BackgroundLaryngeal dystonia is a task-specific focal dystonia of laryngeal muscles that impairs speech and voice production. At present, there is no cure for LD. The most common therapeutic option for patients with LD involves Botulinum neurotoxin injections.ObjectiveProvide empirical evidence that non-invasive vibro-tactile stimulation (VTS) of the skin over the voice box can provide symptom relief to those affected by LD.MethodsSingle-group 11-week randomized controlled trial with a crossover between two dosages (20 min of VTS once or 3 times per week) self-administered in-home in two 4-week blocks. Acute effects of VTS on voice and speech were assessed in-lab at weeks 1, 6 and 11. Participants were randomized to receive either 40 Hz or 100 Hz VTS.Main outcome measuresPrimary: smoothed cepstral peak prominence (CPPS) of the voice signal to quantify voice and speech abnormalities, and perceived speech effort (PSE) ranked by participants as a measure of voice effort (scale 1–10). Secondary: number of voice breaks during continuous speech, the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) inventory as a measure of overall disease severity and the Voice Handicap Index 30-item self report.ResultsThirty-nine people with a confirmed diagnosis of adductor-type LD (mean [SD] age, 60.3 [11.3] years; 18 women and 21 men) completed the study. A single application of VTS improved voice quality (median CPPS increase: 0.41 dB, 95% CI [0.20, 0.61]) and/or reduced voice effort (PSE) by at least 30% in up to 57% of participants across the three study visits. Effects lasted from less than 30 min to several days. There was no effect of dosage and no evidence that the acute therapeutic effects of VTS increased or decreased longitudinally over the 11-week study period. Both 100 and 40 Hz VTS induced measurable improvements in voice quality and speech effort. VTS induced an additional benefit to those receiving Botulinum toxin. Participants, not receiving Botulinum treatment also responded to VTS.ConclusionThis study provides the first systematic empirical evidence that the prolonged use of laryngeal VTS can induce repeatable acute improvements in voice quality and reductions of voice effort in LD.Clinical trial registrationClinicalTrials.gov ID: NCT03746509.

Purpose: This study aimed to describe the utility of phonation threshold pressure (PTP) measurement as an additional outcome measure for changes in vocal fold vibration secondary to submucosal saline injection in the case of an individual with idiopathic vocal fold scarring. Method: An 8-week program of voice therapy, followed by submucosal saline infusion, was administered, using multiple outcome measures to assess voice quality, effort, and function in a 38-year-old woman with idiopathic bilateral vocal fold scarring. Transoral rigid video-endoscopy with stroboscopy in conjunction with the Stroboscopy Evaluation Rating Form provided measures of the vibratory characteristics of the vocal folds (amplitude, mucosal wave, nonvibratory portion, edge smoothness, and straightness). Auditory-perceptual measures were obtained using the Consensus Auditory-Perceptual Evaluation of Voice. Acoustic measures included jitter (%local), shimmer (%local), harmonics-to-noise ratio (dB), and Cepstral Spectral Index of Dysphonia. Additionally, PTP was measured 1 day prior to, and 1 month after, saline infusion. Results: Acoustic, auditory-perceptual, and stroboscopic variables suggested minimal change to the vibratory properties of the vocal folds in response to submucosal saline infusion for the treatment of vocal fold scarring. PTP measurements across the patient's frequency range, however, revealed a marked decrease post infusion. This was consistent with the patient's report of improved functioning and her request for repeat saline infusion. Conclusion: These results are consistent with the possibility of using PTP as an independent means of quantifying changes in phonatory physiology across the frequency range in patients with vocal fold scarring. Supplemental Material: https://doi.org/10.23641/asha.21313725

