Surface Electromyographic Activity in Total Laryngectomy Patients following Laryngeal Nerve Transfer to Neck Strap Muscles

Hands-free triggering and pitch control would improve electrolarynx devices, which are inconvenient to use and sound unnatural. The present study tested the strategy of salvaging voice-related neural signals for hands-free electrolarynx control either by transferring cut recurrent laryngeal nerves (RLNs) to denervated neck strap muscles or by preserving strap muscles with their normal innervation. An RLN nerve transfer was performed at the time of total laryngectomy in 8 individuals, and in 5 of these subjects, strap muscles with intact ansa cervicalis innervation were also preserved for comparison. Neck surface electromyography performed over the strap muscles was used periodically for more than 1 year on phonatory and nonphonatory tasks. Signals were eventually obtained in all subjects from both RLN-innervated and ansa-innervated strap muscles that correlated with speech production. After 1 year, RLN-driven signals were larger than ansa-driven signals in magnitude, and their timing appeared better correlated with intended phonation. The results show that neck surface electromyography is an effective control source for hands-free electrolarynx activation, and that RLN transfer may provide the best approach for obtaining phonation-related activity.

Training effects on speech production using a hands-free electromyographically controlled electrolarynx

PURPOSE

The electrolarynx (EL) is a widely used device for alaryngeal speech, but it requires manual operation and produces voice that typically has a constant fundamental frequency. An electromyographically controlled EL (EMG-EL) was designed and implemented to provide hands-free control with dynamic pitch modulation.

METHOD

Three participants who underwent total laryngectomy surgery and 4 participants with normal voice were trained to produce EMG-EL speech through a multiple-baseline, successive-stage protocol. Baseline performance was established through 3 testing probes, followed by multiple hour-long training sessions.

RESULTS

At the end of the training, all participants learned to initiate, sustain, and terminate EMG-EL activation in correspondence with articulation, and most were able to modulate the pitch to produce intonational contrasts. After completing the testing/training protocol, 1 of the 3 participants who underwent total laryngectomy was encouraged to independently use the EMG-EL at his residence. This participant sustained his performance for an additional 6 weeks and also used the EMG-EL successfully to communicate over the phone.

CONCLUSIONS

Our findings suggest that some participants with laryngectomies and vocally normal individuals can learn to produce hands-free speech using the EMG-EL device within a few hours and that significant additional gains in device control (particularly pitch modulation) are attainable through subsequent training sessions.

Design and Implementation of a Hands-Free Electrolarynx Device Controlled by Neck Strap Muscle Electromyographic Activity

The electrolarynx (EL) voice prosthesis is widely used, but suffers from the inconvenience of requiring manual control. Therefore, a hands-free EL triggered by neck muscle electromyographic (EMG) activity was developed (EMG-EL). Signal processing circuitry in a belt-mounted control unit transforms EMG activity into control signals for initiation and termination of voicing. These control signals are then fed to an EL held against the neck by an inconspicuous brace. Performance of the EMG-EL was evaluated by comparison to normal voice, manual EL voice, and tracheo-esophageal (TE) voice in a series of reaction time experiments in seven normal subjects and one laryngectomy patient. The normal subjects produced voice initiation with the EMG-EL that was as fast as both normal voice and the manual EL. The laryngectomy subject produced voice initiation that was slower than with the manual EL, but faster than with TE voice. Voice termination with the EMG-EL was slower than normal voice for the normal subjects, but not significantly different than with the manual EL. The laryngectomy subject produced voice termination with the EMG-EL that was slower than with TE or manual EL. The EMG-EL threshold was set at 10% of the range of vocal-related EMG activity above baseline. Simulations of EMG-EL behavior showed that the 10% threshold was not significantly different from the optimum threshold produced through the process of error minimization. The EMG-EL voice reaction time appears to be adequate for use in a day-to-day conversation.

Recurrent laryngeal nerve transposition in guinea pigs

Improved control of prosthetic voice aids for laryngectomees might be possible to obtain with residual laryngeal motor nerve signals. We were able to recover motor signals from the recurrent laryngeal nerve (RLN) by transposing it into the ipsilateral denervated sternohyoid muscle (SH) in 8 guinea pigs. Reinnervation was monitored by electromyographic recordings from surface and intramuscular needle electrodes in awake animals. Within 4 to 14 weeks after surgery, all animals demonstrated laryngeal-like motor activity in the reinnervated SH, including activity during respiration, sniffing, swallowing, and/or vocalizing. After 3 to 6 months, the animals were reanesthetized, and nerve stimulation and section experiments confirmed the RLN as the source of reinnervation in all cases. In several animals, activity of the RLN-innervated SH was demonstrated to be correlated with that of contralateral laryngeal muscles. Histochemical analysis of the SH indicated a unilateral transformation from mostly fatigable to mostly fatigue-resistant fiber types ipsilateral to the RLN transposition, a phenotype more typical of laryngeal muscles. Thus, RLN transposition at the time of laryngectomy may be a method for salvaging laryngeal control signals that could be used to control prosthetic voice devices.

The effect of nail polish on pulse oximetry

A randomized, blind study examined the effect of nail polish color on measurement of oxygen saturation by pulse oximetry. Fourteen adult volunteers had blue, green, purple, black, and red nail polish applied to their finger nails. A strip-chart recording of oxygen saturation (Nellcor N100) was made in room air and later interpreted in a blinded fashion. The absorption spectra of the five polishes were determined by spectrophotometry. The spectra of nine other nail polishes and three intravenous dyes also were examined. Black, blue, and green nail polish significantly lowered oximeter readings of oxygen saturation. Blue and green produced greater decreases than purple and red; black produced an intermediate decrease. Some but not all nail polishes absorbed light at the wavelengths used by the pulse oximeter (660 nm and 940 nm). The degree of artifactual desaturation correlated best with the difference between absorbance at 660 nm and absorbance at 940 nm (r = 0.95). Spectrophotometric absorbance data suggest that other colors may interfere with pulse oximetry. On the basis of spectrophotometric data, brown-red nail polish was predicted to interfere with oximetry; subsequent pulse oximetry measurements confirmed the prediction. Nail polish should be removed routinely before pulse oximetry monitoring.

A single-blind study of pulse oximetry in children

Oxygen saturation determined by pulse oximetry was monitored in 152 pediatric surgical patients divided into two groups. In one group, the oximeter data and alarms were available (N = 76) to the anesthesia team, and, in the other group, these data were unavailable (N = 76). A trained observer recorded all intraoperative hypoxic episodes and informed the anesthesia team of all major events (i.e., oxygen saturation less than or equal to 85% for greater than or equal to 30 s) (PaO2 approximately 52 mmHg). Thirty-five major events occurred: 24 in the unavailable group, and 11 in the available group (P = 0.021). A greater number of major events occurred in children less than or equal to 2 yr of age (P = 0.013). Hypoxic events diagnosed by the oximeter, but not by the anesthesiologist, were more frequent in the unavailable group (13) than in the available group (5) (P = 0.0495). ASA Physical Status 3 and 4 patients were more likely to suffer a major event (P = 0.009 available, 0.006 unavailable). The pulse oximeter diagnosed hypoxemia before the signs and symptoms of hypoxemia were apparent (i.e., prior to observed cyanosis or bradycardia). Major hypoxic events were unrelated to duration of anesthesia. Major events were evenly distributed among induction, maintenance, and awakening from anesthesia; a greater number of hypoxic events occurred during induction in the unavailable group (P = 0.031). No morbidity was documented in any patient who suffered an hypoxic event.(ABSTRACT TRUNCATED AT 250 WORDS)