1. Subglottic Stenosis
Saad A. Alsaleh

2. Introduction
Subglottic stenosis (SGS) is a congenital or acquired narrowing of the subglottic airway.
Acquired SGS is the most common acquired anomaly of the larynx in children.
The most common abnormality requiring tracheotomy in children younger than 1 year.
In the early 20th century SGS was rare.
3- Most cases occurred in adults
4- This resulted from the increased survival of low-birth-weight infants and the increased use of intubation in this population.  In addition, long term intubation became accepted as an alternative to tracheotomy

3. Introduction
In 1965, McDonald and Stocks introduced long-term intubation as a treatment method for neonates in need of prolonged ventilation for airway support.
In the 1960s, the incidence of acquired SGS began to dramatically increase in the neonatal population.
New attention on the pediatric larynx, and airway reconstruction and expansion techniques were developed.

4. Anatomy
The subglottis is defined as the area extending from the lower surface of the true vocal cords to the lower surface of the cricoid cartilage.  In adults this corresponds to approximately 10 mm inferior to the anterior commissure and 5 mm inferior to the posterior commissure. 

5. Anatomy Infant vs. Adult
At birth, the infant larynx is approximately one third the size of the adult larynx.
The narrowest portion of the airway in the older child and adult is the glottic aperture, while in the infant is the subglottis.
The infant larynx is positioned higher in the neck than the adult larynx.

6. Anatomy Infant vs. Adult
The structures of the infant larynx are more pliable and less fibrous making the infant airway more susceptible to narrowing from edema and less easily palpable.
One millimeter of edema circumferentially in the subglottis reduces the cross-sectional area by 60%.

7. Aetiology
SGS
Congenital
Acquired

8. Congenital SGS Accounts for 5% of all cases.
The third most common congenital airway problem (after laryngomalacia and vocal cord paralysis). 
Thought to be secondary to failure of laryngeal lumen to recanalize.
Divided into membranous or cartilaginous types.

9. Congenital SGS
Defined as subglottic diameter < 4.0 mm in full term infants and < 3.5 mm in premature infants.
It is considered if there is no Hx of intubation or other forms of laryngeal trauma.
Associated with other congenital malformations.

10. Acquired SGS Accounts for 95% of all cases.
Numerous causes including intubation (90%), trauma, infection/inflammation, thermal or caustic injuries to the subglottic mucosa.
All studies published after 1983 reported an incidence of neonatal SGS in intubated neonates as < 4.0%, and all studies published after 1990 reported an incidence of < 0.63% (Walner, 2001).

11. Acquired SGS
Pathogenesis: mucosal pressure leading to ulceration leading to chondritis and finally deposition of fibrous material.
Risk factors of developing SGS in intubated patients:
Prolonged intubation (most important).
Size of endotracheal tube.
Increased motion of tube.
Repeated intubations.
Birth weight less than 1500g.
Infection.
GERD.
Systemic illness, malnutrition, anemia, and hypoxia.

12. Diagnosis

13. Presentation
Children with SGS have an airway obstruction that may manifest in several ways.
If the stenosis is severe and congenital, the patient will present with airway distress at birth.
In neonates, SGS may manifest as stridor and obstructive breathing after extubation that requires reintubation.
In children and adults usually present with a history of prior intubation with symptoms of progressive shortness of breath and stridor.

14. Presentation The stridor in SGS usually is biphasic.
Depending on the severity, SGS can cause patients to have decreased subglottic pressure and a hoarse or a weak voice.
Question parents about: duration, progression of Sx, change in voice or cry, hx of prematurity, birth trauma, hx of intubation, feeding problems, recent trauma or foreign body exposure, hx of GERD.

15. Examination V/S : Assess presence of tachypnea, ↓ SpO2.
Evaluate the child's initial overall appearance:
Presence of increased breathing difficulty, especially during periods of heightened emotion.
Presence of cyanosis, suprasternal, substernal, intracostal retractions, or nasal flaring.
Evaluate presence of stridor & type.
Evaluate voice or crying quality for weakness, hoarseness, breathiness, or complete absence.

16. Examination
A complete head and neck exam should be performed on all patients.
Flexible fiberoptic nasopharyngolaryngoscopy:
Vocal cord mobility.
Reflux changes.
Subglottic abnormalities.
Other glottic and supraglottic abnormalities may be detected. 

18. Examination Evaluate the child's neurological status.
In the presence of tracheotomy, evaluate the patient's breathing while tracheotomy is occluded.
Auscultate the child's lung field and neck to elicit any airway obstructive symptoms and to evaluate the status of their pulmonary function.
Identify associated facial abnormalities such as cleft palate, choanal atresia, retrognathia, and facial deformities.