Purpose The effects of neuromodulation are virtually unexplored in adductor laryngeal dystonia (AdLD), a disorder characterized by involuntary contraction of intrinsic laryngeal muscles. Recent findings indicated that intracortical inhibition is reduced in people with AdLD. Low-frequency repetitive transcranial magnetic stimulation (rTMS) induces prolonged intracortical inhibition, but the effects in AdLD are unexplored. This pilot and feasibility study aimed to examine the safety, feasibility, and effects of a single session 1 Hz rTMS over the laryngeal motor cortex (LMC) in people with AdLD and healthy individuals. Methods The stimulation location was individualized and determined through TMS-evoked responses in the thyroarytenoid muscles using fine-wire electrodes. 1200 pulses of 1 Hz rTMS were delivered to the left LMC in two groups: Control (n = 6) and AdLD (n = 7). Tolerance, adverse effects, intracortical inhibition, and voice recordings were collected immediately before and after rTMS. Voice quality was assessed with acoustic-based and auditory-perceptual measures. Results All participants tolerated the procedures, with no unexpected adverse events or worsening of symptoms. No significant effects on intracortical inhibition were observed. In the AdLD group, there was a large-effect size after rTMS in vocal perturbation measures and a small-effect size in decreased phonatory breaks. Conclusions One rTMS session over the LMC is safe and feasible, and demonstrated trends of beneficial effects on voice quality and phonatory function in AdLD. These preliminary findings support further investigation to assess clinical benefits in a future randomized sham-controlled trial. ClinicalTrials.gov NCT02957942, registered on November 8, 2016.

BACKGROUND:Reduced intracortical inhibition is a neurophysiologic finding in focal dystonia that suggests a broader problem of impaired cortical excitability within the brain. A robust understanding of the neurophysiology in dystonia is essential to elucidate the pathophysiology of the disorder and develop new treatments. The cortical silent period (cSP) is a reliable, non-invasive method to measure intracortical inhibition in the primary motor cortex associated with a muscle of interest. In adductor spasmodic dysphonia (AdSD), cSP of the laryngeal motor cortex (LMC) which directly corresponds to the affected musculature, the thyroarytenoid (TA), has not been examined. OBJECTIVE:This work evaluated the cSP of the LMC and the relationship between cSP and functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) activation in people with AdSD (n = 12) compared to healthy controls (CTL, n = 14). RESULTS:Shortened LMC cSP were observed bilaterally in people with AdSD vs CTL (F(1, 99) = 19.5226, p < 0.0001), with a large effect size (η2 = 0.1834). Between-group fMRI analysis revealed greater activation in bilateral LMC in the AdSD > CTL contrast as compared to CTL > AdSD contrast. Correlation analysis showed that people with AdSD have positive correlation of left LMC BOLD activation and the cSP. Further, the right LMC cSP lacks either positive or negative associations with BOLD activation. CTL individuals displayed both positive and negative correlations between cSP and BOLD activation in the left LMC. In CTL, the LMC cSP and BOLD activation showed exclusively negative correlations in both hemispheres. CONCLUSION:In AdSD, the cortical activation during phonation may not be efficiently or effectively associated with inhibitory processes, leading to muscular dysfunction. These findings may give insight into the maladaptive cortical control during phonation in people with AdSD.

University of Minnesota Ph.D. dissertation.March 2021. Major: Kinesiology. Advisor: Juergen Koncak. 1 computer file (PDF); xiii, 105 pages.

Objective: Spasmodic dysphonia (SD) is a debilitating voice/speech disorder without an effective cure. To obtain a better understanding of the underlying cortical neural mechanism of the disease we analyzed electroencephalographic (EEG) signals of people with SD during voice production. Method: Ten SD individuals and 10 healthy volunteers produced 50 vowel vocalization epochs of 2500 ms duration. Two EEG features were derived: (1) event-related change in spectral power during vocalization relative to rest, (2) inter-regional spectral coherence. Results: During early vocalization (500-1000 ms) the SD group showed significantly larger alpha band spectral power over the left motor cortex. During late vocalization (1000-2500 ms) SD patients showed a significantly larger gamma band coherence between left somatosensory and premotor cortical areas. Conclusions: Two atypical patterns of cortical activity characterize the pathophysiology of spasmodic dysphonia during voice production: (1) a reduced movement-related desynchronization of motor cortical networks, (2) an excessively large synchronization between left somatosensory and premotor cortical areas. Significance: The pathophysiology of SD is characterized by an abnormally high synchronous activity within and across cortical neural networks involved in voice production that is mainly lateralized in the left hemisphere. Published by Elsevier B.V. on behalf of International Federation of Clinical Neurophysiology.

