Laryngeal development and congenital lesions

Reproducing severe acute subglottic stenosis in a rabbit model

OBJECTIVES

The objectives of this study were to develop an animal model with consistent, severe subglottic stenosis (SGS), and to develop the timeline needed for intervention to limit rabbit mortality.

METHODS

Subglottic stenosis was created endoscopically using either a nylon or polypropylene brush in sixteen New Zealand White rabbits. The subglottic cross-sectional area was measured endoscopically using a right-angled probe and an open source image analysis software The cross-sectional areas of the stenotic and native airways were compared to calculate the subglottic stenosis percentage and Myer-Cotton grade classification.

RESULTS

The average diameter of the native subglottis was 4.7 mm (SD 0.4). The mean subglottic stenosis percentage was 73% (SD 32) for all rabbits. The three rabbits injured with the nylon brush had 30, 52, and 76% stenosis. Nine of the 12 surviving rabbits (75%) injured with the polypropylene brush had a >86% subglottic stenosis. Four rabbits in the polypropylene brush cohort died from procedural complications.

CONCLUSION

This study demonstrates a reliable model using a polypropylene brush to create severe acute subglottic stenosis. Cartilage exposure after creating the injury was associated with more severe stenosis. Mortality rate may have been reduced if endoscopic balloon dilation was performed electively seven days after injury, rather than emergently nine days after injury.

LEVEL OF EVIDENCE

4.

Histopathological effect of balloon dilation in a live rabbit: Implications for the pediatric airway

OBJECTIVE/HYPOTHESIS

To examine the short- and long-term histopathologic changes that occur in the subglottis in response to airway balloon dilation (ABD) with different balloon diameters and inflation pressures.

STUDY DESIGN

Prospective animal study using forty-two 8-month old New Zealand white rabbits at an academic animal research facility.

METHODS

Thirty-nine live New Zealand rabbits underwent a single ABD with diameters ranging from 6.0 mm to 10.0 mm and with pressures between 5.0 atmospheres (atm) to 15.0 atm. Animals were euthanized on postoperative days (POD) 1, 7, and 30, and the histopathological changes of the subglottis were examined. Three rabbits served as controls and underwent no ABD.

RESULTS

The subglottic airway diameter of all specimens measured 5.4 mm. When examining the fracture rate by balloon diameter, we found the following: 0 of 6 (0%) at 6 mm, 0 of 9 (0%) at 7 mm, 6 of 9 (67%) at 8 mm, 8 of 9 (89%) at 9 mm, and 6 of 6 (100%) at 10 mm. There was a statistically significant relationship with the rate of cricoid fracture as balloon diameter increased (P < .0001). All fractures occurred at the anterior cricoid lamina. On POD 1, we found mild ulceration in 5 of 6 (83%) using a 6-mm or 7-mm balloon and in 0 of 6 (0%) using an 8-mm, 9-mm, or 10-mm balloon; and moderate/severe ulceration in 1 of 6 (16.67%) using a 6-mm or 7-mm balloon and in 11 of 11 (100%) using an 8-mm, 9-mm, or 10-mm balloon (P < .0001). Also on POD 1, we found mild edema in 6 of 6 (100%) using a 6-mm or 7-mm balloon and in 5 of 11 (45%) using an 8-mm, 9-mm, or 10-mm balloon; and moderate/severe edema in 0 of 6 (0%) using a 6-mm/7-mm balloon and in 6 of 11 (55%) using an 8-mm, 9-mm, or 10-mm balloon (P =.048). On POD 7, we found fibroplasia in 5 of 6 (83%) using a 6-mm or 7-mm balloon and in 1 of 7 (14%) using an 8-mm, 9-mm, or 10-mm balloon; and moderate/severe fibroplasia in 1 of 6 (17%) using a 6-mm or 7-mm balloon and in 6 of 7 (86%) using an 8-mm, 9-mm, or 10-mm balloon (P =.029). Also on POD7, we found granulation tissue in 0 of 6 (0%) using a 6-mm or 7-mm balloon and in 5 of 7 (71%) using an 8-mm, 9-mm, or 10-mm balloon (P = .021). On POD 30, we found no fibrosis in 0 of 3 (0%) using a 7-mm balloon, mild fibrosis in 1 of 6 (16.67%), and moderate/severe fibrosis in 5 of 6 (83%) using an 8-mm or 9-mm balloon (P = .048). Also on POD 30, we found the mean subglottic cross-sectional luminal area was 23.79 mm(2) with a 7-mm balloon and 29.28 mm(2) with an 8-mm or 9-mm balloon (P = .019). Inflation pressure alone had no correlation with mucosal injury or probability of cricoid fracture.

