Introdução. A bronquiolite viral aguda é uma doença de evolução geralmente benigna, mas algumas crianças desenvolvem disfunção respiratória grave a ponto de requererem intubação e ventilação mecânica. Com a necessidade de intubação, surgem as eventuais complicações desta, sendo a estenose subglótica a mais grave. O objetivo desse trabalho é o de avaliar a incidência de estenose subglótica em crianças submetidas a intubação endotraqueal por bronquiolite viral aguda e seus possíveis fatores de risco. Métodos. Foram elegíveis todas as crianças internadas na Unidade de Terapia Intensiva Pediátrica do Hospital de Clínicas de Porto Alegre que necessitaram de intubação endotraqueal por mais de 24 horas. Foram excluídas crianças com história de intubação, patologia laríngea prévia, presença de traqueostomia atual ou no passado e pacientes considerados terminais pela equipe assistente. As crianças foram acompanhadas diariamente e, após a extubação, foram submetidas a fibronasolaringoscopia. Na primeira avaliação foram divididas em dois grupos: Grupo NA - alterações laríngeas leves ou exame normal, Grupo AA - alterações laríngeas moderadas a graves. As crianças do Grupo NA que desenvolveram sintomas durante o acompanhamento pós-internação e todas as do Grupo AA foram submetidas a novo exame em 7-10 dias. Nessa segunda avaliação foram, então, classificadas em Grupo NC - sem alterações crônicas e ESG - com estenose subglótica. Resultados. Foram incluídas 58 crianças entre novembro de 2005 e agosto de 2008. A incidência de estenose subglótica foi de 10,34% (2,51 - 18,18%). Todas as crianças que desenvolveram estenose subglótica apresentaram exame com alterações moderadas a graves logo após a extubação. O número de dias intubado, o número de reintubações, o número de dias em que o tubo foi mobilizado e o número de dias com sedação extra não foram estatisticamente diferentes entre os dois grupos. As crianças que desenvolveram estenose subglótica, porém, necessitaram de mais doses de sedação extra do que aquelas que não desenvolveram. Conclusão. Encontramos uma incidência de estenose subglótica de quase 11%. A necessidade de doses extras de sedação, possivelmente associada ao nível de agitação do paciente durante o período de intubação, parece ser um fato crucial para o desenvolvimento de estenose subglótica. / Introduction. Acute viral bronchiolitis is usually benign, but some children develop severe respiratory failure and require intubation and mechanical ventilation. Intubation may cause complications, of which subglottic stenosis is the most severe. The objective is to evaluate the incidence and risk factors of subglottic stenosis in children who underwent endotracheal intubation because of acute viral bronchiolitis. Methods. Children in the Pediatric Intensive Care Unit (PICU) of Hospital de Clínicas de Porto Alegre were eligible if they had endotracheal intubation for a period longer than 24 hours. Children were excluded if they had a history of intubation, previous laryngeal disease, current or past tracheostomy, or were classified as terminal by the healthcare team. Children were followed up daily and underwent flexible fiber-optic nasolaryngoscopy after extubation. In the first evaluation they were divided into two groups: NA group - mild laryngeal alterations or normal findings; AA group - moderate to severe laryngeal alterations. Children in the NA group developed symptoms during follow-up after PICU discharge, and all children in the AA group underwent another laryngoscopy 7-10 days later. After this second exam, children were classified into two other groups: NC - no chronic changes; and SGS - subglottic stenosis. Results: Fifty-eight children were included in the study from November 2005 to August 2008. The incidence of subglottic stenosis was 10.34% (2,51-18,18%). All children who developed subglottic stenosis had moderate to severe alterations immediately after extubation. The number of intubation days, tube reinsertions, days when tube maintenance was performed, and days with extra sedation were not statistically different between groups. Children that developed subglottic stenosis, however, had needed extra doses of sedation. Conclusion: We found a subglottic stenosis incidence of almost 11%. Extra doses of sedation, probably in association with patient agitation during intubation, seemed to be a crucial factor in the development of subglottic stenosis.

There are many conditions and diseases that affect voice production. One of these, subglottic stenosis (SGS), is characterized by a narrowing of the trachea near the cricotracheal junction. SGS causes dyspnea (labored breathing) and frequently surgery is necessary to eliminate the airway obstruction. SGS is also believed to adversely affect voice quality. While significant research has been conducted to study the effect of SGS on breathing, relatively few studies concerning its effect on voice production have been performed. The purpose of this research was to provide quantitative results concerning the predicted effects of SGS on vocal fold (VF) vibration and resulting sound production, and to provide tools for more extensive research involving synthetic VF models in the future. This was achieved through an experimental procedure in which a device simulating SGS was coupled with synthetic VF models and acoustic, aerodynamic, and vibratory measurements were acquired. Additionally, a device was developed and tested to study the effects of VF posturing using synthetic VF models. The design of the device is anticipated to serve as a useful tool in future experiments.The device simulating SGS was capable of creating an artificial stenosis of adjustable severity. The device was designed so that synthetic VF models inserted into rigid plates could be placed on top of the device, downstream of the stenosis. An experiment was conducted with the SGS device in conjunction with synthetic four-layer VF models in which flow and pressure were measured, radiated sound data were recorded, and visual data from a high-speed camera were captured as the percent obstruction was changed. The effects of subglottic stenosis were quantified using metrics such as onset pressure, glottal area, smoothed cepstral peak prominence (CPPS), harmonic-to-noise ratio (HNR), acoustic spectra, air flow, and pressure below and above the stenosis. The results show that the glottal area was not noticeably affected by the stenosis until 80% or 90% obstruction, and flow resistance through the stenosis was not significantly affected until 85% obstruction. However, changes in acoustics occurred as low as 65% or 70% obstruction.An MRI-compatible posturing device was developed which was capable of causing abduction/adduction and elongation in synthetic VF models. The device was used to adduct synthetic VF models from an abducted position into a pre-determined final phonatory posture as high-speed video and pressure data were collected. The device adducted to final phonatory posture in 500 ms, and phonation was initiated 680 ms later. In addition, the elongation of the synthetic models was varied as high-speed data were collected. The frequency of vibration of the four-layer models was found to not vary significantly when the models were elongated.