Spasmodic dysphonia (SD) is an incurable focal dystonia of the larynx that impairs speech and communication. Vibro-tactile stimulation (VTS) alters afferent proprioceptive input to sensorimotor cortex that controls speech. This proof-of-concept study examined the effect of laryngeal VTS on speech quality and cortical activity in 13 SD participants who vocalized the vowel /a/ while receiving VTS for 29 minutes. In response to VTS, 9 participants (69%) exhibited a reduction of voice breaks and/or a meaningful increase in smoothed cepstral peak prominence, an acoustic measure of voice/speech quality. Symptom improvements persisted for 20 minutes past VTS. Application of VTS induced a significant suppression of theta band power over the left somatosensory-motor cortex and a significant rise of gamma rhythm over right somatosensory-motor cortex. Such suppression of theta oscillations is observed in patients with cervical dystonia who apply effective sensory tricks, suggesting that VTS in SD may activate a similar neurophysiological mechanism. Results of this feasibility study indicate that laryngeal VTS modulates neuronal synchronization over sensorimotor cortex, which can induce short-term improvements in voice quality. The effects of long-term VTS and its optimal dosage for treating voice symptoms in SD are still unknown and require further systematic study.

Objective: This work aimed to evaluate the cortical silent period (cSP) of the laryngeal motor cortex (LMC) using the bilateral thyroarytenoid (TA) muscles with transcranial magnetic stimulation (TMS). Methods: In 11 healthy participants, fine-wire electromyography (EMG) was used to record bilateral TA muscle responses to single pulse TMS delivered to the LMC in both hemispheres. Peripheral responses to stimulation over the mastoid, where the vagus nerve exits the skull, were collected to verify the central origin of the cortical stimulation responses by comparing the latencies. Results: The cSP duration ranged from 41.7 to 66.4 ms. The peripherally evoked motor-evoked potential (MEP) peak occurred 5-9 ms earlier than the cortical responses (for both sides of TAs: p < 0.0001) with no silent period. The right TA MEP latencies were earlier than the left TA responses for both peripheral and cortical measures (p ≤ 0.0001). Conclusion: These findings demonstrate the feasibility of measuring cSP of LMC based on intrinsic laryngeal muscles responses during vocalization in healthy volunteers. Significance: The technique could be used to study the pathophysiology of neurological disorders that affect TA muscles, such as spasmodic dysphonia. Further, the methodology has application to other muscles of the head and neck not accessible using surface electrodes.

Voice rest is frequently recommended following surgical disruption of vocal fold epithelium, but patients report variable adherence to voice rest recommendations. The objective of this study was to assess the clinical utility of an ambulatory vocal dosimeter for measuring adherence to voice rest recommendations.

Summary Reduced upper airway muscle activity during sleep is a key contributor to obstructive sleep apnea pathogenesis. Hypoglossal nerve stimulation activates upper airway dilator muscles, including the genioglossus, and has the potential to reduce obstructive sleep apnea severity. The objective of this study was to examine the safety, feasibility and efficacy of a novel hypoglossal nerve stimulation system ( HGNS ® ; Apnex Medical, St Paul, MN , USA ) in treating obstructive sleep apnea at 12 months following implantation. Thirty‐one subjects (35% female, age 52.4 ± 9.4 years) with moderate to severe obstructive sleep apnea and unable to tolerate positive airway pressure underwent surgical implantation and activation of the hypoglossal nerve stimulation system in a prospective single‐arm interventional trial. Primary outcomes were changes in obstructive sleep apnea severity (apnea–hypopnea index, from in‐laboratory polysomnogram) and sleep‐related quality of life [Functional Outcomes of Sleep Questionnaire ( FOSQ )]. Hypoglossal nerve stimulation was used on 86 ± 16% of nights for 5.4 ± 1.4 h per night. There was a significant improvement ( P < 0.001) from baseline to 12 months in apnea–hypopnea index (45.4 ± 17.5 to 25.3 ± 20.6 events h −1 ) and Functional Outcomes of Sleep Questionnaire score (14.2 ± 2.0 to 17.0 ± 2.4), as well as other polysomnogram and symptom measures. Outcomes were stable compared with 6 months following implantation. Three serious device‐related adverse events occurred: an infection requiring device removal; and two stimulation lead cuff dislodgements requiring replacement. There were no significant adverse events with onset later than 6 months following implantation. Hypoglossal nerve stimulation demonstrated favourable safety, feasibility and efficacy.

