeal mechanosensory detection thresholds in an individual with Parkinson's disease that were seven times higher than those of healthy controls. These data would have otherwise gone undetected due to limited stimulus dynamic range in the commercial device. The new design resulted in a new assessment instrument that is simple to use for routine clinical assessment, yet sufficiently versatile for integration within rigorous clinical research protocols.

Figures

Fig. 1

Block diagram of the stimulus delivery paradigm. The air stimulus is directed to the laryngeal mucosa through a port in the laryngoscope as visualized on the monitor. The +5-V signal from a hand-held switch indicates when the participant feels the laryngeal somatosensory stimulus.

Fig. 2

Stimulus waveforms for the new laryngeal somatosensory stimulus delivery device (left panel) and the commercial device (right panel).

Fig. 3

LMDT was measured for five healthy controls and PD1 using the commercial device (L: left arytenoid mucosa; R: right arytenoid mucosa). Stimulus duration was fixed at 50 ms. LMDT was not measurable (#) because controls felt the lowest stimulus of the commercial device (2 mm Hg) 100% of the time. LMDT was not measurable (+) because PD1 OFF felt the highest stimulus of the commercial device (10 mm Hg)

Fig. 4

LMDT was measured for five healthy controls and five participants with PD using the new device. A 135-ms stimulus duration was used. LMDT was measurable for all participants. Bar height represents mean LMDT with standard error of the mean for each condition. LMDT for PD-OFF and PD-ON were each significantly higher than controls (p < 0.01). There was a nonsignificant trend for LMDTs to decrease (PD-OFF versus PD-ON) following medication (p > 0.01).