Chapter 40. Airway Reconstruction

• Patient history, including prematurity, history of intubation, feeding history, prior airway surgery, and other medical conditions.
• Physical examination, including weight, stridor, voice quality and cry, craniofacial abnormalities, pulmonary status, and cardiac status.

The following tests are diagnostic:

• Posteroanterior and lateral neck and chest x-rays
• Fluoroscopy
• Computed tomography and magnetic resonance imaging
• Flexible laryngoscopy
• Rigid endoscopy and microlaryngoscopy

Advances in care of premature infants in the last few decades have resulted in increased survival rates and a new population of patients with a history of prolonged intubation. A proportion of these patients develop subglottic stenosis up to 8%, according to some reports. Further advances in endotracheal tube and ventilation management in the last 30 y have decreased the incidence of subglottic stenosis in the neonatal population to <1%. A second population of infants born with congenital subglottic stenosis has remained stable at approximately 5%. These patients provide some of the greatest diagnostic and management challenges for the otolaryngologist.

Other airway abnormalities—both congenital and iatrogenic—including laryngomalacia, vocal fold paralysis, and supraglottic and glottic stenosis, have prompted otolaryngologists to continue to refine surgical airway reconstruction techniques. These techniques are becoming further advanced with the advent of endoscopic minimally invasive surgical procedures including robotic assisted endoscopic airway reconstruction on the horizon.

Subglottic Stenosis

The incidence of congenital subglottic stenosis is approximately 5%. The cricoid cartilage develops abnormally and may be elliptical or flattened in shape, causing cartilaginous stenosis. The remainder of subglottic stenosis is considered to be iatrogenic—airway intubation with large tube size relative to airway diameter and duration of intubation both playing roles. Host factors also play a significant role, however, because some children intubated for a very short time develop subglottic stenosis, whereas others with a prolonged intubation history do not.

Acquired subglottic stenosis more often involves soft tissue stenosis in contrast to the congenital form, which results in cartilaginous stenosis. Pressure is considered to play a role, causing initial mucosal edema and inflammation with subsequent ulceration and finally fibrosis (Figure 40–1). Other factors may exacerbate stenosis development such as gastroesophageal reflux disease (GERD) and infection. The characterization of stenosis during diagnostic endoscopy, including the location, severity, and length of the stenosis, is extremely important and helps to direct management options and predict outcomes.

Laryngomalacia

Laryngomalacia is the most common cause of neonatal stridor (54–75%). The disorder is characterized by reduced laryngeal tone, shortened aryepiglottic folds, and supraglottic collapse causing prolapse of structures into the airway on inspiration. Laryngomalacia is classified into three main types based on the anatomic portion of the supraglottic structures that is prolapsing, although any combination can coexist.

Two main theories of etiology exist. The first proposes that immature cartilage lacks the stiff structure of more mature cartilage. The second theory suggests immature neural innervation, which is a form of hypotonia. Laryngomalacia can be exacerbated by other entities such as GERD, with a coincidence of up to 80%.

Vocal Fold Paralysis

Vocal fold paralysis is the second most common cause of stridor in neonates after laryngomalacia, accounting for 10% of congenital lesions of the larynx. This condition may be congenital or secondary to an abnormality along the course of the recurrent laryngeal nerve. Vocal fold paralysis is bilateral in up to 30–62% of cases. The most common etiology is secondary to hydrocephalus from a malformation such as Arnold-Chiari. Protrusion of intracerebral contents through the jugular foramen causes stretching of the vagus nerve. Intubation and birth trauma can lead to compression or stretching of both recurrent laryngeal nerves in the neonate. Iatrogenic causes of vocal fold paralysis include cardiovascular surgery and repair of tracheoesophageal fistulas. Once the primary cause has been addressed, the paralysis should resolve. For idiopathic vocal fold paralysis, surgical intervention may be required.

Glottic Stenosis and Supraglottic Stenosis

Glottic stenosis is generally iatrogenic, resulting from either traumatic intubation involving a similar pathogenesis as subglottic stenosis or prior laser procedures on the airway such as CO2 laser excision of a papilloma. The etiology of supraglottic stenosis may also involve prior airway laser surgery or previous open airway procedures involving long-term indwelling stents with subsequent granulation tissue and fibrosis formation. GERD may also play a role in both of these diagnoses.

