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 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.
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.
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.
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 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.
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.
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.
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 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 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.
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.
Bent JP, Shah MB, Nord R, Parikh SR. Balloon dilation for recurrent stenosis after pediatric laryngotracheoplasty. Ann Otol Rhinol Laryngol. Sep 2010;119(9):619–627. (Report of 10 patients with stenosis treated with balloon dilation after primary laryngotracheoplasty)
Durden F, Sobol SE. Balloon laryngoplasty as a primary treatment for subglottic stenosis. Arch Otolaryngol Head Neck Surg. Aug 2007;133(8):772–775. (Series of 10 patients who underwent balloon dilation, 7 of the patients did not require further airway procedures.)