BACKGROUND:The aim of this study was to identify and evaluate adverse clinical outcomes following office-based sclerotherapy using sodium tetradecyl sulfate (STS) for epistaxis due to hereditary hemorrhagic telangiectasias (HHT or Osler-Weber-Rendu).METHODS:A retrospective chart review of 36 adult patients treated with STS sclerotherapy for severe and/or recurrent epistaxis due to HHT was performed.RESULTS:A total of 153 separate treatment sessions were analyzed. Each patient underwent an average of 4.3 sessions with an average of 7 intralesional injections per session. Bleeding during the procedure was experienced by 8 patients with a maximum reported blood loss of 200 mL in 1 patient, but less than 50 mL in all others. Seven patients reported some postinjection pain, which included nasal, cheek, and eye pain. Nasal congestion, sneezing, and vasovagal responses were each noted to occur 2 times. No complications of postprocedural visual loss, deep venous thrombosis/pulmonary embolus, transient ischemic attack (TIA)/stroke, or anaphylaxis were encountered.CONCLUSION:Conventional therapies used in the management of HHT-related epistaxis, such as laser coagulation, septodermoplasty, selective arterial embolization, and Young's occlusion each have specific associated complications, including worsened epistaxis, septal perforation, foul odor, nasal crusting, and compromised nasal breathing. STS is a safe office-based treatment option for HHT-mediated epistaxis that is associated with exceedingly few of the aforementioned serious sequelae.

VOCAL FOLD SWELLING: MYTHS AND FACTS THIS, THE THIRD IN A SERIES OF ARTICLES about misconceptions that singers harbor about their instruments,1 examines some myths and truths about vocal fold swelling, particularly as it pertains to upper respiratory infection (URI). Colds and flu are a pervasive part of our lives as singers, and it is clear that singers have heard a great deal of information on the topic. Much of the information is conflicting, and it comes from a wide variety of sources, such as physicians, television commercials, other singers, and grandmothers. Singers are eager to know what information is valid, and they are eager to dispel myths. VOCAL FOLD EDEMA Edema classically refers to an excess accumulation of thin or serous fluid in connective tissue-typically just beneath the skin or mucosa. This can happen anywhere in the body and is seen as swelling of the area affected. When it occurs in the vocal folds the fluid accumulates in a specialized area below the surface covering (epithelium) known as Reinke's space. Reinke's space is the gelatinous layer of the vocal fold that allows vibration at a wide variety of frequencies and configurations. When a vocal fold is edematous, or swollen, much of its ability to vibrate at higher frequencies is lost. The greater the amount of swelling there is, the greater the loss of vocal range. Swelling will also affect the smoothness and regularity of vocal fold vibration resulting in a rougher quality to the sound. Depending on the cause, edema can affect the entire length of the vibrating part of the vocal fold, or a small and discrete section. Vocal fold edema can occur from natural and legitimate causes, such as URI or hormonal status. It can also result from non-voice-related high impact activities, such as coughing or throat clearing, or high impact vocal behaviors such as prolonged, loud voice use. Many high impact vocal behaviors are perfectly legitimate, and in limited amounts should not necessarily be dangerous for a healthy larynx. Most of us can talk at a noisy party or cheer at a sporting event with no undue consequences. With a healthy larynx, if we do develop some hoarseness after loud voice use, it can resolve within a day. It is important to note that the tendency to develop vocal fold edema is highly individual, and unrelated to talent. Some individuals can yell all night with no hoarseness, and others become hoarse quickly. On the other hand, the act of loud voice use may predispose some individuals to development of edema and the consequent hoarseness. It is important for singers with needs for frequent or prolonged loud voice use to learn techniques and strategies to minimize vocal fold impact as much as possible. Vocal fold edema can be acute or chronic. Acute edema is typically reversible with time, particularly with a viral URI, or with a reduction in trauma or even voice rest. Chronic or long standing edema may be reversible, but resolution can be much more difficult. Intervention should focus on reduction or elimination of the cause of the edema to accomplish the greatest long term results. Reinke's edema is a chronic form of vocal fold edema that can be severe. It is typically seen in smokers who overuse their voices for a long period of time. There is a variable susceptibility to this disorder, however, as most people who exhibit these behaviors will not develop significant Reinke's edema. On examination of the larynx, polypoid swellings of variable size with a base along the entire vibratory surface of the vocal fold can be seen. The vocal range becomes abnormally low with a rough quality. The effects on voice quality loosely parallel the severity of the vocal swelling. Stopping tobacco use and improving vocal technique can improve voice quality, but resolution of large edematous swellings often requires surgery.2 Fortunately, most serious singers will maintain sufficient vocal and general health to avoid severe or even moderate Reinke's edema. …