Laryngeal Web

Laryngeal webs can be either congenital or acquired secondary to prior airway procedures, intubation, or infection (Figure 40–2). Congenital laryngeal webs are rare malformations in which abnormal fibrous tissue is formed between two intrinsic structures of the larynx. Congenital webs are considered a form of laryngeal stenosis or atresia and warrant further evaluation for other congenital conditions. The pathogenesis of acquired laryngeal web generally involves development of an inflammatory process in reaction to the initial insult, with subsequent maturation and scar formation.

Laryngeal Cleft

Laryngeal clefts are defects in the larynx that arise from the failure of fusion and/or incomplete development of the tracheoesophageal septum. They can be classified based on extent. Type I clefts are defects in the supraglottic interarytenoid region that extends no further than the level of the true vocal folds. Type II clefts extend below the level of the true vocal folds. Type III clefts involve a complete defect of the cricoid cartilage, and type IV clefts extend into the posterior wall of the thoracic trachea.

Advances in airway management of the premature infant over the last 30 y have brought incidence rates of subglottic stenosis from 8% down to <1%. Low-irritant endotracheal tubes, nasal endotracheal intubation, and appropriately sized endotracheal tubes can reduce the risk of developing subsequent airway stenosis. Awareness of the dangers of aggressive laser use in the airway has also contributed to decreased rates of iatrogenic airway lesions such as glottic stenosis and laryngeal web formation.

Symptoms and Signs

Stridor is one of the foremost features of airway pathology. A more typical presentation of acquired subglottic stenosis, however, may be of a premature infant with a history of intubation that failed on several attempts at extubation in the intensive care unit. For an older child with an initially less-severe airway lesion, voice changes, feeding difficulties, or progressive respiratory symptoms may develop.

Imaging Studies

Posteroanterior neck and chest x-rays can be helpful in diagnosing some airway lesions. Airway fluoroscopy may demonstrate coexisting pathology, such as tracheomalacia, but is dependent on the expertise of the radiologist for the diagnosis. Preoperative barium swallow is recommended if a child has a history of feeding difficulties. Computed tomography scanning or magnetic resonance imaging can provide information on both the severity and the length of the stenoses, but should never replace endoscopic evaluation. Imaging studies may also be helpful in diagnosing tracheal compression secondary to a vascular lesion.

Special Tests

The association between airway pathology and GERD has been documented. Most airway surgeons currently recommend a preoperative evaluation for GERD for patients undergoing open airway procedures. The study of choice for diagnosis is a dual-channel pH probe. This test involves a probe in the pharynx (above the upper esophageal sphincter) and in the esophagus (above the lower esophageal sphincter) for detection of acid over a 24-h period. If GERD is found, medical therapy for 3 mo is recommended before considering airway surgery. If a repeat pH probe is still found to be positive, antireflux surgery is recommended before considering airway surgery.

Special Examinations

Flexible Endoscopic Evaluation of Swallowing

Flexible endoscopic evaluation of swallowing is recommended for patients undergoing laryngotracheal reconstruction. The test can determine whether there is evidence of laryngeal penetration, premature spillage, aspiration, hypopharyngeal clearance, hypopharyngeal pooling, or laryngeal and hypopharyngeal sensation. In a study of 255 patients undergoing flexible endoscopic evaluation of swallowing, airway reconstruction plans were altered in 15% of patients after identifying poor airway protective mechanisms. This planned alteration resulted in G-tube placement for some patients; for other patients, planned surgical reconstruction was modified with the goal of preventing both compromised postoperative recovery secondary to aspiration and the inability to maintain adequate nutrition.

Flexible Endoscopy

Preoperative dynamic view of the airway is essential when contemplating airway reconstruction. It is important to rule out possible synchronous lesions such as vocal fold paralysis or laryngomalacia, both of which are difficult to diagnose when the child is under anesthesia, even if allowed to breathe spontaneously.

