Conundrums in the breathless athlete; exercise-induced laryngeal obstruction or asthma?

PURPOSE: Exercise-induced bronchoconstriction (EIB) and exercise-induced laryngeal obstruction (EILO) are the two disorders commonly considered when athletes complain of exertional dyspnea. They are highly different but often confused. We aimed to address this diagnostic challenge and its consequences in elite athletes. METHODS: We included all athletes competing at national or international level, referred to our institution for workup for EILO during 2013-2016. We diagnosed EILO from video-recorded laryngoscopy performed during maximal cardiopulmonary treadmill exercise (CLE test). Symptoms and previous diagnostic evaluations were obtained from referral letters and chart reviews. RESULTS: Exercise-induced laryngeal obstruction was diagnosed in 73/101 referred athletes, of whom 70/73 had moderate/severe supraglottic obstruction and 3/73 had primarily glottic obstruction with only minor supraglottic involvement. Of the 73 athletes with EILO, we were able to identify objective tests for asthma in 55 participants, of whom 22 had findings supporting asthma. However, 58/73 had used asthma therapy at some time previously, with current use in 28. Only three reported that asthma medication had improved their exercise-related breathing problems, two of whom with tests confirming asthma. Treatment for EILO improved breathing problems in all but four. CONCLUSIONS: Objective testing verified EILO in most of the referred athletes. EILO coexisting with asthma was common, and large proportions had used asthma medication; however, few reported effect on exercise-related breathing problems. Unexplained persistent exertional dyspnea must not lead to indiscriminate escalation of asthma treatment, but instead incite investigation for EILO, either as a co-morbidity or as a differential diagnosis.

Clinical responses following inspiratory muscle training in exercise-induced laryngeal obstruction.

PURPOSE: Exercise-induced laryngeal obstruction (EILO) is relatively common in young people. Treatment rests on poor evidence; however, inspiratory muscle training (IMT) has been proposed a promising strategy. We aimed to assess laryngeal outcomes shortly after IMT, and to compare self-reported symptoms with a control group 4-6 years later. METHODS: Two groups were retrospectively identified from the EILO-register at Haukeland University Hospital, Norway; one group had received only information and breathing advice (IBA), and another additionally IMT (IBA + IMT). At diagnosis, all participants performed continuous laryngoscopy during exercise (CLE), with findings split by glottic and supraglottic scores, and completed a questionnaire mapping exercise-related symptoms. After 2-4 weeks, the IBA + IMT-group was re-evaluated with CLE-test. After 4-6 years, both groups were re-assessed with a questionnaire. RESULTS: We identified 116 eligible patients from the EILO-register. Response rates after 4-6 years were 23/58 (40%) and 32/58 (55%) in the IBA and IBA + IMT-group, respectively. At diagnosis, both groups rated symptoms similarly, but laryngeal scores were higher in the IBA + IMT-group (P = 0.003). After 2-4 weeks, 23/32 in the IBA + IMT-group reported symptom improvements, associated with a decrease of mainly glottic scores (1.7-0.3; P < 0.001), contrasting unchanged scores in the 9/32 without symptom improvements. After 4-6 years, exercise-related symptoms and activity levels had decreased to similar levels in both groups, with no added benefit from IMT; however, full symptom resolution was reported by only 8/55 participants. CONCLUSION: Self-reported EILO symptoms had improved after 4-6 years, irrespective of initial treatment. Full symptom resolution was rare, suggesting individual follow-up should be offered.

Laryngeal response patterns influence the efficacy of mechanical assisted cough in amyotrophic lateral sclerosis.