The voice plays a vital role in human communication. The purpose of voice research is to advance the understanding of voice production physics, with the ultimate goal of leading to improved voice care. In this research computational and synthetic vocal fold models were used to explore the role of subglottal geometry in vocal fold vibration. Three specific studies were performed. First, the effect of the inferior vocal fold surface angle on voice production was investigated using a two-dimensional self-oscillating finite element vocal fold model. Varying the inferior angle resulted in significant changes to model vibratory motion, glottal width, flow rate, and energy transfer. The changes were attributed primarily to changes in structural, rather than aerodynamic, factors. Second, subglottic stenosis (SGS) was introduced and parametrically varied in a similar computational model to determine the influence of SGS on vocal fold vibration. High severities of SGS influenced several factors related to vibration, including glottal width, flow rate, flow resistance, and vibration frequency. Subglottal pressure distributions and flow patterns were also affected. Third, the response of a self-oscillating silicone vocal fold model to varying degrees of SGS in an experimental setup was studied. Consistent with the computational SGS study, SGS had an effect on the synthetic model response at high severities. Changes were seen particularly in subglottal pressure and radiated acoustic sound, and consequently glottal efficiency, which may have important implications regarding the effect of SGS on the human voice.

Subglottic stenosis (SGS) is an abnormal narrowing of the airway at the level of the cricoid cartilage, above the first tracheal ring and immediately beneath the vocal folds. Individuals with SGS experience a reduction in their ability to breathe as well as adverse effects on voice function. SGS can result from a variety of causes with the type of treatment depending on stenosis severity. Surgical techniques such as laryngotracheal and cricotracheal reconstruction are beneficial for airway maintenance; however, these procedures have resulted in negative effects on voice production. On the other hand, there are patients with SGS who do not require surgery and still experience voice problems. The purpose of this study was to quantify the effects of SGS on vocal fold vibration using an excised larynx benchtop mechanical model. Using a within-subjects repeated measures design, nine porcine larynges underwent experimental conditions including 0% (i.e., normal airway), 50% and 75% stenosed. The primary outcome measure was phonation threshold flow (PTF), which is the rate of flow observed at the onset of phonation. For all larynges, the normal and stenosed conditions were sampled three times each and averaged. Analysis of the results revealed no statistically significant differences in PTF; however, descriptive data showed decreases in PTF and increased variability in PTF values as percent stenosis increased. These findings lay important groundwork for future research in SGS, specifically those that employ ex vivo methodologies. PTF has emerged as a promising means of quantifying voice function in addition to the traditional onset pressure measures. Future studies should examine a broader range of stenosis conditions with a larger sample size to promote generalization to clinical populations including individuals with SGS.

Subglottic stenosis (SGS) is a narrowing of the airway below the vocal folds and above the trachea. This narrowing may be idiopathic or caused by scarring in the airway due to prolonged endotracheal intubation, radiation therapy, trauma, or gastroesophageal reflux disease. People who present with SGS often experience respiratory difficulty both at rest and during exertion. Breathing difficulty increases with stenosis severity. SGS is also associated with voice problems. Research has identified relationships among stenosis severity, voice function and certain types of surgical management; however, many aspects of these relationships are not fully understood due to the complexities of studying human phonation in this population. The purpose of the present study was to examine the effects of SGS on aerodynamic features of voice function using an excised larynx benchtop mechanical model. Specifically, this research involved the comparison of excised porcine vocal fold vibration at baseline and under experimental conditions of 50% and 75% stenosed. The dependent variable was phonation threshold pressure (PTP), the minimum pressure needed to initiate and maintain vocal fold vibration. PTP was analyzed for nine excised porcine larynges, sampled three times each, at baseline and the two stenosis conditions. The results of this study revealed no differences in PTP based on within-subjects comparisons. Because airflow changes with airway narrowing, this finding might indicate that other factors are responsible for the voice problems associated with SGS that were not accounted for in the current mechanical model. Vocal fold tone is not easily simulated in a benchtop setup and might be an important consideration for future studies. The quantification and manipulation of vocal fold adduction, as well as the study of high-speed imaging, could be useful in future work involving excised larynx mechanical models for the study of SGS. The results from this pilot work represent an important step toward optimizing the experimental setup for studying aerodynamic features of SGS.