Airway stenosis is a critical and potentially life-threatening condition which poses unique concerns to intubating anesthesiologists. Understanding the causes of airway stenosis can help clinicians develop plans to optimize patients before procedures and to approach difficult intubations.
Common causes of stenosis include congenital tracheal abnormalities, post-intubation injury, trauma, intra-tracheal tumor, and reactive airway disease, though other etiologies exist.1 Congenital tracheal stenosis (CTS) is a congenital disease characterized by tracheal luminal narrowing. The degree of its effect on respiration depends upon the degree of luminal stenosis, presence of concurrent or concomitant respiratory conditions (e.g., asthma, tracheal esophageal fistula), and degree of bronchial involvement.2 However, CTS is exceedingly rare, with an incidence of approximately 1 in 64,500 cases.3 Tracheal stenosis may also derive from tracheal compression resulting in regional loss of blood flow. This causes tracheal edema and subsequent stenosis. When this regional flow limitation and inflammation is secondary to compression during or from intubation, this is referred to as postintubation tracheal stenosis (PITS).4 Though CTS and, for example, PITS both cause airway stenosis, the approach to intubation in these difficult scenarios can vary due to the root causes being different.
Other causes of airway stenosis include viral and bacterial infections causing tracheitis.5 Autoimmune disorders are an additional spectrum of etiologies which can result in deposition (e.g., amyloid protein or granulomatous) in the connective tissue surrounding the tracheal lumen, resulting in tracheal stenosis. Common autoimmune etiologies include sarcoidosis, amyloidosis, and polychondritis.6 The ability to optimize such patients before intubation varies by the individual patient.
Primary tracheal tumors can cause respiratory compromise through airway stenosis. Malignant primary tracheal tumors, such as squamous cell carcinomas and adenoid cystic carcinomas may also cause airway compromise.7 Meanwhile, common benign tracheal tumors are usually either endobronchial hamartomas or squamous cell papillomas.7
In reactive airway disease such as asthma, there are structural and inflammatory changes of the bronchi and circumferential smooth muscle with the additional production of mucus and bronchoconstriction, resulting in bronchial stenosis.8 Asthma has a similar pathophysiology to bronchospasm, another form of airway hyperresponsiveness.9 Bronchospasm has been noted to occur immediately following anesthetic induction in some patients, suggestive of a drug-induced anaphylactic response.10 When a difficult intubation due to airway stenosis can be traced back to reactive airway disease, anesthesiologists will often seek to calm the reaction before
the procedure as much as possible. Nonetheless, anesthesiologists must be ready to manage anesthesia-induced reactions.
While there are multiple causes of airway stenosis that can lead to a difficult airway, the American Society of Anesthesiologists (ASA) proposed guidelines for management in their 2022 Difficult Airway Guidelines.11 In these guidelines, the ASA defines a difficult airway as an airway which creates a clinical situation in which there is difficulty or failure on the part of the experienced physician in adequately ventilating the patient. The guidelines emphasize a comprehensive pre-operative evaluation to identify and subsequently stratify the risk of airway stenosis. In patients found to have difficult airways, the approach depends on the etiology. However, broad approaches include enhanced visualization of airway during intubation attempts (e.g. lighted or optical stylets and the use of video laryngoscopes), the presence of additional equipment in the room in case of inadequate ventilation, and the consideration of supraglottic airway devices. It is recommended to identify strategies for the following circumstances: awake intubation, a patient who can be ventilated but not intubated, a patient who can be neither ventilated nor intubated, and a patient who requires emergency invasive airway rescue.11
Though there are many causes of airway stenosis, all result in the limitation of airflow and can lead to respiratory compromise. It is imperative that pre-operative risk assessment is thorough and identifies increased risk of airway stenosis whenever possible. In cases of airway stenosis leading to difficult ventilation, the ASA’s 2022 Difficult Airway Guidelines offer the most contemporary approaches to management.
References
1. Isono S, Kitamura Y, Asai T, Cook TM, Riou B. Case Scenario: Perioperative Airway Management of a Patient with Tracheal Stenosis. Anesthesiology. 2010;112(4):970-978. doi:10.1097/ALN.0b013e3181d4051a
2. Hofferberth SC, Watters K, Rahbar R, Fynn-Thompson F. Management of Congenital Tracheal Stenosis. PEDIATRICS. 2015;136(3):e660-e669. doi:10.1542/peds.2014-3931
3. Benjamin B, Pitkin J, Cohen D. Congenital Tracheal Stenosis. Ann Otol Rhinol Laryngol. 1981;90(4):364-371. doi:10.1177/000348948109000416
4. Wain JC. Postintubation Tracheal Stenosis. Semin Thorac Cardiovasc Surg. 2009;21(3):284-289. doi:10.1053/j.semtcvs.2009.08.001
5. Isaiah A, Pereira KD, Correa AG. Tracheal Infections. In: Valdez T, Vallejo J, eds. Infectious Diseases in Pediatric Otolaryngology. Springer International Publishing; 2016:163-175. doi:10.1007/978-3-319-21744-4_12
6. Bhalla M, Grillo HC, McLoud TC, Shepard JO, Weber AL, Mark EJ. Idiopathic laryngotracheal stenosis: radiologic findings. Am J Roentgenol. 1993;161(3):515-517. doi:10.2214/ajr.161.3.8352095
7. Harris C, Cao C, Croce B, Cao C. Tracheal tumors. Ann Cardiothorac Surg. 2018;7(2):317. doi:10.21037/acs.2018.02.02
8. Doeing DC, Solway J. Airway smooth muscle in the pathophysiology and treatment of asthma. J Appl Physiol Bethesda Md 1985. 2013;114(7):834-843. doi:10.1152/japplphysiol.00950.2012
9. Fredberg JJ. Bronchospasm and its biophysical basis in airway smooth muscle. Respir Res. 2004;5(1):2. doi:10.1186/1465-9921-5-2
10. Dewachter P, Mouton-Faivre C, Emala CW, Beloucif S, Riou B. Case Scenario: Bronchospasm during Anesthetic Induction. Anesthesiology. 2011;114(5):1200-1210. doi:10.1097/ALN.0b013e3182172cd3
11. Apfelbaum JL, Hagberg CA, Connis RT, et al. 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway. Anesthesiology. 2022;136(1):31-81. doi:10.1097/ALN.0000000000004002