BACKGROUND: Most patients with amyotrophic lateral sclerosis (ALS) are treated with mechanical insufflation-exsufflation (MI-E) in order to improve cough. This method often fails in ALS with bulbar involvement, allegedly due to upper-airway malfunction. We have studied this phenomenon in detail with laryngoscopy to unravel information that could lead to better treatment. METHODS: We conducted a cross-sectional study of 20 patients with ALS and 20 healthy age-matched and sex-matched volunteers. We used video-recorded flexible transnasal fibre-optic laryngoscopy during MI-E undertaken according to a standardised protocol, applying pressures of ±20 to ±50 cm H2O. Laryngeal movements were assessed from video files. ALS type and characteristics of upper and lower motor neuron symptoms were determined. RESULTS: At the supraglottic level, all patients with ALS and bulbar symptoms (n=14) adducted their laryngeal structures during insufflation. At the glottic level, initial abduction followed by subsequent adduction was observed in all patients with ALS during insufflation and exsufflation. Hypopharyngeal constriction during exsufflation was observed in all subjects, most prominently in patients with ALS and bulbar symptoms. Healthy subjects and patients with ALS and no bulbar symptoms (n=6) coordinated their cough well during MI-E. CONCLUSIONS: Laryngoscopy during ongoing MI-E in patients with ALS and bulbar symptoms revealed laryngeal adduction especially during insufflation but also during exsufflation, thereby severely compromising the size of the laryngeal inlet in some patients. Individually customised settings can prevent this and thereby improve and extend the use of non-invasive MI-E.

Inducible laryngeal obstruction: an official joint European Respiratory Society and European Laryngological Society statement.

Inducible laryngeal obstruction (ILO) describes an inappropriate, transient, reversible narrowing of the larynx in response to external triggers. ILO is an important cause of a variety of respiratory symptoms and can mimic asthma. Current understanding of ILO has been hampered by imprecise nomenclature and variable approaches to assessment and management. A task force of the European Respiratory Society (ERS) and European Laryngological Society (ELS) was thus set up to address this, and to identify research priorities.A literature search identified relevant articles published until June 2016, using all identifiable terms for ILO, although including only articles using laryngoscopy. In total, 172 out of 252 articles met the inclusion criteria, summarised in sections on diagnostic approach, aetiology, comorbidities, epidemiology and treatment. The consensus taxonomy published by ERS, ELS and the American College of Chest Physicians (ACCP) in 2015 is used throughout this statement.We highlight the high prevalence of ILO and the clinical impact for those affected. Despite recent advances, most aspects of this condition unfortunately remain incompletely understood, precluding firm guidance. Specifically, validated diagnostic and treatment algorithms are yet to be established, and no randomised control studies were identified in this search; hence we also make recommendations for future research.

Exercise inducible laryngeal obstruction: diagnostics and management.

Obstruction of the central airways is an important cause of exercise-induced inspiratory symptoms (EIIS) in young and otherwise healthy individuals. This is a large, heterogeneous and vastly understudied group of patients. The symptoms are too often confused with those of asthma. Laryngoscopy performed as symptoms evolve during increasing exercise is pivotal, since the larynx plays an important role in symptomatology for the majority. Abnormalities vary between patients, and laryngoscopic findings are important for correct treatment and handling. The simplistic view that all EIIS is due to vocal cord dysfunction [VCD] still hampers science and patient management. Causal mechanisms are poorly understood. Most treatment options are based on weak evidence, but most patients seem to benefit from individualised information and guidance. The place of surgery has not been settled, but supraglottoplasty may cure well-defined severe cases. A systematic clinical approach, more and better research and randomised controlled treatment trials are of utmost importance in this field of respiratory medicine.

Impact of EMG Changes in Continuous Vagal Nerve Monitoring in High-Risk Endocrine Neck Surgery.

