Outcomes



Fig. 1
Direct laryngoscopic view of laryngomalacia. Note the curled appearance of the epiglottis and the medial prolapse of the arytenoids. The laryngoscope blade’s position in the vallecula has elevated the epiglottis and moderated the appearance of supraglottic collapse



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Fig. 2
Immediate postoperative appearance of the patient from Fig. 1 after aryepiglottic fold division. Note the expanded supraglottic airway. Removal of redundant arytenoid soft tissue could be subsequently performed to further open the airway


Laryngomalacia is most easily diagnosed endoscopically, with a simple bedside flexible fiberoptic laryngoscopic exam, which allows for direct visualization of the airway during dynamic respiration, from the oropharynx to the hypopharynx and larynx. Large-scale studies have shown that endoscopy is more sensitive at diagnosing laryngomalacia than radiographic evaluation [9]. Additionally, flexible bronchoscopy performed under sedation by pediatric pulmonology should be considered, because laryngomalacia may be associated with additional lower airway lesions, with reports ranging from 10–41 % of secondary lesions [10, 11]. Diagnosis of laryngomalacia in premature infants is important, as it may be a large contributor to failure to extubate, or alternatively these children may require prolonged CPAP.

Gastroesophageal reflux (GER) and laryngomalacia have been shown to be strongly correlated. In one study, GERD was found in 64 % of patients with laryngomalacia, and was significantly associated with severe symptoms and complicated clinical course including increased rates of hospitalization, poor weight gain, and the need for surgical intervention [12].



Glottis


Obstruction at the level of the glottis can be caused by a failure of recannulation of the airway during fetal development, as seen in laryngeal webs or atresia (Fig. 3), as well as by vocal cord immobility. Vocal cord paralysis can be either unilateral or bilateral. Unilateral paralysis is most commonly iatrogenic and is associated with birth trauma or repair of cardiac abnormalities. The extended course of the left recurrent laryngeal nerve exposes it to iatrogenic damage during cardiovascular surgery and esophageal surgery. Because of this, unilateral paralysis is predominantly left-sided. The right vagus nerve can be injured during placement and decannulation of ECMO cannulas [13]. Unilateral paralysis can present with a hoarse, breathy cry, and can be associated with aspiration and dysphagia. Therefore, diagnosis should be sought early, and further management should ideally involve speech therapy in joint consultation with ENT or pulmonology.

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Fig. 3
A congenital laryngeal web in an infant with 22q11.2 microdeletion syndrome

A 2014 meta-analysis estimated the rate of unilateral vocal fold paralysis after congenital cardiac surgery to be approximately 9 %, but a subset of the analyzed studies in which all patients were prospectively evaluated by laryngoscopy reported a rate of 30 % [14]. Risk of unilateral paralysis after patent ductus arteriosus ligation was reported in 5–17 % of preterm and low birth weight infants [15, 16]. Risk of unilateral vocal fold dysfunction is even higher, approximately 58 %, in infants that undergo more complex repairs such as Norwood or aortic arch reconstruction [17]. Younger age, underlying airway or genetic abnormalities are further risks, and may warrant formal airway evaluation, for instance, at the time of extubation [18]. Interestingly, left vocal cord dysfunction during exercise was demonstrated in 26 % of such former premature infants with history of PDA ligation when they were adults [19].

A majority of congenital vocal fold paralysis is bilateral. Bilateral paralysis can be congenital acquired in the early neonatal period due to hydrocephalus or Arnold-Chiari malformation, but is often idiopathic. Premature infants who required intubation at delivery may only be diagnosed with vocal fold paralysis at the time of extubation. Bilateral vocal fold paralysis causing airway compromise normally presents with high-pitched inspiratory or biphasic stridor. The cry often sounds relatively normal, and this can delay diagnosis.

Diagnosis of unilateral or bilateral vocal cord dysfunction is best accomplished either by laryngoscopy or bronchoscopy. Further evaluation of their swallowing and feeding will determine treatment options ranging from watchful waiting in patients who can maintain adequate oxygenation and avoid significant aspiration to tracheostomy in those that cannot.


Subglottis



Description/Classification


Subglottic stenosis (SGS) is defined as narrowing of the subglottic airway to <3.5 mm in premature infants and 4.0 mm in term neonates. It can be caused by neoplasms such as hemangioma (Fig. 4), but in the premature infant, it is most often iatrogenic or congenital.

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Fig. 4
Classic appearance of a subglottic hemangioma. Red irregular mass in the lateral posterior portion of the subglottis

The vast majority (~95 %) of cases are acquired due to airway trauma, most commonly endotracheal intubation. SGS without a history of airway manipulation is considered congenital. The proportion of SGS that is congenital is likely underestimated because of the frequency of intubation before formal endoscopy in the setting of respiratory distress.

Congenital SGS can be due to cartilaginous or membranous stenosis. Congenital cartilaginous SGS can be due to a flattened (short anterior/posterior diameter), elliptical (shortened lateral diameter) (Fig. 5), or a “trapped” first tracheal ring that telescopes into the subglottis, narrowing the airway. Membranous stenosis results from hypertrophy of the submucosal tissues or mucous glands and appears soft on rigid endoscopy (Fig. 6). Congenital SGS is more likely to be amenable to observation and avoidance of surgical intervention. Because it does not result from an inflammatory process, it is also more likely to be successfully treated if surgical intervention becomes necessary.