OBJECTIVE:To characterize the changes in the anteroposterior dimensions of both the retropalatal and retrolingual airway spaces of the pharynx and hyoid bone position during hypoglossal nerve stimulation under general anesthesia in subjects with obstructive sleep apnea.STUDY DESIGN:Cross-sectional.SETTING:Academic center.SUBJECTS AND METHODS:Cross-table fluoroscopic images obtained during hypoglossal nerve stimulation were studied in 26 subjects enrolled in the Apnex Medical Hypoglossal Nerve Stimulation (HGNS) system feasibility trials. Changes in the anteroposterior dimensions (2-dimensional) of the retropalatal and retrolingual airway spaces and hyoid bone position were recorded. Measurements were estimated in millimeters and standardized to each subject's C3 vertebral height. Opening of the pharyngeal airspace was examined relative to body mass index.RESULTS:During hypoglossal nerve stimulation, all subjects demonstrated anterior displacement of the tongue base on fluoroscopy. The average retrolingual airway opening was 0.71 ± 0.23 C3 vertebral body heights (9 ± 3 mm). Opening of the retropalatal airway with stimulation occurred in 65% (15/23) of subjects. When present, the average opening was 0.42 ± 0.14 vertebral heights (5 ± 3 mm). Anterior displacement of the hyoid occurred in 92% (23/25) of subjects. Retrolingual airway opening was independent of baseline body mass index.CONCLUSION:Unilateral hypoglossal nerve stimulation results in anterior tongue base displacement and an increase in the anterior-posterior retrolingual airway dimensions of the pharynx, independent of body mass index. Opening of the retropalatal airway occurred in a majority of subjects and had a trend toward correlation with body mass index.

BACKGROUND Reduced upper airway muscle activity during sleep is fundamental to obstructive sleep apnea (OSA) pathogenesis. Hypoglossal nerve stimulation (HGNS) counteracts this problem, with potential to reduce OSA severity. STUDY OBJECTIVES To examine safety and efficacy of a novel HGNS system (HGNS, Apnex Medical, Inc.) in treating OSA. PARTICIPANTS Twenty-one patients, 67% male, age (mean ± SD) 53.6 ± 9.2 years, with moderate to severe OSA and unable to tolerate continuous positive airway pressure (CPAP). DESIGN Each participant underwent surgical implantation of the HGNS system in a prospective single-arm interventional trial. OSA severity was defined by apnea-hypopnea index (AHI) during in-laboratory polysomnography (PSG) at baseline and 3 and 6 months post-implant. Therapy compliance was assessed by nightly hours of use. Symptoms were assessed using the Epworth Sleepiness Scale (ESS), Functional Outcomes of Sleep Questionnaire (FOSQ), Calgary Sleep Apnea Quality of Life Index (SAQLI), and the Beck Depression Inventory (BDI). RESULTS HGNS was used on 89% ± 15% of nights (n = 21). On these nights, it was used for 5.8 ± 1.6 h per night. Nineteen of 21 participants had baseline and 6-month PSGs. There was a significant improvement (all P < 0.05) from baseline to 6 months in: AHI (43.1 ± 17.5 to 19.5 ± 16.7), ESS (12.1 ± 4.7 to 8.1 ± 4.4), FOSQ (14.4 ± 2.0 to 16.7 ± 2.2), SAQLI (3.2 ± 1.0 to 4.9 ± 1.3), and BDI (15.8 ± 9.0 to 9.7 ± 7.6). Two serious device-related adverse events occurred: an infection requiring device removal and a stimulation lead cuff dislodgement requiring replacement. CONCLUSIONS HGNS demonstrated favorable safety, efficacy, and compliance. Participants experienced a significant decrease in OSA severity and OSA-associated symptoms. CLINICAL TRIAL INFORMATION NAME: Australian Clinical Study of the Apnex Medical HGNS System to Treat Obstructive Sleep Apnea. REGISTRATION NUMBER NCT01186926. URL: http://clinicaltrials.gov/ct2/show/NCT01186926.