BACKGROUND: Continuous vagal intraoperative neuromonitoring (CIONM) of the recurrent laryngeal nerve (RLN) may reduce the risk of RLN lesions during high-risk endocrine neck surgery such as operation for large goiter potentially requiring transsternal surgery, advanced thyroid cancer, and recurrence. METHODS: Fifty-five consecutive patients (41 female, median age 61 years, 87 nerves at risk) underwent high-risk endocrine neck surgery. CIONM was performed using the commercially available NIM-Response 3.0 nerve monitoring system with automatic periodic stimulation (APS) and matching endotracheal tube electrodes (Medtronic Inc.). All CIONM events (decreased amplitude/increased latency) were recorded. RESULTS: APS malfunction occurred on three sides (3%). A total of 138 CIONM events were registered on 61 sides. Of 138, 47 (34%) events were assessed as imminent (13 events) or potentially imminent (34 events) lesions, whereas 91 (66%) were classified as artifacts. Loss of signal was observed in seven patients. Actions to restore the CIONM baseline were undertaken in 58/138 (42%) events with a median 60 s required per action. Four RLN palsies (3 transient, 1 permanent) occurred: one in case of CIONM malfunction, two sudden without any significant previous CIONM event, and one without any CIONM event. The APS vagus electrode led to temporary damage to the vagus nerve in two patients. CONCLUSIONS: CIONM may prevent RLN palsies by timely recognition of imminent nerve lesions. In high-risk endocrine neck surgery, CIONM may, however, be limited in its utility by system malfunction, direct harm to the vagus nerve, and particularly, inability to indicate RLN lesions ahead in time.

Comparison between two assessment methods for exercise-induced laryngeal obstructions.

Exercise-induced laryngeal obstructions (E-ILOs) are important differential diagnoses to exercise-induced asthma and are diagnosed by the continuous laryngoscopy exercise (CLE) test. There are two different methods for evaluating the severity of E-ILOs using recordings from the CLE test; the CLE score and EILOMEA. The aim of this study was to investigate the consistency between these methods. Using their respective method, the developers of each method evaluated 60 laryngoscopic recordings from patients with different subtypes and various levels of severity of E-ILOs. The CLE score evaluates glottic and supraglottic obstructions on a 4-grade scale. EILOMEA uses software to calculate the obstruction severity on continuous scales from a still frame of the larynx during maximal obstruction giving three parameters reflecting glottic and supraglottic obstruction. The means of the EILOMEA measures differed significantly for CLE score 1 vs. 2 and 2 vs. 3, but not for 0 vs. 1 for glottic as well as supraglottic obstructions. The EILOMEA method does not distinguish between CLE score 0 and 1, but otherwise the methods correlate. Since previous studies have suggested that only CLE scores of 2 and 3 reflect a severity of E-ILOs of clinical importance, this lack of the EILOMEA method is not crucial for a correct medical evaluation.

The Norwegian Voice Handicap Index (VHI-N) patient scores are dependent on voice-related disease group.

The aim of this study is to determine to what extent the Voice Handicap Index-Norwegian (VHI-N) is scored depending on specific laryngological disease. In a multi-center study, 126 healthy subjects and 355 patients with different voice-related diseases answered the VHI-N. The VHI-N scores showed high Cronbach's alpha. Analyses of variance were performed with VHI-N dependent and specific voice-related disease as independent variable, and showed highly significant dependence by group allocation (F(7,461) = 28.0; p < 0.001). When studying post hoc analyses secondary to this ANOVA analysis, we have shown that the control group scored lower than the entire patient groups (all p < 0.001) except the dysplasia group. Aphonic patients scored higher than all the other groups (all p < 0.001) except those with spasmodic dysphonia. The cancer patient group furthermore scored lower than patient groups with recurrent palsy, dysfunctional disease or spasmodic dysphonia (all p < 0.001). In addition, patients with recurrent palsy scored higher than patients with degenerative/inflammatory disease (p < 0.001). No influences of patient age, gender, or smoking were observed in the VHI-N scores. The VHI-N is a psychometrically well-functioning instrument, also at disease-specific levels and discriminates well between health and voice diseases, as well as between different voice-related diseases. The VHI-N may be recommended to be used when monitoring voice-related disease treatment.

Larynx during exercise: the unexplored bottleneck of the airways.