Rigid Bronchoscopy and Microlaryngoscopy

Preoperative endoscopy is mandatory to assess the characteristics of a patient's airway pathology. A standard grading scale has been devised based on stenosis of the airway lumen: (1) Grade I: <50% stenosis; (2) Grade II: 51–70%; (3) Grade III: 71–99%; and (4) Grade IV: 100%. This scale, although still somewhat subjective, is an attempt to provide an objective parameter of stenosis severity. Other important characteristics to consider in the preoperative endoscopic examination include the length of the stenosis, proximity of extension to the vocal folds, and the exact location of involvement whether anterior, posterior, or circumferential. All these factors are important in planning surgery and predicting outcomes.

Pulmonary Function Tests

A patient's preoperative pulmonary status is an important indicator of the airway reconstruction technique that should be used. Patients with poor pulmonary reserve are not candidates for certain airway reconstruction procedures. Many of these patients are former premature infants and may have an element of chronic lung disease, the severity of which should be identified before proceeding with open airway reconstruction.

Voice Evaluation

Although most previous studies have evaluated only postoperative voice quality after airway reconstruction surgery, ideally, a preoperative examination would add value for comparison. Initial evaluation would include assessment of the child's overall communicative ability, potential for voicing, and the use of any form of alternative communication. Standardized measures of pediatric vocal parameters including the pediatric voice handicap index may assist in assessment of pre-/postoperative vocal changes.

The differential diagnosis of subglottic stenosis is extensive and reinforces the importance of preoperative endoscopy. It is also important to consider the possibility of synchronous lesions. Diagnoses to consider include laryngomalacia; vocal fold paralysis; laryngeal web, cyst, or cleft; laryngocele; subglottic hemangioma; tracheoesophageal fistula; tracheal stenosis; tracheal compression secondary to a vascular anomaly; and primary tracheomalacia.

Subglottic Stenosis

Historically, the treatment of symptomatic subglottic stenosis has involved three options: (1) tracheotomy, (2) endoscopic management with laser and dilation for mild to moderate lesions, and (3) airway expansion surgery for severe lesions. Observation with medical therapy is reserved for mild lesions with intermittent, nonprogressive symptoms.

Tracheotomy

Tracheotomy continues to be a mainstay of treatment, although most surgeons see this treatment option as temporary, with the eventual goal being decannulation either with or without airway expansion surgery. Tracheotomy is not without complications, however, and requires a significant amount of education about and resources for postoperative care, which can sometimes overwhelm parents. Psychosocial effects on child development also make the tracheotomy a less than ideal permanent treatment.

Anterior Cricoid Split

The anterior cricoid split was developed in an effort to avoid tracheotomy in a specific population of patients: premature infants weighing at least 1500 g without significant confounding cardiac or pulmonary compromise and evidence of anterior subglottic stenosis on bronchoscopy. In this procedure, the anterior cricoid cartilage is divided in the midline, and the incision is extended superiorly through the lower third of the thyroid cartilage and inferiorly through the first and second tracheal rings. The existing endotracheal tube is removed and replaced with a larger diameter tube that is used as a stent for 7–10 days. Steroids are given at 1 mg/kg/d 24 hours before extubation and for 5 days postoperatively. The intended outcome is for a fibrous band to form at the incision site, causing the airway to stay expanded even after stent removal. The success rate of the procedure is reported to be between 70% and 80%. There has been concern that the procedure may disrupt future cartilage growth, but this concern has not been demonstrated thus far.

Airway Expansion Surgery

In older children, the mainstay of airway expansion surgery has been to divide the stenotic area with placement of a cartilaginous graft. Although general principles apply to all laryngotracheal reconstruction procedures, the unique characteristics of each patient's lesion and overall health determine the specific procedure appropriate for that patient.

Single-Stage Surgery

The trend has been toward single-stage reconstruction, meaning that the tracheotomy is removed at the time of expansion surgery with short-term postoperative stenting (7–14 days) with an endotracheal tube. Single-stage reconstruction is not appropriate for all patients, however, especially those with more severe stenoses (Grades III and IV) or with poor pulmonary reserve. Single-stage reconstruction also requires prolonged hospitalization in an intensive care unit and immobilizing the endotracheal tube for the entire postoperative healing period. In the case of younger children, this prolonged immobilization may necessitate heavy sedation or paralysis, which can create complications such as atelectasis or narcotic withdrawal. Endotracheal tube air leak has been used as a prognostic indicator for successful extubation. Leak pressures of <20 cm H2O are associated with successful extubation.