CONCLUSIONS

Airway balloon dilation with balloon diameters that exceeded the airway diameter by 2.6 mm was associated with cricoid fractures. All cricoid fractures localized to the anterior cricoid lamina. Balloon diameters larger than the airway diameter by 2.6 mm resulted in a larger subglottic cross-sectional luminal area on POD 30. Airway balloon dilation with balloon diameters that could generate a cricoid fracture created more mucosal injury on POD 0, 1, and 7 than smaller balloon diameters. The histopathological effects of airway balloon dilation observed on POD 0, 1, and 7 resolved by POD 30. When balloon diameter is kept constant, inflation pressure alone had no correlation with mucosal injury or probability of cricoid fracture.

LEVEL OF EVIDENCE

NA (animal study). Laryngoscope, 125:S1-S11, 2015.

Objective assessment of supraglottoplasty outcomes using polysomnography

OBJECTIVE

Supraglottoplasty is well documented as an effective procedure in the management of moderate to severe laryngomalacia. Traditionally assessed outcomes in the treatment of laryngomalacia include: reduced stridor, improved feeding and a resumption of weight-gain. Previous authors have documented the use of polysomnography in assessing the severity of paediatric laryngeal abnormalities. The aim of the current study was to objectively assess the efficacy of supraglottoplasty for laryngomalacia by comparing data from pre- and post-operative polysomnography.

METHODS

A retrospective review was performed of patients undergoing supraglottoplasty for laryngomalacia at a tertiary referral paediatric hospital over a 35-month period. Patients were required to have undergone full overnight polysomnography both before and after supraglottoplasty. Pre- and post-operative polysomnographic results were compared and the statistical significance between mean values was determined.

RESULTS

From a total of 46 patients, 10 were suitable for inclusion into the study. Mean age at first presentation was 2 months and 19 days (range 30-134 days). The surgical procedure performed was bilateral division of aryepiglottic folds alone in 1 patient (1/10), bilateral division of aryepiglottic folds and bilateral trimming of arytenoid mucosa in 5 patients (5/10) and bilateral aryepiglottic fold division, bilateral arytenoid mucosal trimming and epiglottic trimming or epiglottopexy in 4 patients (4/10). Statistically significant improvements occurred in mean values for Total Sleep Time (TST) (P=0.049), Lowest Oxygen Saturation Levels (SpO2 nadir) (P=0.006), Obstructive Apnoea Hypopnoea Index (OAHI) (P=0.009) and Respiratory Disturbance Index (RDI) (P=0.002), following supraglottoplasty. An improvement in mean Transcutaneous Carbon Dioxide (TcCO2) value occurred, but did not achieve statistical significance (57.1 vs. 52.8) (P=0.259). The mean age at which post-operative polysomnography confirmed a reversal of abnormal respiratory parameters following surgery was 5 months and 18 days.

CONCLUSIONS

Polysomnography is an effective method for objectively assessing the efficacy of supraglottoplasty for laryngomalacia. Supraglottoplasty effectively reverses the abnormal respiratory parameters occurring in moderate to severe laryngomalacia.

Supraglottoplasty for laryngomalacia with obstructive sleep apnea

OBJECTIVES/HYPOTHESIS

To determine if supraglottoplasty (SGP) is effective in reversing abnormal respiratory parameters in children with laryngomalacia and obstructive sleep apnea (OSA).

STUDY DESIGN

Retrospective case series at a tertiary referral children's hospital.

METHODS

Ten patients with laryngomalacia and OSA as documented by polysomnography underwent SGP between 2005 and 2007. Data collected included age, findings on flexible and rigid endoscopy, type of procedure performed, and postoperative course. The postoperative polysomnographies were reviewed to identify changes in obstructive apnea index, obstructive apnea/hypopnea index, respiratory disturbance index, and low arterial oxygen saturation (O2 nadir) after SGP.

RESULTS

All 10 patients were successfully extubated after SGP. There were no peri- or postoperative complications, and no patient required a subsequent airway procedure. Each patient had a postoperative nocturnal polysomnography performed after SGP at 11 weeks (range 2-29 weeks). Caregivers reported mild improvement (10%), significant improvement (70%), and complete resolution (20%) of stridor and nocturnal snoring at a follow-up visit 4 weeks after discharge. Marked improvements were observed in obstructive apnea index, obstructive apnea/hypopnea index, respiratory disturbance index and O2 nadir, all of which were statistically significant (P < .05).

CONCLUSIONS

Polysomnography should be considered in the initial evaluation of infants with moderate laryngomalacia to rule out OSA. SGP is an effective treatment for infants with laryngomalacia and OSA. The significant benefits of the procedure outweigh thelow morbidity. Improvement after surgery was reliably confirmed by polysomnography in this study.