Exercise-induced shortness of breath is not uncommon in otherwise healthy young people. Based on the presenting symptoms alone, it is challenging to distinguish exercise-induced asthma (EIA) from exercise-induced obstruction of central airways, sometimes leading to diagnostic errors and inadequate treatment. Central airway obstruction usually presents with exercise-induced inspiratory symptoms (EIIS) during ongoing exercise. EIIS tends to peak towards the end of an exercise session or immediately after its completion, contradicting symptoms of EIA typically peaking 3-15 min after the exercise has stopped. EIIS is usually associated with some form of laryngeal obstruction. Transnasal flexible laryngoscopy performed continuously throughout an incremental exercise test from rest to exhaustion or to intolerable symptoms is usually diagnostic, and also provides information that is important for further handling and treatment. Reflecting the complex anatomy and functional features of the larynx, exercise-induced laryngeal obstruction (EILO) appears to be a heterogeneous condition. Contradicting previous beliefs, recent literature suggests that laryngeal adduction in a majority of cases starts in supraglottic structures and that vocal cord adduction (VCD) most often occurs as a secondary phenomenon. However, EILO is poorly understood and more and better research is needed to unravel causal mechanisms. The evidence base for treatment of EILO is weak. Speech therapy, psychotherapy, biofeedback, muscle training, anticholinergic aerosols have all been applied, as has laser supraglottoplasty. Randomized controlled trials with well-defined and verifiable inclusion and success criteria are required to establish evidence-based treatment schemes.

A speech therapy treatment protocol for exercise induced laryngeal obstruction.

Background: Exercise induced laryngeal obstruction (EILO) is a common cause of exertional breathing problems in young individuals, relevant to 5%-7% of young people. It is caused by paradoxical inspiratory adduction of laryngeal structures and diagnosed by continuous visualization of the larynx during high intensity exercise. Empirical data suggest that EILO consists of different subtypes that require different therapeutic approaches. Currently applied treatment approaches do not rest on randomized controlled trials (RCTs), and thus evidence-based guidelines cannot be established. This protocol describes the speech therapy treatment approach which is applied to EILO patients in a large prospective RCT called HelpILO. Methods and analysis: Consenting patients consecutively diagnosed with EILO at Haukeland University Hospital are randomized into four treatment arms. Speech therapy is represented in two of these, provided in a structured manner based on general speech therapy principles and abdominal breathing, combined with experience obtained with these patients at our hospital during the last decades. The main outcome measure of HelpILO is changes of laryngoscopically visualized laryngeal adduction, rated at peak exercise before vs. after interventions, using a validated scoring system. Ethics and dissemination: Despite widespread use of speech therapy in patients with EILO, this approach is insufficiently tested in RCTs, and the study is therefore considered ethically appropriate. The study will provide knowledge listed as a priority in a recent statement issued by major respiratory and laryngological societies and requested by clinicians and researchers engaged in this area. The results will be presented at relevant conferences, patient fora, and media platforms, and published in relevant peer reviewed international journals.

Cross-cultural adaption and translation of the voice handicap index into Norwegian.

AIMS: To examine the psychometric properties of a Norwegian translation of the Voice Handicap Index (VHI) and test its ability to discriminate between patients and controls. Abbreviated versions of VHI were also studied. METHOD: Following standard translation, 126 healthy subjects and 126 patients with laryngeal disease answered the Norwegian translation of the VHI-30 [hereafter, VHI-30(N)]. RESULTS: The VHI(N) showed a high Cronbach α. Control/patient scores were as follows: Emotional (E): 0.88/0.90; Functional (F): 0.77/0.91; Physical (P): 0.86/0.83, and total: 0.93/0.94. One three-level question where the subjects rated the level of voice disease correlated well with the VHI(N) scores. The 90th (95th) percentile of the control score was 18 (33), whereas the mean ± SEM patient score was 52.3 ± 2.04 of a maximum of 120 points. Differences between patient and control groups were significant for all questions on the VHI(N). Receiver operating characteristic analyses demonstrate that the F, P, E and total VHI scores discriminated very well between patients and controls. This was also the case when the abbreviated scales were analyzed as published by Nawka et al. [Folia Phoniatr Logop 2009;61:37-48] and Rosen et al. [Laryngoscope 2004;114:1549-1556]. CONCLUSION: This Norwegian version of the VHI questionnaire seems to be psychometrically sound.

Reliability of translaryngeal airway resistance measurements during maximal exercise.