Multistage Surgery

Multistage airway expansion procedures are generally reserved for children with more severe lesions or with confounding cardiac, pulmonary, or neurological compromise. These procedures involve cartilaginous grafting and indwelling stents, but the tracheotomy is retained and not removed until after stent removal. Division of the lateral cricoid walls without graft placement may allow for even greater expansion of the subglottic lumen. Sleep studies using a capped tracheotomy may also be helpful in assessing potential decannulation success.

Cartilage Grafts

The classic cartilage graft used is costal cartilage, but hyoid, thyroid, and auricular cartilage have also been tried. The initial concern about using cartilage grafts was that they may not survive, but histological studies have demonstrated excellent survival and growth over time. Important graft properties are as following: (1) it is of the correct depth so as not to protrude into the airway, (2) the perichondrium is left intact and faces the lumen, and (3) the graft is adequately secured. Traditionally, grafts have been sutured into position, although newer techniques such as fibrin glue and miniplate fixation have also been tried. The classic anterior costal cartilage graft is shaped like a boat with flanges, which, when the graft is inserted into the anterior cricoid incision, are flush with the lateral native cricoid ring. Caution must be taken that the graft does not protrude into the lumen, thereby compromising the lumen diameter. Newer techniques have now been described for endoscopic placement of cartilage grafts to address the posterior component of circumferential subglottic stenosis or as treatment for bilateral vocal fold immobility.

Stenting

Patients who undergo posterior cartilage grafting for posterior stenosis generally require a longer period of stenting than patients who undergo anterior grafting alone. Long-term stenting can be associated with significant complications. Many types of stents have been used, leading surgeons to conclude that no one stent necessarily guarantees a complication-free recovery and healing period. The most commonly used stents include rolled silicone sheeting (the “Swiss roll”), polytef tubes (eg, Aboulker or Cotton-Lorenz), and preformed hollow silicone tubes (eg, Montgomery T-tube.)

The optimal stent duration to maximize healing and avoid complications is controversial. For anterior cricoid splits or single-stage laryngotracheal reconstruction with an anterior cartilage graft, a duration of 7–10 days is considered adequate. For posterior cartilage grafts, a stent duration of 2–8 weeks has been recommended. For multistage procedures, stents have been kept in place from several weeks to over a year. Because of the many possible complications of indwelling stents, the most rational approach involves limiting stent duration; ideally, technically adequate expansion surgery should not require long-term stenting. Other medical conditions, such as diabetes and chronic steroid dependence, that may impact healing should also be considered during surgical planning.

Decannulation

The decannulation rates of all open airway expansion procedures that include Grades II–IV range from 37% to 100%. Newer techniques are being developed to prevent restenosis, which is the most common reason for decannulation failure. Fibroblast inhibitors including mitomycin-C and 5-fluorouracil (5-FU) have been used with mixed initial results. Other, more extensive procedures designed to remove rather than expand the stenotic segment have also been developed, including cricotracheal resection, slide tracheoplasty, and even tracheal homograft transplantation.

Cricotracheal Resection

Cricotracheal resection was originally reserved for patients who failed initial laryngotracheal reconstruction with grafting, but it is now being implemented as a first-line treatment for some patients with severe (>70% luminal obstruction) and even moderate stenoses. The procedure involves resection of the entire anterior cricoid arch with preservation of a posterior mucosal flap along the posterior cricoid plate. The normal trachea is then transected and telescoped into the posterior cricoid plate and secured with sutures to the mucosal flap and thyroid cartilage. Involvement of the vocal folds is a contraindication, and generally, a superior margin of 3 mm is recommended for success. Inferior resection margins have extended as low as the second tracheal ring, with the longest reported resection length being 3.0 cm. A tension-free anastomosis is critical for success and a suprahyoid release has been used to achieve this. Care also must be taken to avoid injury to the recurrent laryngeal nerves. A subperichondrial tracheal dissection is recommended to avoid nerve injury. Stenting may involve a single-stage or multistage procedure, with a duration ranging from 1 wk to 3 mo. Decannulation rates of > 90% have been reported in patients with a history of failed decannulation after prior laryngotracheal reconstruction. Decannulation rates after primary cricotracheal resection in Grades III and IV stenoses have been reported at 95%.

