Manuel Natividad

Videostroboscopy of Human Vocal Fold Paralysis

Previous stroboscopic studies of human vocal cord paralysis have been infrequent and have lacked documentation of the site of lesion. In order to study human laryngeal paralysis, the recurrent and superior laryngeal nerves were infiltrated unilaterally with lidocaine hydrochloride in three human volunteers. Vagal paralysis was simulated by combined (superior and recurrent) infiltration in one volunteer. Additionally, 20 patients with untreated laryngeal paralysis were studied from the voice laboratory at UCLA. In addition to videostroboscopic analysis, photoglottography and electroglottography were performed and synchronized with the stroboscopic images. The most significant finding in stroboscopy of the paralyzed larynx was the asymmetry of traveling wave motion. The traveling wave on the normal vocal fold had a faster wave velocity that created a phase difference in the vibration of the two folds. The wave also traversed a greater distance along the vocal fold mucosa on the normal side. No patient or volunteer with untreated laryngeal paralysis had a symmetric traveling wave, either in superior or recurrent laryngeal nerve paralysis. Synchronization with glottography indicated that the differentiated electroglottographic waveform provides useful information about the timing of glottic opening and closure in states of asymmetric laryngeal vibration. Implications for future studies and for the diagnosis of laryngeal paralysis are discussed.

Effect of superior laryngeal nerve stimulation on phonation in an in vivo canine model

We investigated the effect of variation in superior laryngeal nerve stimulation (SLNS) on vocal fold vibration. Photoglottography (PGG), electroglottography (EGG), and subglottic pressure (Psub) were measured in seven mongrel dogs using an in vivo canine model of phonation. The PGG, EGG, and Psub signals were examined at three SLNS frequencies (100 Hz, 130 Hz, and 160 Hz) using a constant rate of air flow. Increasing SLNS, which causes a contraction of the cricothyroid muscle, produced a marked increase in Fo, little change in Psub, an increase in the open quotient, and a decrease in the closed quotient of the glottal cycle.

The effect of air flow and medial adductory compression on vocal efficiency and glottal vibration.

This study used an in vivo canine model to investigate the effects of varying vocal fold resistance by electrically stimulating the recurrent laryngeal nerve while monitoring medial adductory compression of the vocal folds, glottal airflow, and vocal intensity. The effects of increasing airflow on glottal vibration were also examined stroboscopically and by measurement of open quotient. The results indicated that increasing intensity by medial adductory compression was more efficient than by increasing airflow. Increasing airflow produced a significantly greater open quotient and vocal fold vibratory excursion.

The effect of recurrent laryngeal nerve stimulation on phonation in an in vivo canine model.

The present investigation was designed to examine the effect of variation in recurrent laryngeal nerve stimulation (RLNS) on vocal fold vibration. Photoglottography (PGG), electroglottog‐raphy (EGG), and subglottic pressure (Psub) were measured in seven mongrel dogs using an in vivo canine model of phonation. The PGG, EGG, and Psub signals were examined at three fundamental frequencies (F0) (100 Hz, 130 Hz, and 160 Hz) for RLNS, using a constant rate of air flow. Increasing RLNS, which caused activation of the intrinsic laryngeal muscles, produced a modest increase in F0, a marked increase in Psub, no change in the open quotient (OQ), and an increase in the closing quotient (CQ). Phase quotient (Qp), which describes the interval between opening of the lower and upper fold margins, decreased with increasing RLNS.

Experimental evidence in the in vivo canine for the collapsible tube model of phonation

The in vivo canine model of the larynx was used to measure transglottic pressures and airflow during phonation. Conditions of supraglottal resistance were also simulated. Pressure drop-flow curves were compared with data on collapsible tubes. The in vivo in canine model of the larynx demonstrates a number of features similar to oscillation in collapsible tubes.

Physiologic motion after vocal cord reinnervation: A preliminary study

This study attempted to reestablish physiologic vocal cord motion, rather than synkinesis, to a rein‐nervated vocal cord. One mongrel dog underwent a division and reanastomosis of the anterior branch of the right recurrent laryngeal nerve and simultaneous separation and reimplantation of a posterior division nerve‐muscle pedicle into the posterior cricoarytenoid muscle. After 21 weeks, spontaneous physiologic vocal cord movement and electromyographic (EMG) activity were recorded during respiratory obstruction and laryngeal mechanical stimulation. Acoustic measures and histologic data are also presented from the reinnervated and normal vocalis muscle and from the recurrent laryngeal nerve. This study demonstrated that physiologic vocal cord motion can be achieved after laryngeal reinnervation using this technique.

Synchronizing videostroboscopic images of human laryngeal vibration with physiological signals

PURPOSE This report describes a new system that permits the precise correlation of videostroboscopic images with corresponding physiological measures, such as glottography and subglottic pressure. METHOD A healthy volunteer had unilateral vocal cord paralysis induced by infiltrating local anesthesia into the recurrent and superior laryngeal nerve. Vocal-fold vibrations were monitored by photoglottography (PGG) and electroglottography (EGG). Analog signals from the EGG and PGG were synchronized with the video and correlated. RESULTS The method described permits images to be sampled throughout sustained phonation. This technique allows study of events during glottic vibration. Results obtained have been in close agreement with previous studies that correlate the vocal-fold morphology to glottographic signal using other methods. This technique is inexpensive in comparison with high-speed filming. The main disadvantage of this method is related to the limitations of stroboscopy.

Regional blood flow of the canine vocal cord: the microsphere surface technique.

The vocal folds microcirculation has been well described, but there are few reports regarding the blood flow to this region. A number of methods have been used to evaluate the blood flow to an organ system. Among the most sensitive is the microsphere surface technique, which has been used to measure blood flow in many organ systems, including the cochlea. In this study, the blood flow to the canine vocal fold was assessed using the microsphere surface technique. Overall flow was measured, as well as flow to the lamina propria and muscularis layers. The technique and the results are reported.

Regional Blood Flow to the Canine Vocal Fold Rest and during Phonation

Recent reports have suggested that blood flow to the vocal fold decreases during phonation. However, these studies relied on indirect measures of blood flow, such as tissue oxygen tension. Among the differing methods of measuring blood flow, one of the most sensitive is the microsphere surface technique. This technique has been effective in assessing the overall and regional blood flow to a number of different organs, including the cochlea. Employing an in vivo canine model, we injected microspheres into the left atrium. From there, they were distributed and became entrapped in the tissues in proportion to blood flow. We measured the blood flow to the entire vocal fold, as well as the lamina propria and muscularis layers. The results revealed a statistically significant (p<.002) increase in blood flow on phonation. The increase, however, was due to increased flow to the muscularis layer. The flow to the lamina propria remained unchanged during phonation.

The effect of tension, stiffness, and air flow on laryngeal resistance in the in vivo canine model

Recent studies have indicated that glottal resistance varies inversely as a function of flow rate [M. E. Smith and G. S. Berke, J. Acoust. Soc. Am. Suppl. 1 85, S147 (1989)]. This study used an in vivo canine model to determine the effect of air flow on glottal resistance at low, medium, and high levels of recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN) stimulation. The data indicate that glottal resistance is linearly and inversely proportional to the log of air flow for low and medium levels of SLN stimulation. At air flow greater than 500 cc/s, the glottal resistances approached 0.1 mm Hg/cc/s for all levels of RLN and SLN stimulation. For low levels of air flow less than 100 cc/s, the glottal resistance was proportional to the degree of RLN and SLN stimulation.