Background: The aim of this pilot study is to evaluate office-based sclerotherapy using sodium tetradecyl sulfate (STS) for epistaxis due to hereditary hemorrhagic telangiectasias (HHT). Patients with HHT suffer from unpredictable, recurrent, severe nasal bleeding necessitating emergency care, nasal packing, blood transfusions, and invasive procedures.Methods: In this retrospective study 7 patients with a history of treatment for recurrent epistaxis due to HHT were treated in an office-based setting with intralesional injection of STS. Treatment results were evaluated using a questionnaire. All patients had undergone multiple prior procedures attempting to control epistaxis.Results: Patients had an average of 5 sclerotherapy treatments for HHT. Patients were treated using topical and/or local anesthesia with no reports of discomfort. Bleeding requiring intervention did not occur during the procedures. After the procedure all patients (100%) reported significantly less frequent and less severe nasal bleeding. A total of 83% reported that their need for nasal packing was reduced. All patients were willing to undergo the same treatment again. No complications such as perforation, crusting, or foul smell were reported.Conclusion: This is the first clinical experience demonstrating that office-based sclerotherapy with STS is a safe, tolerable, and useful alternative for the treatment of epistaxis due to HHT. (C) 2011 ARS-AAOA, LLC.

Background: Hypoglossal nerve stimulation has been demonstrated to relieve upper airway obstruction acutely, but its effect on obstructive sleep apnea is not known.Objective: To determine the response in obstructive sleep apnea to electrical stimulation of the hypoglossal nerve.Methods: Eight patients with obstructive sleep apnea were implanted with a device that stimulated the hypoglossal nerve unilaterally during inspiration. Sleep and breathing patterns were examined at baseline before implantation and after implantation at 1, 3, and 6 months and last follow-up.Results: Unilateral hypoglossal nerve stimulation decreased the severity of obstructive sleep apnea throughout the entire study period. Specifically, stimulation significantly reduced the mean apnea-hypopnea indices in non-rapid eye movement (mean +/- SD episodes per hour, 52.0 +/- 20.4 for baseline nights and 22.6 +/- 12.1 for stimulation nights; P<.001) and rapid eye movement (48.2 +/- 30.5 and 16.6 +/- 17.1, respectively; P<.001) sleep and reduced the severity of oxyhemoglobin desaturations. With improvement in sleep apnea, a trend toward deeper stages of non-rapid eye movement sleep was observed. Moreover, all patients tolerated long-term stimulation at night and did not experience any adverse effects from stimulation. Even after completing the study protocol, the 3 patients who remained free from stimulator malfunction continued to use this device as primary treatment.Conclusion: The findings demonstrate the feasibility and therapeutic potential for hypoglossal nerve stimulation in obstructive sleep apnea.

OBJECTIVES:The laryngeal chemoreflex is a reflexive central apnea, bradycardia, and cardiovascular collapse that occurs in young, maturing mammals in response to exposure of the laryngeal mucosa to acidic and/or organic stimuli. The severity of the laryngeal chemoreflex varies within a species from one animal to another, and in some animals, the response can be fatal. This study seeks to identify those factors that contribute to fatal laryngeal chemoreflex responses when the larynx is stimulated under normoxic conditions, and to define how the normoxic response differs from the hypoxic laryngeal chemoreflex response. STUDY DESIGN:This is a prospective study evaluating the response to laryngeal stimulation of 80 newborn piglets. METHODS:The laryngeal chemoreflex response was elicited from 67 piglets under normoxic conditions. The data were collected from a combination of three separate experimental protocols, each of which included inducing the laryngeal chemoreflex under normoxic conditions as the first step. The physiologic response was recorded with a combination of arterial blood gas, pulse oximetry, blood pressure, and continuous cardiac monitoring. RESULTS:Resumption of respirations occurred when the pCO(2) rose by a mean of 8.34 (Standard Deviation [SD] = 4.8) mmHg, regardless of response severity (ANOVA, P > .05). Moderate (requiring supplemental O(2) for recovery) and profound (fatal) responders had a significantly higher prestimulation pCO(2) (95% confidence interval [CI] 39.8-44.8 mmHg and 40.5-46.4 mmHg, respectively) than did mild (recovery without assistance) responders (95% CI 36.8-40.8 mmHg, ANOVA, P < .05). Baseline pH was statistically significantly different as a function of response severity (95% CI profound: 7.29-7.37, moderate: 7.33-7.38, and mild 7.36-7.39, P < .05). CONCLUSIONS:Accumulation of arterial CO(2) is associated with resumption of respirations during the normoxic laryngeal chemoreflex. The combination of an elevated prestimulation pCO(2) and a low prestimulation pH predicts a profound laryngeal chemoreflex response under normoxic conditions.