Slide Tracheoplasty

Slide tracheoplasty has been used for congenital long-segment tracheal stenosis, which is often associated with a pulmonary artery sling. The principles of slide tracheoplasty involve tracheal transection at the midpoint of the stenosis with an anterior midline incision of the distal tracheal segment and a posterior midline incision of the proximal tracheal segment. The segments are then telescoped and sutured, ideally doubling the tracheal circumference and quadrupling the cross section of tracheal lumen.

Balloon Laryngoplasty

Historically, airway dilation has been performed using rigid bougienage instruments that exert considerable sheering forces across the area of stenosis. These techniques were avoided due to the trauma created by these procedures. More recently, balloon laryngeal dilators have become available that apply controlled radial pressure to the stenotic area. Variable sizes of balloons may be used to match airway size, and pressure can be applied up to 20 atmospheres. Reports, though preliminary, have shown effectiveness of balloon laryngoplasty in both the primary treatment of subglottic stenosis as well as with dilation of restenosis after primary airway reconstruction surgery. Balloon laryngoplasty may serve to stabilize airway stenosis before definitive surgical intervention or even obviate the need for more invasive treatments.

The majority of children with laryngomalacia can be managed conservatively. Rarely, a child with significant cardiac or pulmonary compromise or failure to thrive may need surgical treatment. Supraglottoplasty is the primary operation for treating laryngomalacia. Tracheotomy is considered for children who fail supraglottoplasty or infants with multiple medical problems that warrant tracheotomy for reasons in addition to airway compromise. Patients should always be evaluated for GERD before undergoing supraglottoplasty since comorbid rates up to 80% have been demonstrated and GERD compromises postoperative healing.

Supraglottoplasty may be performed with the CO2 laser, microlaryngeal instruments, or a laryngeal microdebrider. The technique is tailored to the type of laryngomalacia that exists in the particular patient. A wide-mouthed laryngoscope (eg, a Lindholm laryngoscope) may be helpful in providing the best view of the supraglottis. The procedure is usually performed under general anesthesia with spontaneous ventilation. The three most common techniques include (1) trimming the lateral edges of the epiglottis, (2) releasing foreshortened aryepiglottic folds, or (3) excising redundant arytenoid mucosa. Care must be taken to avoid lasing or excising adjacent surfaces to prevent scar formation; overly aggressive surgery can also lead to an increased risk of postoperative aspiration. Most patients can be extubated at the end of the procedure, and often a short course of postoperative steroids is given.

Posterior glottic stenosis and bilateral vocal fold paralysis may often be difficult to distinguish and can have similar presenting symptoms. Electromyogram testing can be included as a part of the endoscopic evaluation to confirm vocal fold innervation. Tracheotomy is an option for both diagnoses, but is generally not considered an optimal long-term solution. Endoscopic procedures such as partial or complete arytenoidectomy, cordotomy, and partial cordectomy have been used in small series of pediatric patients with varying success rates. The other functions of the larynx including airway protection may worsen with any of these procedures, thereby increasing the risk of aspiration. Open or endoscopic procedures with posterior cartilage graft placement may also be used.

Laryngeal webs can be challenging to address surgically. Symptomatic thin webs can be treated endoscopically with laser excision and application of topical mitomycin-C. Thicker webs generally require laryngofissure with keel placement and a short-term tracheotomy for definitive repair.

Type I laryngeal clefts may initially be treated conservatively with thickening of feeds and sometimes a gastrostomy tube placement. Proton pump inhibitors are administered to treat presumed coexisting reflux disease. For patients who fail conservative therapy with worsening aspiration symptoms or respiratory deterioration, some advocate surgical closure of the cleft. Less-invasive endoscopic techniques are currently favored over open neck approaches. Sutures are placed strategically in order to reapproximate the edges of the mucosal defect and often CO2 laser is employed to denude the mucosal edges to encourage secondary scarring of the cleft.