Objective: Exercise-induced laryngeal obstruction is an important cause of exertional dyspnoea. The diagnosis rests on visual judgement of relative changes of the laryngeal inlet during continuous laryngoscopy exercise (CLE) tests, but we lack objective measures that reflect functional consequences. We aimed to investigate repeatability and normal values of translaryngeal airway resistance measured at maximal intensity exercise. Methods: 31 healthy nonsmokers without exercise-related breathing problems were recruited. Participants performed two CLE tests with verified positioning of two pressure sensors, one at the tip of the epiglottis (supraglottic) and one by the fifth tracheal ring (subglottic). Airway pressure and flow data were continuously collected breath-by-breath and used to calculate translaryngeal resistance at peak exercise. Laryngeal obstruction was assessed according to a standardised CLE score system. Results: Data from 26 participants (16 females) with two successful tests and equal CLE scores on both test sessions were included in the translaryngeal resistance repeatability analyses. The coefficient of repeatability (CR) was 0.62 cmH2O·L-1·s-1, corresponding to a CR% of 21%. Mean±sd translaryngeal airway resistance (cmH2O·L-1·s-1) in participants with no laryngeal obstruction (n=15) was 2.88±0.50 in females and 2.18±0.50 in males. Higher CLE scores correlated with higher translaryngeal resistance in females (r=0.81, p<0.001). Conclusions: This study establishes translaryngeal airway resistance obtained during exercise as a reliable parameter in respiratory medicine, opening the door for more informed treatment decisions and future research on the role of the larynx in health and disease.

Exercise-induced Laryngeal Obstruction: Protocol for a Randomized Controlled Treatment Trial.

BACKGROUND: Exercise-induced laryngeal obstruction (EILO) is a common cause of exertional breathing problems in young individuals, caused by paradoxical inspiratory adduction of laryngeal structures, and diagnosed by continuous visualization of the larynx during high-intensity exercise. Empirical data suggest that EILO consists of different subtypes, possibly requiring different therapeutic approaches. Currently applied treatments do not rest on randomized controlled trials, and international guidelines based on good evidence can therefore not be established. This study aims to provide evidence-based information on treatment schemes commonly applied in patients with EILO. METHODS AND ANALYSIS: Consenting patients consecutively diagnosed with EILO at Haukeland University Hospital will be randomized into four non-invasive treatment arms, based on promising reports from non-randomized studies: (A) standardized information and breathing advice only (IBA), (B) IBA plus inspiratory muscle training, (C) IBA plus speech therapy, and (D) IBA plus inspiratory muscle training and speech therapy. Differential effects in predefined EILO subtypes will be addressed. Patients failing the non-invasive approach and otherwise qualifying for surgical treatment by current department policy will be considered for randomization into (E) standard or (F) minimally invasive laser supraglottoplasty or (G) no surgery. Power calculations are based on the main outcomes, laryngeal adduction during peak exercise, rated by a validated scoring system before and after the interventions. ETHICS AND DISSEMINATION: The study will assess approaches to EILO treatments that despite widespread use, are insufficiently tested in structured, verifiable, randomized, controlled studies, and is therefore considered ethically sound. The study will provide knowledge listed as a priority in a recent statement issued by the European Respiratory Society, requested by clinicians and researchers engaged in this area, and relevant to 5-7% of young people. Dissemination will occur in peer-reviewed journals, at relevant media platforms and conferences, and by engaging with patient organizations and the healthcare bureaucracy.

Exercise-induced laryngeal obstruction: natural history and effect of surgical treatment.