19. Radiology
the initial radiographic study used to evaluate a child with airway obstruction is an anteroposterior and lateral plain neck radiography.
Neck AP x-ray of patient with post-intubation subglottic stenosis, as shown by the narrowing in the tracheal lumen marked by the arrow.

20. Radiology Airway fluoroscopy & Ba swallow can be helpful.
CT scans and MRIs are not often used in the primary evaluation of SGS.

21. Other Important Investigations
Evaluate the presence of GERD by use of dual-channel pH probe testing.
The current criteria for diagnosing lower esophageal acid reflux is: a pH of < 4.0 for > 10% of the time.

22. Diagnosis
The gold standard for diagnosis of any laryngotracheal abnormalities is direct laryngoscopy and tracheobronchoscopy under general anesthesia.
Important things to document: 
The outer diameter of the largest  bronchoscope or endotracheal tube that can be passed through the stenotic segment.
The location and length of the stenosis.
Other separate sites of stenosis.
Other airway anomalies in infants.
Reflux changes.

23. Grading
There are two widely excepted staging systems for classifying subglottic stenosis: 
Myer-Cotton grading system.
McCaffrey system.

24. Cotton-Myer Grading System of SGS (1994)

25. Stage Description McCaffrey system (1992) I II III IV
Classifies laryngotracheal stenosis based on the subsites involved and the length of the stenosis.
Stage
Description I
Lesions are confined to the subglottis or trachea and < 1cm long II
Lesions are isolated to the subglottis and > 1 cm long
III
Subglottic/tracheal lesions not involving the glottis IV
Lesions involve the glottis

26. McCaffrey system (1992)

27. Differential Diagnosis
Congenital:
Laryngeomalacia
Tracheomalcia
VC paralysis
Cysts
Clefts
Vascular compression
Mass
Infection/Inflammation:
Croup
GERD
Tracheitis
Neoplastic:
Subglottic hemangioma
Recurrent respiratory papillomas
Foreign body.

28. Management

29. Management Medical Observation Tracheostomy
Airway expansion procedures

30. Medical Diagnosis and treatment of GERD
Pediatric consultation with primary physicians and specialists (pulmonary, GI, cardiology etc.)
Adult
Assess general medical status.
Consultation with primary physician and specialists.
Optimize cardiac and pulmonary function.
Control diabetes.
Discontinue steroid use if possible before LTR.

31. Observation
Patients (children and adults) with Cotton-Myer grade I and mild grade II SGS may be managed with close observation (Walner and Cotton,1999)
If no retractions, feeding difficulties, or episodes of croup requiring hospitalization.
Should be followed with growth curves by a pediatrician and/or neonatologist.
It is recommend to repeat endoscopy every months to measure the diameter of the airway to ensure that it is enlarging as the child grows.

32. Tracheostomy
Often the initial step in treatment of pediatric acquired SGS.
Allows these patients time to grow before definitive surgical treatment is performed.
Cotton and Walner recommend waiting until the infant is at least 10 kg before performing airway reconstruction. 
Allow for optimization of pulmonary function in patients with BPD
Often not performed in infants with congenital SGS.
2-5% mortality in children (Lesperance, 1996)
Accidental decannulation and plugging

33. Airway Expansion Procedures
The site, grade, and length of stenosis are the major factors in determining which surgical procedure will be used for reconstruction.
The goal is to maintain vocal function and allow for early decannulation with subsequent unrestricted activity.

34. Airway Expansion Procedures
Contraindications:
Absolute
Tracheostomy dependent (aspiration, severe BPD).
Severe GERD refractive to surgical and medical therapy.
Relative
Diabetes.
Steroid use.
Cardiac, renal or pulmonary disease.

35. Airway Expansion Procedures
Endoscopic:
Dilatation
CO2 Laser
Open Procedures:
Anterior cricoid split
Laryngotracheal reconstruction (LTR)
Cricotracheal resection (CTR)

36. Endoscopic
Mild stenosis (Cotton-Myer grades I and II)  can usually be treated with endoscopic techniques such as dilation or CO2 laser resection.
Endoscopic dilation
Practiced frequently before advent of LTR.
Requires multiple repeat procedures.
Low success rate.
Reported success rates with endoscopic laser resection of Grade I and II stenosis range from 66-80%.

37. Endoscopic Factors associated with failure Previous attempts
Circumferential scarring
Loss of cartilage support
Exposure of cartilage
Posterior inlet scarring with arytenoid fixation
Combined laryngotracheal stenosis with vertical length >1cm

38. Endoscopic treatment of laryngeal and tracheal stenosis has mitomycin C improved the outcome? PEREPELITSYN et al, 2004
Results indicate that a statistically significant increase, from <20% to 75%, in the success rate of endoscopic treatment of acquired upper airway stenosis when topical mitomycin C is added to the treatment regimen.