Complications can be grouped into three general categories: intraoperative, early postoperative, and late postoperative. Complications are more likely in patients who have severe initial lesions that require more extensive procedures.

Intraoperative Complications

Intraoperative complications can include either pneumothorax (usually secondary to costal cartilage graft harvesting with violation of the pleura) or vocal fold paralysis (usually secondary to dissection around the trachea). Extreme care should be taken when dissecting around the pleura or recurrent laryngeal nerve to avoid injury.

Early Postoperative Complications

Endotracheal Tube and Stent Displacement

Early postoperative complications can be related to endotracheal tube or stent displacement such as subcutaneous emphysema, pneumothorax, or pneumomediastinum. Care should be taken to secure endotracheal tubes or other stents to avoid these complications. Seroma or wound infection can also occur. Some surgeons recommend empiric or culture-directed antibiotic therapy during the postoperative period.

Atelectasis

Atelectasis (with the potential to develop pneumonia) secondary to prolonged intubation, prolonged sedation, and paralysis, as well as narcotic withdrawal, is also a significant postoperative concern. The surgeon and intensive care unit staff must balance the risk of stent dislodgement with the risks of sedation and paralysis. Postoperative care is currently not standardized. After experiences with accidental extubation, some physicians have found alternative airway management methods to avoid reinstrumentation of the airway (eg, the use of bilateral positive airway pressure). Other physicians have recommended an interrupted schedule of paralysis and narcotics or avoidance of all pharmacological restraints in order to avoid side effects. Prolonged nasotracheal intubation can also cause alar necrosis if vigilant daily inspection of the nose and endotracheal tube taping is not performed.

Other Complications

Patients may also experience dysphagia, aspiration, and even failure to thrive postoperatively secondary to indwelling stents. Adjusting the stent position can sometimes resolve symptoms. Some children may require feeding tube placement until stent removal to allow for adequate nutritional support.

Late Postoperative Complications

Granulation Tissue Formation and Stenosis

Late complications can include granulation tissue formation at the stent tip and glottic or supraglottic stenosis. Cartilage grafts can also prolapse into the airway, causing restenosis. These complications may be avoided if routine postoperative endoscopy is performed at regular intervals. Some physicians advocate empiric postoperative GERD therapy to eliminate gastroesophageal reflux as a possible cause of either postoperative granulation tissue formation or stenosis. Posterior glottic stenosis may require expansion surgery with a posterior cartilage graft.

Problems with Voice Quality

Voice quality postoperatively may worsen and can be secondary to anterior commissure asymmetry, formation of a glottic web, or vocal fold scarring. Care should be taken intraoperatively to avoid incision of the anterior commissure. Reconstruction with keel placement can be considered if there is no improvement with conservative measures. Postoperative voice therapy may be indicated since delays in language and communication skills can be a source of significant morbidity for patients and their families.

Tracheocutaneous Fistula

A persistent tracheocutaneous fistula is another potential complication after a long-standing tracheotomy and may require repair with excision of the epithelial-lined tract.

Suprastomal Collapse

Suprastomal collapse can occur in patients with long-standing tracheotomies and may require rigid support with cartilage.

Arytenoid Prolapse and Supraglottic Collapse

Arytenoid prolapse may occur, most commonly after cricotracheal resection or extensive laryngotracheal expansion procedures. A partial arytenoidectomy may be required, although the potential increased risk of aspiration should also be considered. Postoperative supraglottic collapse can be an extremely challenging problem.

Inability to Decannulate

An inability to decannulate secondary to restenosis is the most devastating late complication and is more common in Grades III and IV stenoses. Revision airway surgery may increase decannulation rates.

The success of airway reconstruction techniques is determined by many factors such as the initial severity of the lesion, other patient comorbidities, and the technical expertise and experience of both the surgeon and intensive care unit staff; however, decannulation rates of 80–90% should be obtainable. A team approach is paramount to success. In managing these cases, patients should be counseled not to expect a one-time “fix,” but that multiple procedures including interval endoscopy will most likely be required.