The current follow-up study concerning the supraglottic type of exercise-induced laryngeal obstruction (EILO) was performed to reveal the natural history of supraglottic EILO and compare the symptoms, as well as the laryngeal function in conservatively versus surgically treated patients. A questionnaire-based survey was conducted 2-5 years after EILO was diagnosed by a continuous laryngoscopy exercise (CLE) test in 94 patients with a predominantly supraglottic obstruction. Seventy-one patients had been treated conservatively and 23 with laser supraglottoplasty. The questionnaire response rate was 70 and 100% in conservatively treated (CT) and surgically treated (ST) patients, respectively. A second CLE test was performed in 14 CT and 19 ST patients. A visual analogue scale on symptom severity indicated improvements in both the groups, i.e. mean values (± standard deviations) declined from 73 (20) to 53 (26) (P < 0.001) in the CT group and from 87 (26) to 25 (27) (P < 0.001) in the ST group. At follow-up, ST patients reported lower scores regarding current level of complaints, and higher ability to perform exercise, as well as to push themselves physically, all compared to CT patients (P < 0.001). CLE scores were normalized in 3 of 14 (21%) CT and 16 of 19 (84%) ST patients (Z = -3.6; P < 0.001). In conclusion, symptoms of EILO diagnosed in adolescents generally decreased during 2-5 years follow-up period but even more after the surgical treatment. Patients with supraglottic EILO may benefit from supraglottoplasty both as to laryngeal function and symptom relief.

Mononuclear phagocytes in head and neck squamous cell carcinoma.

The head and neck squamous cell carcinoma microenvironments contain many immune cells and their secretory products. Many of these cells belong to the mononuclear phagocyte system. The aim of this review is to study the interactions between mononuclear phagocytes and head and neck squamous cell carcinoma tissue. The role of inflammation in tumours and the cytokine interleukin-6 will be highlighted. Future therapy strategies in the treatment of head and neck cancer might be directed towards mononuclear phagocytes and their cytokine production.

Acoustic Voice Analysis and Maximum Phonation Time in Relation to Voice Handicap Index Score and Larynx Disease.

OBJECTIVES: Patients with voice-related disorders are ideally treated by a multidisciplinary team. Acoustic voice analysis and patient-reported outcome measures are recommended parts of the clinical assessment. The present paper aims at further documenting the importance of acoustic voice analyses, maximum phonation time (MPT) and Voice Handicap Index (VHI) into clinical investigations. STUDY DESIGN: The participants (N = 80 larynx cancer, N = 32 recurrent palsy, N = 23 dysfunctional, N = 75 degenerative/inflammation (N = 19 various excluded)) were included consecutively at the outpatient laryngology clinic at Haukeland University Hospital. In addition, a control group of 98 healthy subjects were included. METHOD: Voice samples, MPT, and the VHI scores in addition to standard clinical information were obtained. Acoustic analyses were performed from these samples determining level of jitter, shimmer and Noise-to-Harmonic ratio (NHR) as well as analyzing frequency of a prolonged vowel. RESULTS: Jitter, shimmer, and NHR scores correlated strongly (r ≈ 0.8; P < 0.001) to each other. By Analysis of Variance analyses, we have determined significant dependence on diagnostic group analyzing all the obtained acoustic scores (all P < 0.001). All patient groups but the dysfunctional group scored to some extent worse than the control group (mostly at P < 0.001). In addition, jitter scores from dysfunction group were lower than recurrent palsy group (P < 0.05) and shimmer scores were lower among dysfunctional than the cancer group (P < 0.05). Regarding NHR the cancer patients scored higher than the degenerative/inflammatory group (P < 0.05). The cancer group scored with longer MPT than the degenerative/inflammatory (P < 0.001) and recurrent palsy groups (P < 0.05). CONCLUSION: Among larynx disease patients acoustic and MPT analyses segregated with all determined analyses between patients and control conditions except the dysfunctional group, but also to some extent between various patient groups. VHI scores correlated to jitter, shimmer and NHR scores among cancer and degenerative/inflammatory disease patients. Acoustic analyses potentially add information useful to laryngological patient studies.

Long Waiting Times for Elective Hospital Care - Breaking the Vicious Circle by Abandoning Prioritisation.

