Controlling the variability of air-pulses to determine the thresholds of laryngeal-pharyngeal reflexes using a novel device (original) (raw)
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Ludlow Laryngeal reflexes J Clin Neurophysiol 2015
This review examines the current level of knowledge and techniques available for the study of laryngeal reflexes. Overall, the larynx is under constant control of several systems (including respiration, swallowing and cough) as well as sensory motor reflex responses involving glossopharyngeal, pharyngeal, laryngeal, and tracheobronchial sensory receptors. Techniques for the clinical assessment of these reflexes are emerging and need to be examined for sensitivity and specificity in identifying laryngeal sensory disorders. Quantitative assessment methods for the diagnosis of sensory reductions and sensory hypersensitivity may account for laryngeal disorders, such as chronic cough, paradoxical vocal fold disorder, and muscular tension dysphonia. The development of accurate assessment techniques could improve our understanding of the mechanisms involved in these disorders.
Background: Laryngo‑pharyngeal mechano‑sensitivity (LPMS) is involved in dyspha‑ gia, sleep apnea, stroke, irritable larynx syndrome and cough hypersensitivity syndrome among other disorders. These conditions are associated with a wide range of airway reflex abnormalities. However, the current device for exploring LPMS is limited because it assesses only the laryngeal adductor reflex during fiber‑optic endoscopic evalua‑ tions of swallowing and requires a high degree of expertise to obtain reliable results, introducing intrinsic expert variability and subjectivity. Methods: We designed, developed and validated a new air‑pulse laryngo‑pharyngeal endoscopic esthesiometer with a built‑in laser range‑finder (LPEER) based on the eval‑ uation and control of air‑pulse variability determinants and on intrinsic observer vari‑ ability and subjectivity determinants of the distance, angle and site of stimulus impact. The LPEER was designed to be capable of delivering precise and accurate stimuli with a wide range of intensities that can explore most laryngo‑pharyngeal reflexes. Results: We initially explored the potential factors affecting the reliability of LPMS tests and included these factors in a multiple linear regression model. The following factors significantly affected the precision and accuracy of the test (P < 0.001): the tube con‑ ducting the air‑pulses, the supply pressure of the system, the duration of the air‑pulses, and the distance and angle between the end of the tube conducting the air‑pulses and the site of impact. To control all of these factors, an LPEER consisting of an air‑pulse generator and an endoscopic laser range‑finder was designed and manufactured. We assessed the precision and accuracy of the LPEER's stimulus and range‑finder accord‑ ing to the coefficient of variation (CV) and by looking at the differences between the measured properties and the desired values, and we performed a pilot validation on ten human subjects. The air‑pulses and range‑finder exhibited good precision and accuracy (CV < 0.06), with differences between the desired and measured properties at <3 % and a range‑finder measurement error of <1 mm. The tests in patients demonstrated obtain‑ able and reproducible thresholds for the laryngeal adductor, cough and gag reflexes. Conclusions: The new LPEER was capable of delivering precise and accurate stimuli for exploring laryngo‑pharyngeal reflexes.
Laryngeal reflex responses are not modulated during human voice and respiratory tasks
The Journal of Physiology, 2007
Poletto, Christopher J., Laura P. Verdun, Robert Strominger, and Christy L. Ludlow. Correspondence between laryngeal vocal fold movement and muscle activity during speech and nonspeech gestures. To better understand the role of each of the laryngeal muscles in producing vocal fold movement, activation of these muscles was correlated with laryngeal movement during different tasks such as sniff, cough or throat clear, and speech syllable production. Four muscles [the posterior cricoarytenoid, lateral cricoarytenoid, cricothyroid (CT), and thyroarytenoid (TA)] were recorded with bipolar hooked wire electrodes placed bilaterally in four normal subjects. A nasoendoscope was used to record vocal fold movement while simultaneously recording muscle activity. Muscle activation level was correlated with ipsilateral vocal fold angle for vocal fold opening and closing. Pearson correlation coefficients and their statistical significance were computed for each trial. Significant effects of muscle (P Յ 0.0005) and task (P ϭ 0.034) were found on the r (transformed to Fisher's ZЈ) values. All of the posterior cricoarytenoid recordings related significantly with vocal opening, whereas CT activity was significantly correlated with opening only during sniff. The TA and lateral cricoarytenoid activities were significantly correlated with vocal fold closing during cough. During speech, the CT and TA activity correlated with both opening and closing. Laryngeal muscle patterning to produce vocal fold movement differed across tasks; reciprocal muscle activity only occurred on cough, whereas speech and sniff often involved simultaneous contraction of muscle antagonists. In conclusion, different combinations of muscle activation are used for biomechanical control of vocal fold opening and closing movements during respiratory, airway protection, and speech tasks.