39. Mitomycin Does Not Prevent Laryngotracheal Repeat Stenosis After Endoscopic Dilation Surgery: An Animal Study Eliashar et al, The Laryngoscope
Mitomycin exerts a benefit equal to that of normal saline when applied to a well established laryngotracheal stenosis in dogs and does not prevent repeat stenosis after endoscopic dilation surgery.

40. Anterior cricoid split
The anterior cricoid split (ACS) procedure was originally described for a neonate who has had multiple failed extubations instead of performing a tracheostomy (Cotton and Seid, 1980).
Strict criteria for ACS have been established by Cotton and include:
Extubation failure on two occasions or more due to laryngeal pathology
Patient weight > 1500 grams
Minimal supplemental oxygen requirements
No active respiratory infection
Good pulmonary and cardiac function

41. Anterior cricoid split
The procedure is performed after direct laryngoscopic and bronchoscopic confirmation of the diagnosis.
A vertical midline incision is made through the cricoid cartilage and first two tracheal rings as well as the lower thyroid cartilage.
This allows the cartilages to spring open and allow edematous mucosa to drain, increasing airway size.
Prolene stay sutures are placed on either side of the cricoid cartilage and the skin is re-approximated after placement of a drain.

42. Anterior cricoid split

43. Anterior cricoid split
Child remains intubated 7-14 days in ICU.
Abx and antireflux meds while intubated & steroids in the first 48 hours.
Complications include pneumothorax, pneumomediastinum, subcutaneous emphysema, wound infection, and persistent SGS.
Success rate of 75.9%

44. Laryngotracheal Reconstruction
Laryngotracheal reconstruction involves scar division with distraction of the edges by interposition of graft material (augmentation) to widen the airway lumen.
Used In older pediatric patients with higher grade stenosis.
There are several techniques depending on the location and severity of the stenosis.

45. Laryngotracheal Reconstruction
It can be performed in
2 stages with a tracheostomy and formal stenting or
In a single stage by using the endotracheal tube as a stent (single-stage LTR, SS-LTR).
Laryngeal stents include:  teflon stents [Aboulker stent (short or long)], and silastic stents(Montgomery stent).

46. Single Stage LTR
Introduced in 1991 by Seid et al who reported the use of single-stage laryngotracheoplasty (LTP).
Their approach to the airway resembles ACS; however, instead of leaving the area anterior to the fibrosis, a piece of costal cartilage was placed.
Remove ET tube when air leak at 20 cm H2O.
the procedure failed in a patient who had complete glottic and SGS (grade IV).

47. LTR with stenting For severe SGS (grade III-IV).
Introduced in 1972 by Fearon and Cotton.
Widely used.
Tracheostomy and stent in place for several weeks to months.
Zalzal and Cotton have reported success rates higher than 90%.

48. LTR with stenting
Anterior: adequate for isolated anterior subglottic stenosis.
Anterior/posterior: for circumferential or posterior SGS.
Four quadrant division: for complete SGS.

49. Aboulker Stent

50. LTR with stenting Complications: Dysphagia Aspiration
Granulation tissue
Dislodgement of stent

51. Graft material
Cartilage is preferred because it has a lower rate of resorption, are easy to carve, and are viable without a vascular pedicle.
Rib and auricular most commonly used.

52. Post-operative Care Abx Antireflux Often discharged in several days
Intensive care unit
Intensivist familiar with these cases
Abx
Antireflux
Often discharged in several days
Repeat endoscopy after 3-4 weeks for stent evaluation
Once the stent is removed, follow-up bronchoscopies are performed to confirm the stenosis has not recurred before the patient is decannulated.

53. Cricotracheal resection
First reported in 1970 and popularized in the 90s.
More technically challenging than split procedures.
This technique is indicated if there is severe deformity of the cricoid making grafting very likely to fail.
95% decannulation rate (Monnier et al., 2003)

54. Cricotracheal resection
The best candidates for CTR are patients with severe SGS (grade III-IV) without associated glottic pathologic conditions and with a margin of at least 4 mm in the healthy airway below the vocal folds and above the stenosis.
Entails removing the anterior half of cricoid lamina as well as the mucosa covering the posterior cricoid lamina.
First several tracheal rings are removed.
Two ends of the airway are brought back together.

55. Cricotracheal resection

56. Cricotracheal resection
Complications:
Anastamosis failure
Granulation tissue
RLN injury
Arytenoid prolapse
Restenosis
Wound infection
Need for further procedures
Re-intubation

57. Prevention
It is important for the primary physician, anesthatist and/or intensivist to be aware of SGS as a complication of endotracheal intubation.  This starts with education.
Choosing the appropriate size ETT should be determined by the patients age and size.
Blind intubations should always be avoided if possible.

58. Prevention
Once intubated, multiple measures should be taken to prevent the tube from moving.
There is no definitive safe period for intubation.
Antireflux medications. 

59. Thank You