BACKGROUND: Policies assigning low-priority patients treatment delays for care, in order to make room for patients of higher priority arriving later, are common in secondary healthcare services today. Alternatively, each new patient could be granted the first available appointment. We aimed to investigate whether prioritisation can be part of the reason why waiting times for care are often long, and to describe how departments can improve their waiting situation by changing away from prioritisation. METHODS: We used patient flow data from 2015 at the Department of Otorhinolaryngology, Haukeland University Hospital, Norway. In Dynaplan Smia, Dynaplan AS, dynamic simulations were used to compare how waiting time, size and shape of the waiting list, and capacity utilisation developed with and without prioritisation. Simulations were started from the actual waiting list at the beginning of 2015, and from an empty waiting list (simulating a new department with no initial patient backlog). RESULTS: From an empty waiting list and with capacity equal to demand, waiting times were built 7 times longer when prioritising than when not. Prioritisation also led to poor resource utilisation and short-lived effects of extra capacity. Departments where prioritisation is causing long waits can improve their situation by temporarily bringing capacity above demand and introducing "first come, first served" instead of prioritisation. CONCLUSION: A poor appointment allocation policy can build long waiting times, even when capacity is sufficient to meet demand. By bringing waiting times down and going away from prioritisation, the waiting list size and average waiting times at the studied department could be maintained almost 90% below the current level - without requiring permanent change in the capacity/demand ratio.

An experimental study on intraoperative recovery of recurrent laryngeal nerve function.

OBJECTIVE: If bilateral thyroid surgery is planned and staged thyroidectomy considered in case of loss of neuromonitoring signal (LOS), a waiting time of 20 minutes is suggested for evaluation of early nerve recovery. This recommendation is based on clinical observations and has not been thoroughly validated experimentally. METHODS: Sixteen pigs were randomly studied, and electromyogram (EMG) was continuously recorded during traction injury until an amplitude decrease of 70% from baseline (BL) (16 nerves) or LOS (16 nerves), and further during 40-minute recovery time. At the end of the experiments, vocal cord twitch was evaluated by video-laryngoscopy. RESULTS: In the 70% group, 8 of 16 nerves recovered to or above an amplitude of 50% of baseline after 20 minutes and finally one more after 40 minutes. In the LOS group, only one nerve showed recovery after 20 minutes and one more after 40 minutes. Video-laryngoscopy revealed good or strong vocal cord twitches, in 10 of 14 nerves in the 70% group and in only 2 of 14 nerves in the LOS group. CONCLUSIONS: The overall intraoperative recovery was low after LOS. Even after 70% amplitude depression, only half of the nerves showed recovery to amplitudes ≥50% of BL. Nerve recovery is dynamic, and a waiting time of 20 minutes seems appropriate for the identification of early nerve recovery before decisions are taken to continue or terminate surgery. The final EMG amplitude was not always well correlated with estimated vocal cord twitch, evaluated by video-laryngoscopy. This observation needs further investigation.

Vocal cord function during recurrent laryngeal nerve injury assessed by accelerometry and EMG.

OBJECTIVE: Gradual impairment of nerve conduction is expected to be tightly associated with simultaneous gradual loss of vocal cord contractility, related to the fact that injured axons are connected to a defined number of muscle cells. In clinical studies, there is a time gap between observed adverse electromyographic (EMG) changes and examination of vocal cord function. This study evaluates the impact of intraoperative EMG changes on synchronous vocal cord contractility by simultaneous use of continuous intraoperative neuromonitoring (C-IONM) and accelerometry for registration of actual vocal cord function at a given change of EMG amplitude. METHODS: EMG was obtained following vagus nerve stimulation by use of C-IONM. A vocal cord accelerometer probe that could be attached to the vocal cords was developed based on a LIS3DH ultra low-power high performance three axis linear accelerometer (STMicroelectronics, Geneva, Switzerland). Accelerometer data were registered continuously together with EMG data during traction injury of the recurrent laryngeal nerve (RLN) until an amplitude depression ≤100 µV. RESULTS: Six RLN from four immature domestic pigs were studied. Vocal cord contractility assessed by vocal cord accelerometry decreased in parallel with EMG amplitude, with significant correlations ranging from 0.707 to 0.968. CONCLUSION: Decrease of EMG amplitude during traction injury to the RLN injury is closely associated with a parallel drop in vocal cord contractility. LEVEL OF EVIDENCE: NA Laryngoscope, 130:1090-1096, 2020.