Chronic stridor caused by laryngomalacia in children: work of breathing and effects of noninvasive ventilatory assistance

Breathing pattern, gas exchange, and respiratory effort were assessed in five awake children with chronic stridor caused by laryngomalacia during spontaneous breathing (SB) and noninvasive mechanical ventilation (NIMV). During SB, the youngest children were able to maintain normal gas exchange at the expense of an increased work of breathing as assessed by calculated diaphragmatic pressure-time product (PTPdi), whereas the opposite was observed in the older children. NIMV increased tidal volume, from 8.77 +/- 2.04 ml/kg during SB to 11.67 +/- 2.52 ml/kg during NIMV, p = 0.04, and decreased respiratory rate, from 24.4 +/- 5.6 breaths/ min during SB to 16.6 +/- 0.9 breaths/min during NIMV, p = 0.04. NIMV unloaded the respiratory muscles as reflected by the significant reduction in PTPdi, from a mean value of 541.0 +/- 196.6 cm H(2)O x s x min(-1) during SB to 214.8 +/- 116.0 cm H(2)O x s x min(-1) during NIMV, p = 0.04. Therefore, NIMV successfully relieves the additional load imposed on the respiratory muscles. Long-term home NIMV was provided to a total of 12 children with laryngomalacia (including these five) and was associated with clinical improvement in sleep and growth.

Neonatal subglottic stenosis--incidence and trends

OBJECTIVE/HYPOTHESIS

Neonatal subglottic stenosis is a known entity arising from endotracheal tube intubation. In the 1970s and 1980s, estimates of the incidence of subglottic stenosis were in the range of 0.9% to 8.3% of intubated neonates. Because of improved techniques of handling neonates who require ventilatory support, we thought the actual incidence of neonatal subglottic stenosis in the late 1990s was much lower.

STUDY DESIGN

We retrospectively reviewed all neonatal intensive-care unit (NICU) admissions from 1997 at our institution, which serves as a level 3 NICU. We also performed a MEDLINE search of the reported incidence of neonatal subglottic stenosis between 1960 and 1999.

METHODS

Analysis was performed to identify all children who developed subglottic stenosis at our institution. Data were also collected and analyzed with regard to average gestational age, average birth weight, average duration of intubation, and the number of children requiring tracheostomy. The reports identified in the literature were reviewed as to the incidence of subglottic stenosis.

RESULTS

A total of 544 neonates were admitted to the unit. Of these, 281 were intubated for an average of 11 days. No patients developed subglottic stenosis. Three patients required tracheostomies for other reasons. All studies published after 1983 reported an incidence of neonatal subglottic stenosis as less than 4.0%, and all studies published after 1990 reported an incidence of neonatal subglottic stenosis as less than 0.63%.

CONCLUSIONS

Although our report applies to only a single institution in a single year, after reviewing the literature we think a downward trend exists in the incidence of neonatal subglottic stenosis in the late 1990s. The current incidence of neonatal subglottic stenosis is likely between 0.0% and 2.0%.

Severe laryngomalacia: surgical indications and results in 115 patients

Between 1987 and 1993, 115 children were operated on for severe forms of laryngomalacia in two pediatric ear, nose, and throat (ENT) departments. The criteria used to determine the severity of the illness were selected following short hospitalization periods during which the children received both pediatric and ENT checkups. Based on clinical manifestations and/or the results of pH monitoring gastroesophageal reflux was found to be present in 68% of the children in the study. Detailed analysis and endoscopy were used to differentiate the symptoms that were related to laryngomalacia from those that were caused by other conditions, including mixed-breathing, swallowing, and sucking difficulties. Endoscopic resection of the aryepiglottic folds, with or without the use of a carbon dioxide laser, resulted in rapid improvement of both ventilation and swallowing. The success rate of this simple and effective procedure, which has no inherent morbidity, was 98% in an average follow-up period of 30 months. Only seven children required an additional similar procedure. The procedure failed in only two children, who needed to be tracheotomized. Given these excellent results, endoscopic resection can be considered an effective technique for the management of severe laryngomalacia.

Congenital subglottic stenosis: the elliptical cricoid cartilage

Various malformations of the cricoid cartilage produce congenital subglottic stenosis. The elliptical cricoid cartilage first was demonstrated histopathologically in horizontal sections of six postmortem specimens and now has been identified clinically in ten patients. The clinical diagnosis of the elliptical cricoid cartilage, suggested by anteroposterior soft tissue neck films, is confirmed at direct laryngoscopy. Delineation of the precise location, extent, and histopathology of subglottic stenosis provides the basis for rational management.

Laryngeal surgery in the pediatric patient

The primary concern in laryngeal surgery in the infant and child is to relieve airway obstruction, rather than phonation. Because airway obstruction above the larynx may stimulate or be confused with laryngeal pathology, these are described as the signs and symptoms of laryngeal disease. Although tracheotomy in the infant is frequently said to be a cause of a long-term problem, the procedure can be carried out in the smallest premature quite safely and without an extubation problem. The author's method of performing the operation is described. Most laryngeal surgery in the child is performed by the endoscopic approach, special scopes being used for special purposes. In addition to conventional instrumentation the cryoprobe and CO2 laser and employed. The author's method of treating glottic and subglottic stenosis is outlined.