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Fig. 5
Elliptical cricoid showing narrowed horizontal diameter of the subglottis


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Fig. 6
Subglottic cysts can arise after even transient endotracheal intubation


Epidemiology


The emergence and rapid advance of the specialty of neonatology since the 1960s has allowed the survival of premature infants with their associated pulmonary diseases of prematurity. Along with the increased survival of extreme premature infants, the incidence of prolonged endotracheal intubation may increase, causing ongoing prevalence despite the measures taken to minimize risks. As the understanding of the pathophysiology of subglottic/laryngotracheal stenosis has improved, techniques designed to minimize tissue damage have been developed, and the incidence of SGS associated with endotracheal intubation has decreased.

The true incidence of SGS specifically in premature infants is difficult to quantify. Available series include all intubated neonates and fail to specify whether they are premature or term. Reported incidence of SGS in intubated neonates has decreased from 4 % in the early 1980s to 0.63 % in more recent series [20].


Pathophysiology


Several factors combine to make to the level of the cricoid cartilage in the subglottis the site of the majority of instances of acquired LTS. The cricoid is the only complete cartilaginous ring in the normal airway, thus eliminating the ability of the airway to dilate to reduce pressure on the mucosa and submucosa. Additionally, the cricoid is the narrowest portion of the infant airway, creating the greatest levels of hydrostatic pressure along a fixed-diameter endotracheal tube. Hydrostatic pressure exceeding capillary pressure creates relative ischemia and leads to mucosal and submucosal damage. Reduced thickness of submucosal tissue at the level of the cricoid also leads to early exposure of the perichondrium and subsequent increase in inflammation. In postmortem anatomical examinations of low birth weight infants, exposure of the perichondrium at the level of the cricoid is seen in as few as 8 days in many specimens. Depth and size of mucosal scarring increases with the duration of intubation [21].

The same pathophysiological process of scar formation that leads to SGS frustrates attempts to surgically treat the condition. The increased scar deposition after mucosal trauma from intubation can also occur after endoscopic and open surgical treatment.


Treatment


Tracheostomy is in most cases a successful treatment modality for subglottic stenosis, allowing normal feeding and providing a safe airway. It is associated with significant morbidity and is generally not undertaken in infants under 2000g, as complications increase in smaller patients. The overarching goal of other modalities is to either prevent tracheostomy in the first place or allow decannulation. The majority of studies investigating these techniques define success as allowing for extubation while avoiding tracheostomy or allowing for decannulation.

The technique of dividing the cricoid ring to allow for expansion of the subglottic airway dates to Réthi’s description in 1956, but was popularized by the description of the anterior cricoid split by Cotton and Seid [1]. This technique involves a midline division of the anterior cricoid lamina and first tracheal ring without graft placement. A stent, either an endotracheal tube in the nontracheotomized patient or an Aboulker or Rutter stent or Montgomery T-tube in a patient with previously placed tracheostomy, is left in place temporarily to allow for healing. In well-selected patients without significant comorbidities, the success of this operation is quite good, with extubation/decannulation rates of approximately 70% [22]. Patients with a longer total period of preoperative intubation and with multiple medical or neurological comorbidities fare worse with success rates around 40–50 % [23].

The development by Cotton and colleagues of laryngotracheal reconstruction (LTR) in the 1970s led to improvement in outcomes by combining division of the cricoid with placement of cartilage grafts harvested from the thyroid ala or costal cartilage. When compared with anterior cricoid split, LTR is more successful and reduces complications [24]. Success rates of up to 83 % are reported [25]. Outcomes of this procedure are worse in the setting of stenosis that extends superiorly to the glottis or supraglottis and in patients under 4 kg [26, 27].

Some evidence that single stage procedure (i.e., leaving an endotracheal tube in place postoperatively rather than a tracheostomy with a second procedure to decannulate) is more likely to result in decannulation when controlling for severity of disease and previous surgery [28].

Before the development of open airway reconstruction techniques in the 1970s by Cotton and colleagues, the mainstay of treatment for SGS was serial anterograde rigid dilation (bougienage). This proved unsatisfactory and was rapidly supplanted in many cases by the newer open techniques. Shearing trauma to the mucosa inherent to the technique of bougienage could induce inflammation and fibrosis and worsen stenosis. The adoption of balloon dilation coupled with newer endoscopic techniques has brought endoscopic treatment as a primary modality back to the forefront of treatment for SGS. Balloon dilation offers the benefit of circumferential compression that limits shearing forces and theoretically reduces mucosal damage and resulting in inflammatory response. As with previous dilation techniques, balloon dilation typically requires multiple procedures to establish a durable improvement in airway diameter as discussed below. This can be contrasted with open repair techniques which aim to establish an adequate airway with one procedure. Both techniques require close follow-up and serial bronchoscopy to ensure continued patency.

Early descriptions of the technique employed angioplasty balloon catheters under fluoroscopy [29]. Most surgeons currently performing the procedure currently employ bronchoscopic visualization for placement. More recently, noncompliant balloons able to deliver pressure directly to a stenotic segment without deformation have been developed and widely adopted. Reported success rates, as defined as avoidance of tracheostomy or decannulation, vary between 39 and 100 %. Studies with longer term follow-up report success of approximately 50–60 % [3032].

There are currently no studies directly examining outcomes of rigid dilation versus balloon dilation. Published studies show similar success rates between the two techniques despite the theoretical advantages of balloon dilation detailed earlier [33]. As with other airway reconstruction techniques, overall patient numbers analyzed in these studies are limited enough to make meaningful statistical analysis difficult.

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Jun 26, 2017 | Posted by in RESPIRATORY | Comments Off on Outcomes
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